BLOG: Identify anatomical abnormalities of anterior knee pain to simplify surgical decision-making

Anterior knee pain remains a challenging condition for patients as well as orthopedic surgeons. Nonoperative treatment remains the mainstay of treatment and positive responses are typically seen with physical therapy, particular when treatment focuses on strengthening of the quadriceps muscles, especially hip and core musculature in accordance with recent evidence.

However, clinicians treating patients with this condition know some patients will fail conservative management and present to an orthopedic surgeon in search of a surgical solution. The surgeon must then determine what surgical procedure, if any, has potential to improve the patient and, most importantly, do no harm. The goal of this blog is to discuss indications for non-arthroplasty surgical options for anterior knee pain.

Surgical decision-making

While the cause of anterior knee pain is multifactorial and remains poorly understood, surgical decision-making can be simplified by the identification of specific anatomical abnormalities and concurrent conditions that may offer pain reduction and increase in function if surgically addressed.

Elizabeth A. Arendt

Robert A. Magnussen

A key step in surgical decision-making is to identify whether the anterior knee pain is related to patellofemoral (PF) load. Pain related to load is generally localized, and worsened or improved depending on the load applied to the PF joint. Patients with localized, load-related pain may be more amenable to successful surgical treatment, while diffuse, constant pain generally does not improve with surgery.

Following failed nonoperative management, the authors consider surgical treatment if localized pain is present along with evidence of focal PF overload. Overload generally occurs laterally in cases of lateral PF hpercompression syndrome, and distally in cases of patella alta. Evidence of load-related pain includes: localized cartilage damage, subchondral osseous edema on MRI, increased symptoms with flexed knee activities of other activities that load the PF joint, and a positive response to joint unloading maneuvers including rest, bracing, and McConnell taping

Excessive load

In the setting of patella alta, excessive load of the distal patella can occur due to decreased engagement of the patella in the trochlea, concentrating load on a smaller than normal area of cartilage with a resultant increase in cartilage load which may result in cartilage wear. These patients may respond positively to treatment with a distalizing tibial tubercle osteotomy that increases contact area with resultant decrease in PF pressure.

In the absence of patellar instability or significant lateral maltracking, patients with load-related lateral patellar pain can be effectively treated by reducing pressure on the lateral PF joint through treatment of a tight lateral retinaculum, which is demonstrated by increased patellar tilt on MRI or plain films or an inability to evert the lateral patella to a neutral position on physical examination.

Lateral release

Traditionally, this goal has been achieved through lateral release. However, complications including iatrogenic patellar instability have been reported. Lateral retinacular lengthening has been reported as an alternative to lateral release. Two prospective studies have demonstrated improved outcomes with lengthening compared to release in this situation and our experience with this method has been positive with good pain relief and minimal complications.

In cases with more severe cartilage loss and osteoarthritis that remains localized to the lateral compartment, a bony procedure can be considered. Partial lateral facetectomy of the patella can yield good results, particularly in cases with a large trailing lateral osteophyte, and normal extensor mechanism alignment.

In the setting of a lateralized tibial tubercle with lateral patellar tracking or patellar instability, a tibial tubercle osteotomy can be considered. Anteromedialization of the tubercle can effectively unload the lateral and distal aspects of the patella in these situations and yield excellent pain relief. This procedure is especially attractive in the setting of concurrent lateral patellofemoral arthrosis, an elevated tibial tuberosity-trochlear groove distance and patellar instability.

Critical factor

A critical factor to consider when treating patients with anterior knee pain is whether PF instability is present concurrently. Patient often present to the clinician with a remote history of a lateral patellar dislocation as a youth, without further acute injury. Later in life they present with pain and giving way episodes that may be due to pain and crepitation or due to persistent instability. This determination may not be easy and requires a detailed history and examination. Treatment of underlying patellar instability in these patients should be undertaken with caution and the patients’ full understanding that surgical patellar stabilization may not relieve pain.

Procedures designed to decrease lateral patellar translation with a medial constraint (medial patellofemoral ligament reconstruction, etc.) may increase contact pressures in the PF joint and exacerbate pain in some patients. In contrast, isolated lateral release may actually increase lateral patellar instability in some patients. If one is treating a patient with a lateralized tibial tubercle through a medialization procedure, it is useful to consider an anteromedialization rather than a straight medialization in this situation to potentially decrease contact pressures, particularly in the lateral and distal patella as described above.

With careful patient selection, certain surgical procedures can significantly improve anterior knee pain that has failed nonoperative management, particularly when pain is localized to the lateral patellar facet.

References:

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Lack S, et al. Br J Sports Med. 2015;doi:10.1136/bjsports-2015-094723.

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Elizabeth A. Arendt, MD, is professor of Orthopedic Surgery at University of Minnesota, Minneapolis, Minn.

Robert A. Magnussen, MD, MPH, is an assistant professor of Clinical Orthopaedics; Team Physician, The OSU Sports Medicine Center, Ohio State University, Columbus, Ohio.

Disclosures: Magnussen reports no relevant financial disclosures.