Disclosures: Bryan Le, MD: No financial relationships or conflicts of interest

Case Diagnosis: We present a case of Patellar Tendon-Lateral Femoral Condyle Friction Syndrome diagnosed via dynamic ultrasound through Hoffa’s fat pad compression by a ganglion cyst.

Case Description: 19-year-old dancer presented to clinic with 10 months of right knee pain. This was initiated by a popping sensation while twisting her right leg during dance practice. Her knee buckled and she fell on her right side with immediate onset of knee pain and swelling. She continued to have 8/10 pain and reported a painless “click” in the right knee with knee extension. Her physical exam was pertinent for tenderness to palpation over the patella and index pain provoked during valgus and varus stress test.

Setting: Tertiary Outpatient ClinicAssessment/

Results: Ultrasound evaluation of the knee in full extension revealed a small ganglion cyst at the deepest portion of Hoffa’s fat pad. With active knee flexion from a fully extended position, the cyst was appreciated to “pop” past the femoral condyles, reproducing the index clicking sensation. The magnetic resonance imaging (MRI) confirmed the ganglion cyst in the Hoffa’s fat with focal edema in the superolateral aspect of the Hoffa’s fat pad, suggesting patellar tendon lateral femoral condyle friction syndrome (PT-LFCFS). She was prescribed an 8-week course of dance medicine physical therapy.

Conclusion: This case highlights that ultrasonography may be useful in diagnosing uncommon causes for PT-LFCFS.

Discussion: PT-LFCFS is due to repetitive microtrauma causing swelling and inflammation of the Hoffa’s fat pad, and it is usually diagnosed by associated static MRI findings. Here we present a case of a ganglion cyst eliciting PT-LFCFS on dynamic ultrasound during active knee flexion. There is limited literature on bedside diagnosis of PT-LFCFS via ultrasonography. This case supports the value of using bedside ultrasonography to demonstrate the source as well as mechanism of knee symptoms in real-time, thereby expediting clinical decision-making.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/dynamic-ultrasound-examination-of-patellar-tendon-lateral-femoral-condyle-friction-syndrome-exacerbated-by-a-ganglion-cyst-a-case-report/