Fabella syndrome: unusual cause of posterior knee pain

Fabella Syndrome is an extra-articular cause of intermittent pain on the postero-lateral aspect of the knee caused by compression on the posterior part of lateral Femoral condyle by the Fabella bone. (Sesamoid bone in the proximal part of the lateral gastrocnemius muscle) In some cases, the sesamoid bone is replaced by fibrous tissue or the Fabello- fibular ligament. The symptoms are more commonly seen hypermobile population who commonly hyperextend their knees leading to rubbing of the Fabella or the fibrous tissue on to corresponding femoral condyle. Other than the pain at the back of the knee, Fabella is also implicated in its association with degeneration of the knee, causing instability of the knee and also in the common peroneal nerve palsy. Activity modification, analgesic medication, cortisone injections, physiotherapy and rehabilitation methods have been shown to control the symptoms but many times surgical excision of the Fabella bone is required.