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Patellofemoral pain and non-contact ACL injuries

Experts discuss current practice in managing PF pain and current theories on etiology, role of hormonal status, identifying at-risk athletes.

Issue: July 2005

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Patellofemoral pain is the current preferred term for what used to be known as chondromalacia patellae. Whereas the older term implied softening or lesions in the patellar articular cartilage, the arthroscope has shown us that patients with atraumatic anterior knee pain have no consistent findings of articular cartilage damage to correlate with symptoms. In the past, the mainstay of treatment was quadriceps strengthening. New theories on the etiology of this common problem have led to changes in its management.

Carol Teitz, MD
Moderator

Moderator: Carol Teitz, MD Professor Orthopaedics and Sports Medicine University of Washington, Seattle Member of the Orthopedics Today Editorial Board Panelists: John W. O’Kane, MD Associate Professor, Orthopaedics and Sports Medicine Adjunct Associate Professor, Family Medicine Medical Coordinator, Intercollegiate Athletics, University of Washington, Seattle Bert R. Mandelbaum, MD Co-director of the Sports Medicine Fellowship Program, President of the Research and Education Foundation Santa Monica Orthopaedic and Sports Medicine Group Edward Wojtys, MD Professor, Dept of Orthopaedic Surgery Medical Director, MedSport University of Michigan Liza Arendt, MD Associate Professor and Vice Chairman, Department of Orthopedic Surgery, Medical Director, Intercollegiate Athletics, University of Minnesota Letha Griffin, MD Team Physician and Adjunct Professor, Department of Kinesiology and Health, Georgia State University Sharon L. Hame, MD Assistant Professor, Department of Orthopaedic Surgery, David Geffen UCLA School of Medicine, Team Physician, UCLA Intercollegiate Athletics Col. Dean Taylor, MD Professor of Orthopaedic Surgery, University of Minnesota and TRIA Orthopaedic Center

Carol Teitz, MD: Are female athletes at higher risk for patellofemoral (PF) pain than the general population?

John W. O’Kane, MD: Women are at higher risk for PF pain than men. Most people with PF pain report that their symptoms are aggravated by activity placing athletes theoretically at greater risk. Many clinicians caring for a mix of elite and recreational athletes find that PF pain is more common in lower-caliber athletes than those participating at an elite level. Higher-level athletes likely exhibit fewer of the etiological factors that are discussed later. The typical patient presenting with PF pain is a younger female starting or increasing a recreational exercise program including running, hiking or other moderate or high-impact weight-bearing activity. Having said that, PF pain presents in either gender, from adolescence through middle age, with symptoms aggravated by activity and also present with kneeling, squatting or prolonged sitting.

Sharon L. Hame, MD: Female athletes are at higher risk for PF pain than the general population and than their male counterparts. Anterior knee pain may be the most common complaint of female athletes. This may be due to a variety of reasons, including anatomic (both static and dynamic), training history, training regimen and muscular strength.

Col. Dean Taylor, MD: For the purposes of this question, let’s exclude patients with pain associated with obvious patellar subluxation and/or dislocation. Based on our experience at West Point, women are at greater risk for PF pain. It is a very common problem in the female athlete at all levels of sports participation from the casual recreational athlete to the elite athlete. Although this problem used to be called chondromalacia patellae, the advent of arthroscopy and MRI has shown us that there are not always abnormalities in the articular cartilage of the patella. PF pain is most often an overuse problem. We found that female cadets are more likely to seek medical attention for overuse problems, including PF pain, than the male cadets. Interestingly, male and female cadets have similar rates of traumatic injuries.

Liza Arendt, MD: Most clinicians who treat PF pain, myself included, believe that there is a higher prevalence of PF pain in females than males. This might hold particularly true for the teenage population. However, to my knowledge there are few epidemiology-based studies that support these statements.

More recently, Don Fithian’s study has shown us that males and females have an equal likelihood of dislocating their patellas but in different decades of life. His second follow-up study shows that females have a slightly higher prevalence of re-dislocation.

Depending on how you define pain, particularly pain in the absence of obvious subluxation or dislocation, diagnosis is difficult. I am not aware of studies demonstrating that females have a greater incidence of PF pain than males, though most clinicians have observed this.

What are the particular risk factors, besides gender, which place a female at risk? I’ve always felt that one reason females experience PF pain in early teenage years is that they reach full maturation at an earlier age on average than males, and the time table of their maturation from the time hormones first begin to blossom until the time that their growth plates close is very short compared to their male counterparts. During this time, their bodies are subjected to various physical changes. Although estrogen does not put on as much muscle mass as testosterone, it is also the first time that females are able to gain any kind of muscle mass. Their pelvis becomes wider, chest development begins and they gain height. These significant body changes happen over a very short period of time. Often, their muscular/coordination development does not keep pace with this physical development. This can be one reason why we see PF pain in the maturing years of a young teenage girl.

Teitz: What is/are the current theory/theories of etiology for PF pain? What are the roles, if any, of lower limb alignment in causing PF pain? What evidence is there that pronated feet contribute to PF pain?

O’Kane: Patellofemoral pain is felt to be secondary to a combination of muscular imbalance, lower limb malalignment and overuse. Although PF is extremely common, the supporting science is weak. The muscular imbalance theory implicates primarily an extensor mechanism weakness or relative weakness of the medial quadriceps (VMO) compared to lateral quads. This results in excessive lateral forces on the patella resulting in increased lateral facet contact pressures and pain. Lateral retinaculum tightness contributes to the patella-lateral tracking as does iliotibial band tightness because of its attachment to the lateral retinaculum.

