Journal of Orthopaedic Research 12161-167 zyxwvutsrqponm The Journal zyxwvutsrqponm of Bone and Joint Surgery, Inc. zyxwvutsrqp 0 1994 Orthopaedic Research Society Articular Cartilage Thickness and Glycosaminoglycan Distribution in the Young Canine Knee Joint After Remobilization of the Immobilized Limb Ilkka Kiviranta, "Markku Tammi, *Jukka Jurvelin, *Jari Arokoski, zyx * Anna-Marja Saamanen, and "Heikki J. Helminen Department of Surgery, Kuopio University Hospital, and *Department of Anatomy, University of Kuopio, Kuopio, Finland Summary: The recovery of articular cartilage from atrophy induced by joint immobilization was investigated in immature dogs. In a previous study, we showed that 11 weeks of immo- bilization of the knee (stifle) joint of young dogs reduced the concentration of articular cartilage glycosaminoglycans (GAGs) by 13-47%. In the present study, right hindlimbs from six female beagles were immobilized for 11 weeks, as in the previous study, and then were remobilized for 15 weeks. Cartilage from the knee joint was compared with cartilage from nonimmobilized knees of eight age-matched control beagles. Histological samples taken from 11 different locations of the knee joint were stained with safranin 0, and micro- spectrophotometry was used to demonstrate distribution of GAGs in the tissue. After re- mobilization, GAG concentration was restored in the patellofemoral region and tibia1 condyles. On the summits of the femoral condyles, and especially at the periphery of the femoral condyles, GAG concentration remained 8-26% less than the control values. On the summits, the thickness of the uncalcified cartilage was as much as 15% less than in the age-matched controls. Consequently, the changes induced by unloading were reversible to a great extent, but a full restoration of articular cartilage was not obtained at all sites of the knee joint within the 15 weeks of remobilization. Immobilization of the skeletally immature joint therefore may affect the development of articular cartilage in such a way that very slow recovery or permanent alterations are induced. Cast immobilization of a limb often is a neces- sary part of orthopaedic treatment for both adults and children. Unfortunately, splinting of the joint decreases the amount of proteoglycans in articular cartilage and leads to degeneration of cartilage, as shown in experimental animals (1,3,16). In young, growing animals, immobilization also may affect the maturation of articular cartilage. In a previous study (lo), we found that cast immobilization of the knee joint of young, immature dogs for 11 weeks decreased the concentration of glycosaminoglycans Received R'ovember 28,1991; accepted July 2,1993. Address correspondence and reprint requests to Dr. I. Ki- viranta at Department of Surgery, Kuopio University Hospital, P.O. zyxwvutsrq Box 1777, SF-70211 Kuopio, Finland. (GAGs) in articular cartilage by 13-47%. The deple- tion of GAGs was most prominent near the joint surface; however, the cartilage surface remained in- tact, and the general histological structure did not reveal signs of osteoarthrosis. Changes in cartilage in the absence of fibrillation or ulceration have been reported to be reversible (18,21), although there also is evidence that the re- covery of the cartilage may be slow or incomplete (43). In this study, we duplicated our experiment involving 11 weeks of immobilization (10) with a new group of beagle dogs and then remobilized the joints for 15 weeks. The results of the previous ex- periment on immobilization gave us the data on the changes in cartilage that occur due to the cast immo- bilization. Samples from experimental and control zy 161