The effects of joint immobilization on articular cartilage of the knee in previously exercised rats

Abstract

Studies have determined the effects of joint immobilization on the articular cartilage of sedentary animals, but we are not aware of any studies reporting the effects of joint immobilization in previously trained animals. The objective of the present study was to determine whether exercise could prevent degeneration of the articular cartilage that accompanies joint immobilization. We used light microscopy to study the thickness, cell density, nuclear size, and collagen density of articular cartilage of the femoral condyle of Wistar rats subjected to aerobic physical activity on an adapted treadmill five times per week. Four groups of Wistar rats were used: a control group (C), an immobilized group (I), an exercised group (E), and an exercised and then immobilized group (EI). The right knee joints from rats in groups I and EI were immobilized at 90°C of flexion using a plastic cast for 8 weeks. Cartilage thickness decreased significantly in group I (mean, 120.14 AE 15.6 lm, P < 0.05), but not in group EI (mean, 174 AE 2.25), and increased significantly in group E (mean, 289.49 AE 9.15) compared with group C (mean, 239.20 AE 6.25). The same results were obtained for cell density, nuclear size, and collagen density (in all cases, P < 0.05). We concluded that exercise can prevent degenerative changes in femoral articular cartilage caused by immobilization of the knee joint.

The benefits and limitations of animal models for translational research in cartilage repair

“…Post-operative rehabilitation of cartilage repair in humans varies from centre to centre, it has been shown free movement and gradual increase in weight bearing improves outcomes, however, this is complex to ensure in animal models (Nishino et al 2010 ; Assche et al 2011 ). When using an in vivo model casts can be used to immobilise rat limbs (Kojima et al 2014 ; Maldonado et al 2013 ), however it is more common in large animals such as goats and sheep to keep them in small pens in the immediate post-operative period (Marmotti et al 2013 ) to limit their mobilising. In some animals, such as horses, non-weight bearing is impossible, and can cause severe life-threatening illnesses.…”

Impact of a daily exercise dose on knee joint cartilage – a systematic review and meta-analysis of randomized controlled trials in healthy animals

“…Studies of a low daily dose of exercise reported decreased 14,43 or no effect 14,46,47 or increased 43 cartilage thickness. Studies of a moderate exercise dose reported no effect 50,52,53 or increased cartilage thickness 18,19,51 , while studies of a high daily dose of exercise reported no effect 16,34e36 or decreased 34,37,39,40,49,54 cartilage thickness.…”

“…Rodents (mean age (±SD) in weeks 35 ± 32) were male Wistar rats in six studies 14,37,43,47,48,51 , female SpragueeDawley rats in two 45,46 female Guinea-pigs in one and female Golden hamsters in one 34,38 . Rabbits (mean age (±SD) in weeks 39 ± 8) were New Zealand white rabbits in all the studies.…”

Análise termogravimétrica da cartilagem articular de ratos exercitados após imobilização

“…Além disso, ele promove aumento do volume da cartilagem e adaptação da mesma ao esforço 20 e estimulando os condrócitos a produzir os elementos que compõem a matriz extracelular 13,21,22 . Del Carlo et al 23 realizaram um estudo com ratos imobilizados por 45 dias e remobilizados livre e por meio de exercício físico, no qual os animais que realizaram natação demonstraram quadro menos severo de lesão no tecido cartilaginoso, demonstrada por análise histológi-ca.…”