Lower limb malalignment, both static and dynamic, is implicated in the etiology of PF pain. Static malalignment is measured by assessing the Q-angle. The Q-angle is defined as the acute angle between the line connecting the anterior superior iliac spine and the midpoint of the patella and the line connecting the tibial tubercle and the midpoint on the patella. Women have larger Q-angles and historically this alignment was felt to increase lateral facet contact pressures and cause PF pain. Clinically the measurement has limited value because of measurement inconsistencies, and many question the relevance of a measurement taken at full knee extension to elucidate pain that occurs through a range of knee flexion.

Dynamic malalignment is a concept that considers the knee as one link in a kinetic chain functioning from the hip through the foot. Increased lateral contact pressure and pain occur secondary to limb factors that increase knee valgus and internal rotation with flexion and loading. Skeletal contributors include femoral anteversion, valgus alignment at the knee and subtalar pronation at the ankle and foot. Ligamentous laxity increases this malalignment. Muscular imbalance contributes through relative weakness in the hip abductors and external rotators, medial quadriceps and tibialis posterior with relative tightness of the hip flexors, gastrocnemius and soleus.

While these theories are widely accepted, scientific support is variable at best.

Hame: The true cause of PF pain is unknown but may include a number of etiologies. Potential causes include patellar chondromalacia, patellar tendonitis, quadriceps tendonitis, Osgood-Schlatter’s disease, Sinding-Larsen-Johansson’s disease, plicae syndrome and patellar instability. Overall, limb alignment may contribute to anterior knee pain. An abnormally varus or valgus knee may place undo pressure on the anterior knee and patella. Gender differences in standing knee flexion and landing from jumps may account for some of the increased anterior knee pain in female athletes. Pronated feet, more common in females, may result in changes in overall limb alignment, leading to increased pain at the anterior knee. I find correcting static and dynamic pronation with orthotics and proper shoe support improves anterior knee pain in my athletes.

Taylor: Clearly, this is a multifactorial problem. Activity level, fitness level, lower extremity strength, mobility of the patella and knee joint, and lower extremity alignment are all factors. Many patients develop PF pain with an increase in activity level, indicating that this is an overuse problem. If their fitness level is low to begin with, then they are at greater risk for developing pain with increased activity. A study by Witvrouw et al. suggested that a shortened quadriceps, decreased VMO reflex response time, decreased explosive strength and increased patellar mobility were associated with PF pain in college-aged students. The more severe cases of PF pain (the ones that require surgery) are more frequently associated with rotational and/or sagittal plane malalignment.

I don’t know of any scientific evidence implicating pronation with patellofemoral pain. However, increased subtalar pronation does increase the relative Q angle of the weight-bearing knee by creating more valgus at the knee. Our experience has been that orthotics can be helpful in reducing PF pain in some patients with excessive pronation of the subtalar joint.

Arendt: From a conceptual standpoint, I divide PF pain into two categories. One is the “malalignment theory of pain” and the second is “the tissue homeostasis theory of pain.”

The tissue envelope theory of pain places pain primarily in the overuse category. Although the exact tissue(s) that are being overused can vary and continues to be speculative in most cases, the theory advocates that every individual has a tolerance of their tissues in regards to activity and repetitive stress. If one goes beyond his/her own tissue’s envelope of acceptance, it creates pain. One can expand his/her own envelope of tissue acceptance by a variety of factors similar to the treatment of overuse injuries. These include reducing or modifying certain activities, stretching and strengthening of muscle tendon units, etc.

The malalignment theory of pain recognizes that the extensor mechanism is a dynamic unit. This dynamic unit can create an imbalance/maldistribution of forces as the kneecap tracks through the trochlear groove. Again the exact tissue(s) that creates pain is not understood. However, this theory advocates that if the tissues are brought into a balance or a “correct alignment” that the pain will be reduced.

The malalignment theory of pain advocates that many of our static forms of testing are incomplete as they do not capture the kneecap in action. Therefore, even when static imaging shows a normal alignment, the malalignment theory can still prevail.

I believe that the alignment of the lower limb is well established as a variable in the puzzle of overuse type injuries. As a limb goes through repetitive activity, if the repetitive activity is increased by motion in the frontal or sagittal plane, this can add to overuse type problems. This can include pronation at the foot, varus/valgus at the knee, anteversion/retroversion at the hip, and anterior/posterior pelvic tilt.

Although we as clinicians conceptualize an ideal body alignment, we all recognize that there are multiple variations of this in the population. I believe that we have more work to do in understanding how one can keep individual alignment of a limb in balance. This is a goal of the treating physician, to give advice to the athlete or worker with PF pain syndrome. I think we recognize normal and the extremes of abnormal when we see it, but I believe that we enter into dangerous waters when we try to take what we believe is abnormal in any one individual and correct that abnormality back to a more “normal state” through surgery.

Teitz: What special tests, if any, do you include in your physical exam when you suspect the diagnosis to be PF pain?

O’Kane: The exam for PF pain should start with a gait assessment and a weight-bearing single-leg squat looking for kinetic chain dysfunction. Patients with PF pain often demonstrate hip abductor weakness (I use the term "functional Trendelenburg"), increased knee internal rotation and valgus with poor balance and rotational instability and increased unstable pronation of the subtalar joint. I find it useful to assess the medial and lateral glide with the knee flexed 20º to 30º over a towel to ensure that the patella is engaged in the trochlea and the thigh muscles are relaxed. A glide of less than one quadrant suggests a tight retinaculum. Excessive glide approaching three or more quadrants with apprehension suggests medial or lateral instability. This test often elicits pain and crepitus in the setting of PF pain. It is also useful to range the knee in a supine position palpating the PF joint to assess for the symptomatic fine to coarse crepitus more common with PF pain. Focal painful catching at the same flexion angle is more likely with a retropatellar or trochlear osteochondral or focal chondral defect.

Hame: It is very important to examine an athlete’s overall limb alignment and gait. I inspect for VMO atrophy and calf atrophy. The patella examination includes patellar mobility, apprehension and inhibition tests, palpation of the medial and lateral facets of the patella, medial soft tissue, quadriceps and patellar tendons. Hamstring tightness should be assessed as well as iliotibial band (ITB) and hip flexor tightness. I specifically look at the feet for structure and alignment. Measuring leg lengths is also important. To measure the Q-angle, I use the seated Q-angle. I may also assess the rotational mobility of the tibia.

