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Why does distal patella articular softening happen?
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Editor’s note: Members of the Patellofemoral Foundation review and add clinical perspective to recently published studies on the causes, prevention and treatment of patellofemoral disorders. The twice monthly blogs are edited by John P. Fulkerson, MD, and can be found on www.healio.com/orthopaedics. To read all the Patellofemoral Update blogs, click here.
Orthopaedic surgeons who are familiar with knee arthroscopy in young people with chronic, resistant anterior knee pain are painfully aware of soft distal and lateral patella articular cartilage that sometimes defies all nonoperative measures — rest, time, anti-inflammatory medication, braces and limitation of activity. Lateral release cannot unload a distal patella articular lesion and can make such patients worse.
Historically, such patients have ended up without treatment and live with pain that causes dysfunction with every step in some cases, and particularly with increased activity and stairs. In short, the observation of soft patella articular cartilage may be the only finding in some young patients with chronic, debilitating patellofemoral pain.
Is it the beginning of an ongoing process?
One must ask: Is this cartilage softening the beginning of an ongoing process that will eventually lead to collapse of lateral facet cartilage as we see in older patients (mostly women)? One must also ask why does this happen and what can one do about some patients’ unrelenting, conservative treatment-resistant pain.
There are no easy answers to these questions. However, it is first important to recognize that this is a real entity. It is much more evident for orthopaedic surgeons who see many patients with resistant anterior knee pain and who ultimately chose arthroscopy for such patients.
While we cannot say for sure why this occurs, it is a problem predominantly of young women, sometimes after trauma but usually not. After seeing many such patients, sometimes who are severely debilitated, there is often but not always a close association between this focal patella articular softening and aberrant lower extremity mechanics. There is particularly excessive functional internal rotation that causes slow centering of the patella in the trochlear groove and therefore prolonged and aberrant pressure on the distal patella with progressive knee flexion and vigorous activity. The same is true if the patient has an objective chronic lateral tracking/tilt of the patella such that the patella cannot gain proper entry into the central trochlea, therefore resulting in chronic focal articular overload of the distal and lateral patella.
Lateral retinacular release
When cartilage is definitely softened on the distal and lateral patella, it is possible that complete immobilization for 6 weeks, with or without subchondral drilling to create a “healing response,” can help, even after traditional periods of rest and nonoperative measures have failed. When and only when there is objective lateral tilt of the patella onto a soft, painful lateral facet, lateral retinacular release has proven helpful in my experience.
In patients with chronic, resistant pain and objective distal/lateral patella softening, a short, steep anteromedial tibial tubercle transfer will unload the affected area and give pain relief in the majority of such patients. However, this is a big step reserved for patients with clear findings and intractable pain.
Chronic patellofemoral pain associated with objective distal/lateral patella articular softening has confounded orthopaedic surgeons for many years. It is most important that we look for this and take these patients seriously when such objective changes are noted in the patient with chronic patellofemoral pain.
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- John P. Fulkerson, MD, is a clinical professor of orthopedic surgery at the University of Connecticut School of Medicine and practices at Orthopedic Associates of Hartford in Farmington, Conn. He is also president of The Patellofemoral Foundation.
Disclosure: Fulkerson reports he receives royalties from DJO Global and is a patent holder for DJO Global.
Perspective
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Vicente Sanchis-Alfonso, MD, PhD
In my clinical practice, for the rare cases of patients with anterior knee pain resistant to conservative treatment, for whom I consider performing an arthroscopic patellar denervation to treat their pain, I find an articular cartilage softening of the distal patella frequently. I agree with Dr. Fulkerson that this is a real clinical entity especially in young women with anterior knee pain without previous knee trauma.
Moreover, I have also consistently found a severe chondropathy in the distal pole of the patella with exposed bone in patients with severe lateral patellar instability associated with severe anterior knee pain and grade D trochlear dysplasia. In these cases, after performing a sulcus-deepening trochleoplasty, according to the technique described by David Dejour, MD, to treat the instability, surprisingly the anterior knee pain also disappears. In agreement with Dr. Fulkerson, I believe the pain is related to a focal cartilage overload of the distal patellar articular surface secondary to functional maltracking or a structural alignment problem. Pain in such patients is likely coming from distal subchondral bone that is repeatedly hyper-loaded due to the cartilage damage. We must note the Maquet effect (unloading of the affected area of the patellofemoral joint) of the sulcus-deepening trochleoplasty. Of course, the same unloading effect could be achieved with a short, steep anteromedial tibial tubercle transfer, as Dr Fulkerson advises. However, I believe we must save these surgical techniques for patients with very clear clinical findings and intractable pain.
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