Effects of compressive loading on articular cartilage repair of knee joint in rats.

Effects of compressive loading on articular cartilage repair was studied. Thirty adolescent Long-Evans rats were used as experiment animals. A full-thickness defect of cartilage was created by drilling with a k-wire, 1.2 mm in diameter, into the weight bearing area of medial femoral condyle of each of bilateral knee joints. Free movement was permitted postoperatively. One leg of each rat received normal weight bearing on knee joint as experiment leg. The contralateral leg was used as the control. The control legs were paw resected to avoid weight bearing on joint cartilages but this did not interfere with the motion of knee joints. The articular cartilage repair was estimated by macroscopic examination and microscopic examination 6 weeks after surgery. Scoring systems were used to evaluate the quantity of repaired tissue in macroscopic examination and the quality of repaired tissue in microscopic examination. The differences of articular cartilage repair affected by compressive loading was analyzed statistically by paired t-test. We concluded that the effects of compressive loading on cartilage repair was to accelerate the metaplasia of repair tissue into hyaline cartilage but not to increase the quantity of repaired tissue.