Taylor: I perform a thorough knee exam, including an assessment of gait and alignment. Special areas of emphasis: The exam must include a hip examination to assess for increased anteversion, which can be associated with PF pain as Bob Teitge has discussed. I also look at the ITB as there is frequently a component of ITB friction syndrome associated with PF pain. Examining the knee prone is also very helpful. The quadriceps can be much more relaxed and you have a better examination of the PF ligaments, the fat pad and patellar mobility. John Feagin has taught us this part of the exam for the PF joint. Finally, in assessing patellar mobility, it is also important to evaluate superior-inferior translation, as well as medial-lateral.

Arendt: If I have a young patient (estimate age 30 or less) who presents to the clinic with PF pain without a known injury, I rarely order any tests the first visit. More specifically, I would take a thorough history trying to see if there is any inciting activity or lifestyle concern that has accompanied this onset of PF pain. I would do a thorough physical exam looking specifically for pelvic position and alignment of the lower legs. I frequently couple this with physical therapy that evaluates more specifically muscle strength and muscle synergy. From these evaluations, one makes a plan of action that typically emphasizes strengthening and repositioning-type techniques, along with the possibility of activity modification or reduction.

Teitz: In which settings do you order imaging studies of the PF joint? Which studies do you order?

O’Kane: Significant trauma or the inability to bear weight should prompt an X-ray. Patients older than 50 years and those exhibiting systemic inflammatory symptoms are more likely to have arthritis and should have X-rays. MRIs are useful in the setting of anterior knee pain with a significant effusion, which is uncommon with PF pain, and more likely with an osteochondral or focal chondral defect.

Hame: All patients with knee pain and/or injury will get bilateral knee radiographs, which include standing AP, notch views, lateral views and Merchant views. The morphology of the trochlea and patellar position can be assessed by these views. To assess chondral defects in the patella and changes in soft tissue, including the patellar tendon and quadriceps tendon, I will order an MRI.

Taylor: Initially we’ll get standard radiographs with an axial view of the PF joint (Merchant or Laurin’s). If considering surgery, we will often obtain an MRI to assess the articular cartilage and sometimes a CT scan with a cut through the PF joint in 0º, 15º, 30º, 45º and 60º of knee flexion to assess for patellar subluxation and/or tilt. A bone scan can also be helpful to localize where the pathologic changes are occurring within the knee, especially if the exam and other studies are not definitive or suggest multiple areas of injury within the knee.

Arendt: The first study that I would order would be routine X-rays that include AP and lateral standing X-rays. The lateral should be a true lateral so one could look at the trochlear groove depth and use this as an indication of potential trochlear dysplasia. This would be in keeping with the Dejour classification of trochlear dysplasia. The AP X-ray would give some indication of varus or valgus alignment. Both views would look for radiographic evidence of joint space narrowing suggesting arthrosis.

Included in the standard X-ray views should be some form of knee axial alignment. My preference is the Laurin’s view, which is taken at 20º and 60º. I use this X-ray because it is the lowest degree of flexion that one can readily take using standard radiographic technique. It is more difficult in heavy-set people or people with muscular thighs. Frequently, a 20º view is not possible.

Alternatively, a Merchant view is reasonable, which is taken at 30º and 60º.

If one looks at a sunrise view, which typically is a 45º flexion view, this does not give us as much information as any of the views taken in lower degrees of flexion and, therefore, my preference would be to use a Merchant or a Laurin view.

For those who work routinely in the PF joint, I believe that one standard X-ray technique should be used so that they become familiar with this technique as well as having your radiology techs become familiar with one technique.

If I were looking specifically for the possibility of cartilage derangement, I would order an MRI. The MRI secondarily gives you a view of the PF joint in the axial view at 0º, which gives you another indication of the degree of symmetry between the PF joint.

I rarely order a CT scan. In my practice, I do not believe it adds further information. Classically, the CT scan was used to look for tilt and subluxation. Additionally, one could use the CT scan to find the TT-TG (the millimeters between a line drawn down the center of the trochlear sulcus and the center of the tibial tubercle), which is one objective measurement of the degree of lateralization of the tibial tubercle. In my hands, I find that we have other ways to gather this information than a CT scan. A CT scan has the possibility of exposing the patient, typically a young female, to higher doses of radiation. Therefore, in my practice, this is not a test that is frequently ordered.

Although bone scans are valuable to determine the relative “angriness” of a joint, in my practice patterns, this is not frequently needed to determine a clinical pathway. I believe it should remain in the armamentarium of the PF clinician.

I believe that the most important concept of the last five to 10 years in regards to the PF joint is the concept of proximal control. This is not to contradict those who believe that the control lies distally (foot pronation vs. neutral position), but rather it’s just to increase our success in improving the patient’s envelope of function. We first began to appreciate the role of hip abductors in PF joint activities. I believe now that our concept is more global as we recognize the importance of rotatory control of the limb underneath the pelvis as being important in maintenance of a neutral position of the limb. This obviously has applications in PF joint concerns as well as other concerns about the knee (such as acute ACL injuries). This would involve an approach that is more global than just the hip abductors and might include hip extensors, gluteus medius and maximus and abdominal strengthening.

Looking at the position of the pelvis, which is another flexible joint, also adds increased opportunity to evaluate and treat limb alignment/position.

In my practice, if one looks at the typical active person, their quad strength is relatively good, and their pelvic strength, in particular, posterior strength such as gluteus medius and hip abductors is relatively poor. Therefore, I think we can get farther with strengthening activities, thereby expanding the envelope of function if one would add the pelvis to the kinematic chain upon which we are evaluating and improving function.

