Knee joint contact pressure decreases after chronic meniscectomy relative to the acutely meniscectomized joint: a mechanical study in the goat.

Several studies have shown that meniscectomy causes an immediate, acute increase in knee joint contact pressure and that changes in pressure distribution cause remodeling of bone and soft tissue. Presumably, this remodeling in turn affects contact pressures. This study tested the hypothesis that medial compartment contact pressure increases immediately after medial meniscectomy and then decreases with time. Supporting hypotheses regarding medial compartment contact area and lateral compartment pressures also were tested. Unilateral medial meniscectomy was performed on seven adult goats. Four or 8 months later, contact pressure and area were measured in vitro in the involved joints, as well as in the contralateral joints, before and after removal of the meniscus. The medial compartment pressures of the chronically meniscectomized joints were significantly less than those of the acutely meniscectomized paired joints but remained significantly greater than those of the intact joints. For the 4 and 8 month groups combined, the mean pressures of the acutely and chronically meniscectomized joints were greater than the pressures of the paired intact joints by 70 and 42%, respectively. The mean medial compartment contact areas of the acute and chronic joints were lower than those of the intact joints by 60 and 50%, respectively; mean lateral compartment pressures remained the same. This study indicates that joint remodeling reduces joint contact pressures. It also suggests that the effectiveness of a treatment to reduce pressure concentrations may be determined only by comparison, at the same postoperative time, of the pressure with that of the chronically meniscectomized joint, since pressures decreased with time without treatment.