The popliteal eminence shows that the intra-articular popliteal tendon supports posterolateral knee stability

The intra-articular popliteal tendon (iPT) is responsible for the dynamic stability of the posterolateral part of the knee joint. In this study, the involvement of the iPT in posterolateral stability in response to knee flexion was investigated anatomically. Thirty-one knees from thirty formalin-fixed room cadavers (17 male knees, 14 female knees; average age 86.9 years) were used. The knee was prepared with the distal 1/3 of the lower femur and crus and was flexed at 0°, 30°, 60°, and 90° in a special jig to limit knee rotation. The series of movements was plotted on the coordinate system using the Quadrant method. The iPT was in strong contact with a thick cartilage area, which we called the "popliteal eminence", at the lateral condyle of the femur. The average iPT angles with respect to the femoral axis were 28.78°, 49.79°, 77.74°, and 115.44° at knee flexion of 0°, 30°, 60°, and 90°, respectively. The iPT was strongly associated with the popliteal eminence at 29.5° in Type I and 27.09° in Type II knee flexion. The iPT has been conventionally regarded as a secondary restraint of posterior movement, acting as a stabilizer. However, the iPT appears to work more positively on knee joint stability because it was in strong enough contact to create the popliteal eminence. The iPT supports the femur in the posterolateral region in mild knee flexion.