I typically have the patient evaluated by the therapist and seeing the therapist for a number of visits to gain a relationship with that therapist. I believe that a one-time visit rarely is enough to guide the patient in activities that will be useful for them. I believe our biggest problem with therapy is that we do not give challenging enough exercises for the particular patient. The patient views these exercises as wimpy and therefore stops doing any exercises at all. My typical program involves two to five visits, expanding the time between the visits so that the patient can go home, work on the exercises themselves, come back and interact with the therapist to see whether the exercises create pain, and their understanding of the intensity of the exercises in regards to their own personal goals.

In many of these exercises, there is a feedback loop and some observation with regard to how exercises are performed is necessary. This feedback is initially done between the therapist and the patient; however, in the ideal situation, the therapist is giving the patient ways to cue themselves into their own feedback, either by using a mirror or by using internal cues, such as looking at the position of their knee and foot, for instance.

I also believe that for our young adults, the therapists have a dual job. One is to train the patient in these exercises and the second is to be a cheerleader trying to encourage their use. Therefore, I believe we need to place more emphasis on how to make these exercises fun and challenging for our athletic population. This is the toughest task that I see facing my athletic patient population with PF pain.

Teitz: Back in the 1970s, patients with “patellae” were put on open chain quadriceps strengthening exercises. Many patients did not tolerate these exercises. What’s new with regard to the types of exercises prescribed?

O’Kane: There is debate over the usefulness of open chain (leg extension machine with foot moving) vs. closed chain (weight-bearing squat with foot fixed) exercises, with most favoring closed chain rehabilitation in the past few years. While the studies are of variable quality, a 2003 Cochrane review identified 12 trials of quadriceps strengthening with mixed results regarding efficacy and no difference between open and closed chain exercises. I prefer closed chain exercises because in my experience open chain exercises early in the rehab course are often painful. Closed chain exercises are generally more sport specific and offer an opportunity to strengthen the entire kinetic chain, addressing not only the quadriceps, but also the proximal and distal muscle groups that contribute to dynamic malalignment and PF pain.

Hame: Today’s PF pain rehabilitation programs emphasize VMO strengthening, hamstring stretching and controlled, closed chain exercises. Bracing programs in conjunction with rehabilitation have also been suggested. I find that it is very difficult for a patient to initiate and complete an exercise program. I recommend a structured physical therapy program, which not only emphasizes strengthening but also includes “hands on” therapy. It is very difficult for patients to stretch and mobilize themselves without educated help. I also emphasize no pain during rehabilitation. Any exercise that reproduces the pain should be eliminated from the program or adjusted so it is pain-free. For example, patients should perform the leg press in a pain-free range of motion. I also recommend a good icing program including ice massage to the affected area. Ultrasound and iontophoresis may be helpful in some cases.

Taylor: Open chain exercises are OK – as long as they can be done without causing pain. There are some studies suggesting that closed chain exercises result in a slightly better improvement rate, but the key is to individualize the rehab for each patient so that they can improve their strength in a way that does not cause more pain. Our physical therapists have found that some of the programs emphasizing eccentric quadriceps activation have been helpful.

Teitz: In what circumstances do you give patients a home exercise program, and when do you send them to a physical therapist?

O’Kane: Patients who are motivated with adequate pain control and who can demonstrate the exercises in the office are good candidates for a home program. Patients who don’t meet these criteria will benefit from a short course of PT to gradually introduce exercises below the threshold of pain, progress exercises at each visit and ensure that exercises are being done correctly when significant movement reeducation is required.

Taylor: Most of our patients see a physical therapist. In the Army, the physical therapists are the providers who see the PF pain patients on referrals from primary care and work closely with the orthopedic surgeons on the patients who are not improving with rehabilitation. The Army physical therapists are excellent in assessing musculoskeletal conditions and in prescribing the appropriate rehabilitation programs for patients with nonoperative conditions.

Teitz: Excluding patients with subluxations and dislocations, is there a specific group of patients in which we can expect to find articular cartilage damage in the PF joint?

Hame: It is very difficult to predict which patients will have articular cartilage defects. Many patients will have PF crepitus. I may be more suspicious for articular surface damage in patients with complaints of clicking or catching at the PF joint. An MRI might be helpful in these cases. Fortunately, great improvement in pain can be seen with patients who have cartilage defects. These patients are at greater risk for further degradation of the articular cartilage.

With regard to surgical intervention, I will rarely operate on these patients. I have a long discussion with them regarding the nature of their problem and the lack of definitive surgical and non-surgical treatment for this problem. If surgery is performed, its success cannot be solely attributed to the surgery. Forced rest from sport and proper rehabilitation may be more important factors in the success of these operations. I do make an exception for lateral femoral compression syndrome with which I have had great success with arthroscopic release and debridement of patellar osteophytes.

Taylor: In general, we obtain an MRI if the patient has had a patellar dislocation. This may not be practical everywhere, but in our population we find that a large percentage of these patients have an articular cartilage injury. Others (Stanitski et al.) have also shown that most osteochondral and chondral fragments that are associated with a patellar dislocation will not show up on plain radiographs. We are very aggressive surgically to repair these articular cartilage injuries whenever we can.

Arendt: I believe that if the patient has a history of blunt trauma to the knee, especially blunt trauma associated with continued or intermittent swelling of the knee, this is one group that I might evaluate with an MRI to look for the potential of chondral damage.

The relationship between a malaligned patella on a static X-ray view and subsequent chondral damage is a debatable point, but I believe that we are having increasing literature support to suggest that lateral malaligned patellas on standard axial X-ray views do have an increase in cartilage PF wear pattern later in life.

Also, those patients who have had an activity that places them in a bent knee activity over great periods of time have the possibility of increased chondral damage. This might specifically be people in the squat position, such as catchers in softball or baseball, carpet layers, plumbers and electricians. These are the types of categories that might have repetitive trauma over time to their kneecap joint sufficient enough to create chondral damage.

