Subchondral bone edema/insufficiency fracture of patella
A subchondral insufficiency fracture is a type of stress fracture that occurs when bone underlying the cartilage in a joint is unable to bear stresses normally subjected to the joint. It usually affects the inside of the knee or the medial compartment which bears more stress. Rarely, the patella is involved especially if it has previously been resurfaced to accommodate a total knee replacement or if a graft has been obtained from it for ligament reconstruction. Pain is usually sudden in onset, not associated with an injury and continues for weeks or months. The subchondral bone shows changes detectable on an MRI. Edema is usually present in the region.