Manabu Akagawa et.al. presented a case of a 26-year-old man who presented with acute right knee pain and restricted extension. Although snapping could not be reproduced due to severe pain, the snapping of the gracilis tendon could be specifically diagnosed using ultrasonography and lidocaine injection. Because of the failure of conservative treatment, surgery was performed. The distal attachment of the gracilis tendon was released, and the symptom disappeared quickly. There was no recurrence at the 10-month follow-up.
A 26-year-old man visited a nearby hospital with the chief complaint of acute right knee pain and restricted extension without any apparent cause. Intra-articular injection and drug therapy did not improve the symptom. Therefore, he came to our department the following day. The same symptoms had occurred several times since the age of 17 years, and each time, he reduced it by himself, but this time he could not. He did not have any specific sports or daily activities which cause snapping.
Physical examination showed no redness, swelling, or ballottement in the right knee; range of motion restricted to extension -20° and flexion 120° due to severe pain; and tenderness in the medial joint space and proximal part of the medial tibial condyle.
Radiographs, computed tomography, and magnetic resonance imaging showed no evidence of intra- or extra-articular abnormalities (Figures (Figures11--3).3). However, US showed snapping of the gracilis tendon. It was not possible to reproduce the snapping symptom due to pain, but when each tendon of the pes anserinus was slid manually under US, the pain was reproduced only in the gracilis tendon (). Thus, lidocaine injection was performed under US guidance. Since selective injection of the local anaesthetic to only the gracilis tendon allowed the patient to fully extend the knee without pain, SPS was diagnosed. However, the injection's effect disappeared in half a day, and severe pain reappeared. Therefore, surgery was performed.