39-year-old male status post BKA for sarcoma, progressive pain in joint and stump MRI of the left tibia and fibula stump was performed with the field of view expanded to include the knee and distal femur. There is an approximately 1.1 cm focus of tissue within the anterior joint anterior to the anterior aspect of the lateral tibial plateau which enhances and contains dark signal on T2 weighted images, suspicious for PVNS. A small amount of fluid is present within the knee joint without frank effusion. The cruciate and collateral ligaments as well as the menisci appear grossly intact. The extensor mechanism is normal.Within the distal aspect of the stump there is increased T2 signal within the soft tissues and marrow with mild enhancement which may simply represent reactive changes although early tumor recurrence cannot be excluded purely on the basis of imaging. The remainder of the bone marrow signal is within normal limits.
1. Focus of enhancing tissue within the knee joint as described above with T2 dark signal suspicious for PVNS.2. Mild edema and enhancement within the marrow and soft tissues of the distal stump, which may simply be reactive in etiology although on the basis of imaging tumor recurrence cannot be entirely excluded.