The contact area and pressure distribution pattern of the knee. A study of normal and osteoarthrotic knee joints.

Seven knees were studied to determine the contact area and pressure distribution of the tibiofemoral joint, under various loads and at 0 degrees flexion, using the casting method and special sensor sheets. At a load of 1000N (Newton) the contact area of the knee was 11.5 x 10(2) mm2 with menisci and 5.2 x 10(2) mm2 without menisci, and the menisci occupied 70% of the total contact area. Peak pressure at 1000N was 3MPa (Mega Pascal) with the menisci and 6MPa without them. The high pressure areas were located on the lateral meniscus as well as on the uncovered part of the articular cartilage of the lateral compartment, and on the uncovered cartilage in the medial compartment. After removal of the menisci the contact area decreased to below one half that of the intact knee and the contact pressure considerably increased. These facts imply that the menisci have load bearing and load spreading functions. The contact areas were also measured in two osteoarthrotic knees and they were significantly larger than those in normal knees. In these arthrotic knees the menisci seemed to play a less significant role in transmission of weight than in the normal knees.