The last category is the aging population who might have isolated PF arthritis, which is frequently missed as a clinical entity. These are patients who have a satisfactory tibial femoral joint on standing films, and no axial view was taken looking for primary PF joint arthritis. If one scrutinizes the PF joint on the lateral view, one could glean the diagnosis of primary PF joint arthritis. Despite this, we certainly have ample evidence in the literature where isolated PF joint arthritis is overlooked in our aging population as a source of pain and disability.

In regard to surgical intervention for chondral damage, this is an expanding field due to our current concepts of cartilage regeneration. However, any patient with unipolar cartilage damage should fail conservative management before any cartilage intervention surgery is attempted. I say this because I have dozens of patients with isolated lesions in the PF joint who perform satisfactorily with conservative management.

In patients with an acute traumatic injury, evidence of chondral damage to their kneecap joint by some imaging study, and continued swelling of their knee, this category of patients I would surgically intervene more quickly. This frequently involves an arthroscopic removal of a loose body and debridement of a lesion of chondral damage. Depending on the lesion size and location, this might be appropriate for microfracture technique. This is probably the most aggressive cartilage regeneration procedure I would use as a first time procedure in patients with an acute traumatic injury to the kneecap joint.

In regard to when to use more advanced cartilage regeneration techniques in the PF joint, both isolated patella lesions and isolated trochlear groove lesions offer technical challenges in regard to their cartilage shape and thickness. This is a discussion that is beyond the scope of this round table, but I would caution the reader that this is a field that continues to need more study before firm recommendations can be made in regards to treatment parameters.

Teitz: When you operate on patients with PF pain, what procedures are you doing most commonly?

Hame: I rarely operate on PF pain alone. When I operate on athletes with PF pain I may perform a variety of procedures depending on the pain etiology. Surgical procedures include diagnostic arthroscopy, chondroplasty of the patella, lateral release, excision of lateral patellar osteophytes, excision of plicae and open debridement of the patella tendon for patella tendonitis.

Taylor: It is very rare for us to operate on PF pain. If there is patellar malalignment that has not responded to rehabilitation and nonoperative measures, then we will most often perform an anterior-medialization of the tibial tubercle with a lateral release as described by Fulkerson. In patients who have anterior knee pain secondary to adhesions within the knee from trauma or previous surgery, I have been influenced by Richard Steadman’s experience. In these patients, we will perform an arthroscopic anterior interval release and release identified adhesions.

Arendt: One operates on PF pain when a patient fails conservative management and the surgeon believes there is a (surgical) solution to his or her problem. In my hands, one could use debridement principles similar to treatment for tibial femoral knee pain. If a patient has continued swelling or an effusion that fails conservative management, one would have careful debridement of chondral surfaces and/or limited synovectomy that might improve that pain syndrome associated with swelling and pain.

Pain that is associated with malalignment is a broader category than I believe was intended for this round table discussion.

The single most important statement that I can teach my residents in regards to treating PF pain is to be able to say to the patient, “I have no surgical solution for your pain.” We, as surgeons, believe that we can cure through the knife, and this can be a dangerous concept. We must have objective parameters to guide our surgical decision-making.

In a patient who has pain with a physical exam that does not point to any abnormality that might explain that pain, with a normal MRI, I do not have a surgical solution. Frequently, I need to lay this out at the beginning of our conversations, and that gives them greater impetus and energy upon which to direct nonoperative management.

Before we leave the topic of pain with PF joint, there is another arm of treatment that merits consideration in certain cases. If a patient presents to me with a history of blunt knee trauma or some trivial injury that triggers the knee pain, without sufficient objective evidence to explain that pain, I consider that this is a form of chronic regional pain syndrome or CRPS. This can be subtle in presentation; most frequently patients include variable descriptions of their pain that might include the words “burning” or “prickly” type of pain. Frequently the patient doesn’t like to have bed sheets on their knee at night and kicks them off. They frequently have pain at rest and that is not related to the bent knee position such as the “theatre sign.” For these patients, I typically do a trial of Neurontin. I would start with 300 mg qhs for one week and increase it to an end dose of 900 mg (300 mg tid) at the end of a month’s time. If, at the end of a month, they are not better, I stop it. If they are better, I discuss modifying the dose in some way depending on their pain pattern and how much improvement we have seen. Additionally, one might consider the use of lidocaine patches in this patient’s profile.

Teitz: Thank you. Now let’s change the topic from patellofemoral pain to non-contact anterior cruciate ligament tears. We know that these injuries are 4 to 8 times more common in females than in males. This increased prevalence was first noted in 1995 (Arendt) leading to a meeting of interested investigators at Hunt Valley, Md. and subsequent research. You all participated in a recent 2005 symposium (Hunt Valley II) updating what is known about risk factors and current programs to prevent non-contact ACL injuries.

In the past, the possible risk factors discussed for noncontact ACL injuries included factors both extrinsic and intrinsic to the athlete. What progress has been made looking at extrinsic factors that could be modified?

Edward Wojtys, MD: I define extrinsic risk factors as those that are exterior to the athlete’s body. The major risk factor that has been discussed in this category has been the shoe/ground interface. While the degree of friction in that interface appears to be a factor in knee injuries, there is no recent research in this area that I am aware of.

Letha Griffin, MD: Extrinsic risk factors investigated previously have included braces and shoe-surface interactions. Using braces to prevent ACL injuries still intrigues investigators despite multiple studies in the 80s that were unable to demonstrate a protective effect of functional ACL knee braces on prevention of noncontact ACL injuries.

