Knee mass Note that due to technologist error, no precontrast T1 fat sat images were obtained.Tendons and ligaments: The anterior cruciate ligament and the posterior cruciate ligaments are absent. There is no osseous contusion to suggest this is acute in nature. The medial and lateral collateral ligaments are intact. The quadriceps tendon and the patellar tendon are intact.Menisci: There is maceration of the posterior horn of the medial meniscus with abnormal signal also extending into the body and anterior horn. Increased linear signal is seen through the lateral meniscus representing degeneration although no discrete tear is appreciated. Joints:There is near full-thickness loss and diffuse thinning of the articular cartilage of the medial compartment with underlying subchondral cystic changes noted in the tibial plateau. There is diffuse thinning of the articular cartilage of the lateral compartment which is to a lesser degree than medially. Severe cartilaginous thinning of the patellofemoral articulation is also noted with areas of near full-thickness loss in the medial patellar facet and throughout the femoral trochlea.Joint effusion and soft tissues: There is a moderate-sized joint effusion and small popliteal cyst. Within the subcutaneous tissues anterior to the patellar tendon is a well-circumscribed ovoid lesion demonstrating high T2 signal and high/intermediate T1 signal. The mass measures approximately 1.3 x 1.7 x 1 cm in the greatest craniocaudal, transverse, and AP dimensions. Following contrast administration, there is no significant enhancement although there may be some thin enhancement peripherally. There is no joint space extension or invasion of surrounding structures.Osseous structures: No focal marrow replacing lesions are identified. There is no fracture.
1. Subcutaneous lesion anterior to the patellar tendon suggestive of a benign cystic lesion. Alternatively, this may represent small hematoma.2. Rupture of the ACL and PCL.3. Maceration and complex tearing of the medial meniscus.4. Varying degrees of articular cartilage loss and thinning which is most severe in the medial compartment.