It is a condition in which there is a Sesamoid Bone in the lateral gastrocnemius. It is located behind the lateral (outer) Femoral Condyle. It is a normal variant in 10-20% people without any symptoms.
Continuous rubbing of the Sesamoid Bone over the lateral Femoral Condyle can cause pain. This is called as the Fabella Syndrome.
Pain and tenderness over posterior aspect of Knee, best examined when the leg is straight.
X-ray
MRI
Is indicated only when the conservative therapy as failed after a 6 month trial. In this case a surgical excision is done to relieve the symptoms.