Snapping Medial Knee Pain In A Runner

HISTORY: A 36-year-old female runner was referred for chronic left medial knee pain and snapping. Symptoms began three years prior with no inciting trauma. No prior left knee injuries. When seen, she complained of mild medial knee pain which was described as a dull ache. No pain radiation. Symptoms were provoked with running and terminal knee extension. She had a snapping medial knee sensation with knee extension which made her pain sharper. No swelling, locking, buckling, weakness, or numbness. She was not taking any medications for pain. She tried modifying her running activity with minimal improvement. PHYSICAL EXAM: Normal knee alignment. No knee effusion or skin abnormalities. Some tenderness to palpation along the medial knee just distal to the joint line. Knee range of motion was symmetric with flexion of 130 degrees and extension of 0 degrees. Knee sensation was intact to light touch. 5/5 strength with knee flexion and extension. Special tests including patellar grind, McMurray’s test, anterior drawer, Lachman, posterior drawer, valgus stress test, and varus stress test which were negative. Visible medial knee snapping was recreated when the patient went into full knee extension with slight external rotation when standing. DIFFERENTIAL DIAGNOSIS: Pes anserine tendinopathy, Semimembranosus tendinopathy, Meniscus tear, Patellofemoral syndrome, Plica syndrome TESTS AND RESULTS: Left knee x-ray demonstrated no osseous abnormalities. Diagnostic ultrasound of the left medial knee demonstrated that the insertional semimembranosus tendon was hypoechoic and thickened. With dynamic motion involving the patient going into full knee extension with slight external rotation there was snapping of the gracilis tendon over the semimembranosus tendon at the medial joint line which recreated her symptoms. No suprapatellar recess effusion was seen. FINAL WORKING DIAGNOSIS: Distal semimembranosus tendinosis with medial knee snapping involving the gracilis tendon over the semimembranosus tendon. TREATMENT AND OUTCOMES: The patient was referred to physical therapy. Her medial knee symptoms improved and she was able to return to running. There was discussion of performing an ultrasound-guided semimembranosus or pes anserine bursa injection, but this was deferred as her medial knee symptoms were manageable.