Disclosures: Samuel Jacob, DO: No financial relationships or conflicts of interest

Case Description: Collegiate athlete with bilateral snapping knees.

Setting: Outpatient

Patient: A collegiate athlete presented with audible snapping with hamstring contraction. She reported painless knee snapping since childhood, with new pain and numbness of the shins and muscle fasciculations since starting college. Symptoms were exacerbated by running and soccer, relieved with rest. Physical exam did not elicit knee snapping, with otherwise normal knee exam. Prior MRI of the right knee showed edema in the anterior tibialis muscle, suggestive of strain. Assessment/

Results: Dynamic ultrasound imaging revealed invagination of the semitendinosus tendon into the semimembranosus muscle during voluntary hamstring contraction bilaterally, with associated audible “snapping” sound. No nerve impingement was seen. Patient was diagnosed with bilateral snapping knee syndrome. Physical therapy was prescribed for deep tissue massage, stretching of hamstrings, moist heat and a home exercise program.

Discussion: Snapping joint syndrome is most commonly associated with the hip, but can infrequently occur in the knee. The biceps femoris tendon is the most commonly reported cause of snapping knee, however the iliotibial band and pes anserine muscles have also been implicated. Etiology of snapping may be intra- or extra- articular, including abnormal muscle insertion, intra-articular ganglionic cysts, loose bodies, fibular exostosis, osteochondroma, meniscal tears or snapping plica. Diagnosis is made by history and physical exam, along with use of dynamic ultrasound imaging. Most patients do not have pain or discomfort with snapping and therefore do not require intervention. If snapping becomes painful and limits activities, first-line management is conservative with physical therapy targeting the muscles involved. When conservative methods fail, case reports have shown resolution of symptoms with surgical intervention.

Conclusion: Snapping commonly occurs in the hip, but is rarely reported in the knee. We present a novel etiology of snapping knee due to semitendinosus tendon invagination into the semimembranosus muscle, diagnosed with use of dynamic ultrasound imaging.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/oh-snap-a-case-of-a-collegiate-athlete-with-bilateral-snapping-knees/