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Am Fam Physician. 2016;93(3):170

Author disclosure: No relevant financial affiliations.

to the editor: An increasing number of overweight middle-aged and older individuals are presenting to health care professionals with knee pain. This problem has proven difficult to treat, which places into question the pathogenesis of knee pain in this population.`

Although the cause of pain may be clear in cases of severe osteoarthritis with knee swelling and limited range of motion, studies have shown that in cases of mild to moderate arthritis, there is poor correlation between radiographic findings and severity of knee pain.1 Magnetic resonance imaging (MRI) is unreliable in establishing a diagnosis, as studies in older adults found a high rate of false-positive results and incidental MRI changes in the contralateral, asymptomatic knee.2 Thus, imaging findings may have little correlation with the actual cause of the knee pain.

A number of treatments targeting pathology inside the knee joint have not been proven to be effective or only provide short-term benefit. These include oral glucosamine, injections with viscosupplementation or steroids, and arthroscopic debridement.3

Given that conservative treatments targeting intra-articular pathology in degenerative knees fail to provide consistent, enduring relief, it becomes important to focus on other etiologies of knee pain.

One condition that causes knee pain in older, overweight women is pes anserine bursitis. A few clinical studies have shown that this condition can be treated successfully with physiotherapy as well as a steroid injection into the pes bursa, which can be performed safely in the office setting.4,5

I encounter these cases routinely in older, overweight women referred for knee arthritis or meniscus tear identified on an imaging study. These individuals demonstrate maximal tenderness over the pes bursa, not on the joint line, and characteristically have quadriceps weakness. Many women who have been referred to me as candidates for knee replacement have avoided surgery with treatment of pes bursitis, which includes a self-directed strengthening program for the hip and knee, and occasionally an injection into the pes bursa. Diagnosing and treating pes anserine bursitis can potentially decrease the amount of knee arthroplasty, especially in women who undergo about 50% more knee replacements than men.6

Physicians should place pes anserine bursitis in the differential diagnosis when assessing overweight middle-aged and elderly women with knee pain. A careful history and physical examination may lead to the correct diagnosis and successful conservative treatment, thus avoiding unnecessary surgical procedures based primarily on the findings of imaging studies.

Email letter submissions to afplet@aafp.org. Letters should be fewer than 400 words and limited to six references, one table or figure, and three authors. Letters submitted for publication in AFP must not be submitted to any other publication. Letters may be edited to meet style and space requirements.

This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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