Unlike these earlier studies, within the last year two studies have been published indicating that braces may be protective against noncontact ACL injuries. The first was a study from the Steadman group evaluating the effectiveness of functional bracing to decrease knee injuries in ACL deficient professional skiers. These researchers found a significantly higher proportion of injuries in non-braced skiers compared with braced skiers (Kocher 2003). In the second study, investigators in North Carolina used a new hinge concept which features increasing resistance throughout an arc of motion such that the athlete perceives resistance at –40º of extension before the final stop to resistance occurs at –10º or –20º of extension (Yu 2004). Athletes wearing this brace were found to have a 5º decrease in knee flexion angle on landing. Since landing on an extended hip and knee has been indicated as a risk factor for injury, investigators felt that this hinge design merits further evaluation.

It is intriguing to consider having a shoe that provides adequate traction for sport performance but not so much traction that the foot sticks to the surface during cutting, pivoting and landing activities, increasing the knee’s vulnerability to injury. Unfortunately, little investigation has been done in this area in the last five years, as the trend has been to explore intrinsic rather than extrinsic risk factors.

Bert Mandelbaum, MD: The Hunt Valley I and II group discussed this topic and reached a consensus. We agreed that with regard to extrinsic factors, fields can be improved but are not necessarily associated as a major risk factor. As far as shoes go, there is no real difference except in Lambson’s study where he showed that the lateral cleat in football is associated with greater rate of ACL injury. Otherwise, there is no consensus factor.

Teitz: There is a long list of intrinsic factors being studied. What is the current understanding of muscle activation patterns that might contribute to these injuries? How do they differ between male and female athletes? What evidence is there for differences in balance or proprioception between male and female athletes?

Wojtys: In general, quadriceps muscle activation is an ACL antagonist, while activity in the hamstrings and gastroc are agonistic. There are several studies that discuss the function of the quadriceps in male and female athletes emphasizing poorer hamstring function in women. To my knowledge, there is no evidence that women have a decreased level of proprioception or balance.

Griffin: Regarding intrinsic risk factors, we know that women are generally not as strong as men. During puberty, girls’ increases in height and weight are not accompanied by significant gains in strength and neuromuscular control as occurs in boys. Moreover, as Wojtys and Huston have shown, women generate maximal torque in their quadriceps before their hamstrings in response to anterior tibial translation, thus enhancing the quadriceps negative influence on the ACL rather than enhancing the protective affects of the hamstrings (Huston). Hewett has referred to this imbalance in recruitment as part of what he calls “the quadriceps dominant” risk factor in female athletes (Ford 2003).

Hip abductor strength is also weaker in women than in men. Ireland and others feel that the lack of core strength, including hip abductor strength, results in the hip “falling into” adduction and internal rotation upon landing. This, combined with ground reaction forces results in apparent knee valgus, tibial external rotation and foot pronation – a position she termed the “position of no return,” linking it to an increased risk for noncontact ACL injuries in female athletes (Ireland 2002).

Caraffa, in the mid 90s, suggested that balance and proprioceptive training often initiated as a part of a rehabilitation program after ankle or knee injuries should also be part of conditioning programs (Caraffa 1996). He and his colleagues in Italy, as well as Wedderkopp et al. in Denmark, Myklebust and colleagues in Norway and others have incorporated balance exercises into pre- and in-season conditioning programs (Wedderkopp 1999 and Myklebust 2003). They have reported a decrease in knee injuries in athletes participating in such intervention programs when compared with controls.

Mandelbaum: In the pathokinetic chain the mechanism that leads to noncontact ACL injuries occurs during the deceleration phase of cutting and landing maneuvers, when a rotation torque in concert with a varus/valgus moment is applied to a knee that is flexed 10º to 30º. It starts with the hip in adduction. Markolf noted that both a varus moment and internal rotation moment at the knee would place the ACL at a greater risk for injury as opposed to valgus and external rotation moments. This combined loading pattern is the most detrimental with respect to injury (ie, combined loading in the sagittal, frontal and transverse planes). That is to say, greater tibial anterior translation, knee valgus-varus moments, and knee internal/external rotation moment contribute to ACL loading and ultimate tearing.

In the female athlete the quadriceps can exacerbate this situation while the hamstrings are antagonists to anterior tibial translation. Since the woman tends to decelerate and cut in more valgus, and knee extension with a greater quadriceps response and less hamstrings it is theorized that she is at greater risk.

There are differences between girls and boys with simple cutting maneuvers with respect to kinetics and kinematics for the hip and knee.

Teitz: What is the current understanding of the role of hormonal status as a risk factor?

Wojtys: Puberty appears to be a defining factor for either gender. Prior to that time, many indices of athletic performance appear to be similar. At puberty in girls, the percent muscle mass changes as does the weight distribution. Boys undergo a greater increase in percent muscle probably due to the effect of testosterone.

Recent, but yet unpublished studies, reemphasize that there is an uneven distribution of anterior cruciate ligament injuries during the menstrual cycle. While this does not specifically indicate hormones or a specific hormone, knowing that hormones determine the cycle this way implicates them indirectly.

When one examines the literature about hormone influences on ligament biology, there are many conflicting studies. During the recent Hunt Valley II consensus conference, researchers pointed out that there are two types of animals, those that have menstrual cycles and those that have estrus cycles. Trying to compare those two types of animals and the effects of hormones in those different animals is an error and probably explains why many recent studies are conflicting.

It appears that there are more injuries to the ACL in female athletes in the first half of the menstrual cycle than in the second half. This type of cycle segmentation places ovulation in the first half. While there does appear to be more injuries in the first half of the cycle, the evidence is not strong enough to consider limiting female participation at the present time.

The effect of oral contraceptives in stabilizing the female menstrual cycle and the effect this has on injury rates is quite interesting. Unfortunately, there is no definitive proof to justify the use of oral contraceptives to prevent injuries at this point in time.

The hormonal milieu of an amenorrheic athlete is quite complex. While no doubt there are short- and long-term consequences from the loss of normal hormonal fluctuations, the exact implications for injury are unknown at this time.

