Balazs et al (1) noted that the normal knee joint contains 5 to 8 ml of synovial fluid. This is the only normal joint in which fluid can be recognized radiographically. In the suprapatellar area this fluid can be seen in the lateral x-ray as a rec-tangular opacity running upward and forward from the edge of the articular surface of the femoral condyle (Fig. 6-1). There is a triangular mass of extrasynovial fat between the fluid and the quadriceps tendon cephalic to the patella. The suprapatellar pouch continues up on to the posterior aspect of the quadriceps and cannot be separated from it. Posterior to the synovial fluid, a further mass of fat lies ventral to the femur. Fluid may also be seen between the femoral condyles and the upper surface of the infrapatellar pad of fat. The layer of fluid here becomes continuous with that between the under surface of the triangular pad and the smooth upper surface of the tibia ventral to the tibial spine. This layer of fluid is 1 to 2 mm in thickness. In the anteroposterior view of the knee, the fluid lies medially and laterally to the joint margins of the tibia and femur. The medial and lateral ligaments form a clear-cut boundary to this fluid.
KeywordsKnee Joint Femoral Condyle Quadriceps Tendon Popliteal Fossa Synovial Cyst
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