An accessory iliotibial band insertion: a unique anatomical variant.

The iliotibial band (ITB) is considered an important anterolateral knee joint stabiliser. Its exact anatomy remains unclear with inconsistency owing to relative paucity of detailed cadaveric studies. Multiple ITB distal insertional sites have been reported, the most common and well known being a direct attachment onto Gerdy's tubercle of the anterolateral tibia. We report a rare distal insertional site not previously documented. A 50-year-old man presented with anterior knee pain. MRI showed an accessory band deep to the ITB, partially blending in with its superficial fibres. It inserted onto the anterolateral tibial tuberosity, deep to the patellar tendon insertion and inferomedial to Gerdy's tubercle. This was asymptomatic but the patient did have an underlying median patella ridge osteochondral defect successfully treated with stem cell grafting, completely unrelated to the mentioned variant. This case highlights the importance of detecting rare anatomical variants which can potentially be a source of lateral knee pain.