49-year-old male with a history of an extensive right knee injury presents with right knee pain. Surgical buttons are noted along the lateral femoral condyle and anterior margin of the tibial epiphysis. Additional surgical tunnels within the proximal tibial metadiaphysis and distal femoral diaphysis are noted. There is anterior soft tissue swelling with a thickened patellar tendon and a large suprapatellar effusion containing a focus of gas. Intra-articular calcification paralleling the articular surface of the distal femur is presumably posttraumatic in etiology.
Surgical changes of a ligament and tendon reconstruction with a large joint effusion containing a small focus of gas density. Although this may reflect recent intervention, the possibility of infection cannot entirely be excluded.