Reason: Area of lucency found on radiograph of the left knee History: Left knee pain There is a lesion within the proximal fibula extending from the fibular head into the proximal diaphysis over a total longitudinal distance of approximately 7.5 cm. The lesion occupies the majority of the width of the medullary canal and measures approximately 2.5 cm in its greatest transverse dimension in the fibular head. The lesion has a lobulated morphology. On T1 images it is slightly hypointense to skeletal muscle and near-fluid signal intensity on T2 weighted images. Following gadolinium administration, the lesion shows predominantly peripheral and septal enhancement. The lesion appears to be associated with mild cortical thinning but we see no frank cortical penetration. There are small round foci with similar signal intensity and enhancement characteristics in the soft tissues in the general the vicinity of the fibular head, some of which appear to erode into the proximal tibia.Severe osteoarthritis affects the knee, with tricompartmental osteophytes. The medial tibiofemoral compartment is devoid of articular cartilage with degenerative subchondral signal abnormality. There is moderate degeneration of the articular cartilage of the lateral tibiofemoral compartment with smaller full-thickness defects along the femur and tibia. There is also degeneration of the articular cartilage along the femoral trochlea.There is complex tearing of the medial meniscus. The ACL is not well visualized, presumably due to chronic tear. The PCL, MCL, and LCL are intact. The extensor mechanism is intact. There is a small joint effusion with a small amount of fluid extending into the semimembranosus-gastrocnemius recess. The visualized portions of the tibial and peroneal nerves appear normal.
1. Proximal fibular lesion as described above. Although the lesion does show heterogeneous enhancement, it is predominantly peripheral and septal in nature and furthermore similar appearing smaller lesions are seen in the soft tissues adjacent to the fibular head; thus we favor that this represents an intraosseous ganglion rather than an aggressive neoplasm, however follow-up with orthopedic oncology is recommended.2. Poor visualization of the ACL suggesting chronic tear.3. Severe osteoarthritis predominantly affecting the medial tibiofemoral compartment with complex tearing of the medial meniscus and other findings as described above.