Nodular fasciitis causing progressive limitation of knee flexion in a marathon runner: Imaging with ultrasound and magnetic resonance

摘要

A 34-year-old man was healthy until he started training for marathons. He felt pain over his right posterolateral knee whenever he ran for 1–2 km. Stair negotiation aggravated his pain. Findings at the initial visit only revealed mild tenderness of his right posterolateral thigh. The right knee plain film and initial ultrasound examination were normal. After 2 months of treatment using physical modalities and stretching, his symptoms deteriorated, with progressive limitation of knee motion and severe pain on terminal flexion (Figure 1A). Ultrasound showed a hypoechoic round tumor superficial to the posterior cruciate ligament (PCL; Figure 1B). Tracing more cranially in the horizontal plane showed that the tumor was closely connected to the femoral attachment of both cruciate ligaments (Figure 1C). The tumor was not compressible during dynamic examination, and no enhanced vascularity was detected with Doppler. Magnetic resonance imaging showed a possible intra-articular ganglion cyst in the intercondylar fossa (Figures 1D and 1E). Arthroscopy revealed intact menisci and cruciate ligaments, and the tumor was excised through an anterior approach (Figure 1F). Pathology reported a myxoid lesion with plump spindle cells, vesicular nuclei, and eosinophilic cytoplasm in a feathery pattern in fibromyxoid stroma. There were extravasated red blood cells, thin-walled capillaries, CD163+ mucinophages, and scattered multinucleated giant cells. These confirmed the diagnosis of nodular fasciitis. After the surgery, the patient remains symptom-free.