Intra-articular Fibroma of Tendon Sheath in Knee Joint Associated with Iliotibial Band Friction Syndrome: Rare Occurrence in a Teenage Girl

Iliotibial band (ITB) friction syndrome is a common overuse injury typically seen in active athlete population. A nodular lesion on the inner side of the ITB as an etiology or an accompanying lesion with friction syndrome has rarely been reported. Among such nodular lesions around knee, fibroma of tendon sheath (FTS) is a rare occurrence. All the more intra-articular occurrence is extremely rare. A 16-year-old female presented with recurrent pain and movable nodule at the lateral joint area, diagnosed as ITB friction syndrome. The nodule was confirmed as rare intra-articular FTS on the basis of histopathology findings. When nodular lesions around knee are detected on magnetic resonance imaging, a FTS could be included in the differential diagnosis. Etiology and pathogenesis of ITB friction syndrome should be revised in view of such rare presentations.