Griffin: Since the incidence of ACL injury in sports requiring pivoting, cutting and jump landing is higher in women than in men, it is intriguing to consider that such a gender difference may be related to hormonal influences. We know from the work of Hame and others that the ACL has estrogen, progesterone and relaxin receptor sites (Hame 2003). Furthermore, it has been reported that estrogen can decrease fibroblast proliferation and has a direct effect on collagen metabolism and behavior. However, Seneviratne and colleagues at the Hospital for Special Surgery in New York argue that the decrease in ACL fibroblast proliferation and collagen synthesis previously reported was seen at supraphysiologic levels of estrogen (Seneviratne 2004). This group, using a sheep model, found no significant difference in ACL fibroblast proliferation or collagen synthesis when animals were exposed to physiologic concentrations of 17B-estradiol.

Moreover, Hannafin and Arendt, using goats and monkeys, respectively, have shown no biomechanical differences in the ACLs from animals that underwent ovariectomy and those who underwent a sham operation (Strickland 2003, Arendt 2001).

Some theorize, however, that hormones may influence joint laxity, balance, proprioception and agility rather than affecting the ligament’s mechanical properties. More research is needed in this area.

Although the study done by Wojtys and colleagues reported a higher incidence of ACL injury during the mid-menstrual cycle, that is at about the time of ovulation when estrogen levels are low, Slauterbeck, Arendt and Moller-Neilsen have reported a greater increase in injury about the time of menses (Wojtys 1998, Slauterbeck 2002, Arendt 1999 and Moller-Neilsen 1989).

At one time, researchers thought oral contraceptives might be protective against ACL injuries. However, currently there is no universal agreement regarding the influence of oral contraceptives on ACL injuries. Prescribing oral contraceptive pills is not recommended as a prevention strategy.

Mandelbaum: Hewitt has demonstrated a kinematic change in position and balance with pubertal progression. The effect of estrogen or any other hormone on injury rate is not yet well defined. Estrogen does have an effect on collagen synthesis.

No universal agreement has been reached concerning the time in the menstrual cycle where the greatest numbers of injuries occur, although the preponderance of evidence would indicate it is in the pre-ovulatory stage.

Rather than divide a menstrual cycle into days, for research purposes, one may wish to use time blocks, such as pre-ovulatory (follicular) stage and post-ovulatory (luteal) stage.

Biomechanical studies done on the ACLs of oophorectomized animals comparing them to those of animals with normal hormonal status showed similar characteristics. However, it may be that estrogen’s effect is upon neuromuscular control factors, postural stability and proprioception.

The female athlete should not be on oral contraceptives. There is no evidence to support that they protect against ACL injuries.

There is no study that identifies the amenorrheic athlete at risk for ACL injury.

Teitz: Given that there are multiple factors that might contribute to noncontact ACL injuries in the female athlete, how can we identify the athlete at risk?

Wojtys: The areas that have been investigated in the dilemma to identify the female athlete at risk have been the anatomical, the neuromuscular and the hormonal. It appears that identifying those with neuromuscular deficiencies will be most productive for identifying the female athlete at risk. Unfortunately, at this time, we only have preliminary data from pilot studies and cannot say definitively that we can identify these athletes based on the factors we have identified thus far.

Griffin: Identifying the athlete at risk for injury centers about evaluation of the athlete’s neuromuscular characteristics – that is, does the athlete land a jump with minimal hip and knee flexion, hip adduction, knee valgus, tibial external rotation and foot pronation? Current thought would suggest that such an athlete might benefit from neuromuscular training to learn to land with hips and knees more flexed and the body centered over the lower extremity.

In a recent study from West Point, Taylor and colleagues reported that the combined risk factors of generalized joint laxity, increased BMI (1 SD above the mean) and a narrow femoral notch in a woman are associated with a high risk of ACL injury (Uhorchak 2003). One must be careful when extrapolating from this study, as although the study was well planned and executed, the population studied – West Point cadets – is a unique group. Whether information gained from this specialized population can be generalized to all athletes has not been validated.

Genetics may also be a risk factor for injury. Studies by Fowler and Harner suggest that an athlete is more at risk for injury if the athlete has a relative who has sustained an ACL injury or if the athlete has previously sustained an ACL injury (Flynn 2005, Harner 1994).

Mandelbaum: No new risk factors have been identified since 1999. Several excellent studies exploring risk factors have been published.

The incidence of ACL injuries still appears to be greater in the young female (aged 14 to 18) than male population. The incidence of noncontact ACL injuries remains greater in sports requiring cutting, pivoting, jumping and change in direction (eg, soccer, basketball, women’s lacrosse and gymnastics). With regard to anatomic factors associated with injury, there is no definite evidence that any anatomic factor is reliably associated across age groups and sexes with an increased rate of injury. A recent study suggests that body weight and size of the notch is associated with higher incidence of ACL injury.

Knee valgus or perhaps more precisely, “apparent knee valgus,” is associated with higher ACL injury rates. The position of hip and knee extension is still associated with a greater risk of injury. An eccentric quad contraction at near hip or knee extension can generate enough force to tear the ACL. There appears to be something in jump landing that can be modified to reduce non-contact ACL injuries. The knee position with jump landing, the knee position at the time of abnormal loading and how the loads are distributed across the knee appear to be important risk factors.

Teitz: Some prevention programs seem to be decreasing injury rates. Their success may be related to the types of exercise they include, the muscles targeted, their sport specificity, or who directs the program. What do you think are the key features of these successful programs? Who should implement them and at what level of sport (ie, middle school, high school, etc.)? What resources could our readers use if they wished to investigate these programs more thoroughly?

Wojtys: The successful ACL injury prevention programs in female athletes have an educational and a training component. Unfortunately, we do not know which feature is most important for the success of these endeavors. In female athletes, there appears to be a significant increase in ACL injuries in the 14- to 15-year-old age group. Therefore, it seems most appropriate to initiate the prevention programs prior to those years.

There are two very popular programs in the United States: Sportsmetrics from Cincinnati Sportsmedicine and the PEP program from Santa Monica, Calif. Both programs are available on the Internet.

Griffin: Outcome data has revealed that despite successful ACL reconstruction – that is, despite an athlete achieving a stable knee following ACL reconstruction, arthritis typically develops within seven to 10 years (Myklebust 2003, Daniel 1994 and Gillquist 1999). Hence, prevention strategies to decrease the incidence of this injury are essential if we are to prevent this long-term complication.

Current prevention programs are based on altering neuromuscular risk factors. All successful programs have one or several of the following components: a traditional strength and stretching program for the muscles of the lower extremity and core; increased awareness of injury mechanisms; balance and plyometric exercises with the latter emphasizing correct jumping and landing positions.

Although a few programs, such as the PEP program developed by the Santa Monica Group for soccer or the Heidt program have all five components, some programs emphasize only certain elements (Mandelbaum 2004 and Heidt 2000). For example, injury awareness is the primary element in the Vermont ski program, and balance and proprioception form the basis for the programs developed by Caraffa et al, Wedderkopp et al, and Myklebust et al (Ettlinger 1995, Caraffa 1996, Wedderkopp 1999 and Myklebust 2003).

Exactly how or why these programs decrease the incidence of noncontact ACL injuries is not clearly understood. Moreover, whether the programs improve muscle strength and balance or merely enhance neuromuscular control mechanisms and hence improved dynamic knee stability is not clearly known.

Compliance is essential to success. Whether it is adequate to have the program explained through a tape or whether it is essential to have an on-site educator for proper instruction has not been defined.

Moreover, during a recent meeting of many of the prominent researchers in the area of ACL prevention (Hunt Valley II, Atlanta, January 2005), those present cautioned that although present evidence on the effectiveness of ACL prevention programs is strong, it is only level II evidence not level I evidence. Additional randomized controlled trials across ages, sports and genders are needed.

All age athletes at all levels of play can benefit from prevention strategies. The peak occurrence of ACL injuries in girls appears to be in the 15- to 17- year-old range. In the boys, the age of peak occurrence appears to be a little later. The early age at which this injury occurs necessitates that players be instructed in prevention programs during childhood and early adolescence. Whether the prevention programs should be done on-site as an alternative warm-up program or whether athletes at risk should take part in special rehabilitation/conditioning programs performed in a training room setting is yet not clear. Furthermore, the optimal time to institute the program is not known. Because injuries do occur at the beginning of the season, it has been theorized that beginning neuromuscular prevention programs at least several weeks or perhaps, months prior to the beginning of the season would be beneficial. More information is needed.

Mandelbaum: Several prevention programs based on altering neuromuscular risk factors or changing biomechanics that appear to favor injury have been successful.

The rationale and importance of implementing programs is based on the consequence of ACL injury, which includes potential loss of performance and competition and arthritis at a young age.

All the prevention programs for ACL noncontact injuries center on alteration of neuromuscular risk factors but each is unique. Some are sport specific, some are general, some are age specific, some are not. Most have been designed for and tested with female athletes.

All successful programs have had one or several of the following components: agility, plyometric, strengthening and/or stretching, cardiovascular conditioning and injury awareness, that is the awareness of the at-risk behavior mechanism of injury position.

The mechanism by which intervention programs are effective (ie, biomechanical changes following training in relationship to ACL injury mechanics) is not clearly understood; however, existing evidence points to changes in balance, strength and intramuscular coordination as being possible contributors.

Program education, supervision, compliance and data collection analysis also varies. Some analyzed the biomechanical effect of their program and others gathered only data on the incidence of non-contact ACL injury following institution of the program but did not evaluate the program’s effect on the athlete’s biomechanics.

No program has reported to increase the incidence of injury to either the knee or elsewhere.

Some of the programs must be started before the season in a gym environment; others are on the field and can be used as alternative or supplemental warm-up programs.

Neuromuscular training or intervention programs may have some beneficial effect on changing motion patterns to decrease ACL strain.

We do not know what specific modifiable risk factors are associated with non-contact ACL injuries, but there appears to be something in jump landing that can be modified to reduce non-contact ACL injuries.

Many of the studies done on prevention programs, although producing good results, are not controlled randomized studies and therefore are subject to question.

There is good evidence that neuromuscular training including plyometrics, balance and technique training as well as a heightened awareness of injury biomechanics reduces ACL injury risk in female athletes. What specific exercises or sequence of exercises, or what intensity and duration of exercise is most important are still unknown.

The impact of ACL prevention programs in improving or optimizing hip and core strength ratios is still theoretical and has not been examined.

Training may facilitate neuromuscular adaptations that provide increased joint stabilization and muscular preactivation and reactive patterns that protect the athlete’s ACL from increased loading.

Teitz: What do you think are the most important future areas of research to decrease the incidence of noncontact ACL injuries?

Wojtys: At the present time, the neuromuscular factors and hormone research appears to hold the most potential for understanding the multifactorial problem of the noncontact ACL injury, especially in female athletes.

Griffin: Norway has recently established a national registry for all ACL injuries. The Hunt Valley II group felt that a similar registry in the United States was needed. As we discussed earlier, to further verify and define prevention programs, additional randomized controlled trials across ages, across sports and across genders are needed. This should be done concurrently with research to further define risk factors and mechanisms of injury.

Mandelbaum: For the future we must do the following:

• Develop age group standards for initiating prevention programs
• Randomized controlled trials between institutions in various geographic areas of the country and across all age groups and both sexes for all high-risk sports.
• Research design should strive to identify which of the components of present day prevention programs are most significant in decreasing the rate of non-contact ACL injuries.
• Evaluate the effect of each component of prevention programs on strength of key muscle groups, on muscular firing patterns and on altering landing, cutting and pivoting techniques.