Abstract
ObjectiveCurrent medical practice for the treatment of articular cartilage lesions remains a clinical challenge due to the limited self-repair ability of articular cartilage. Both experimental and clinical researches show that moderate exercise can improve articular cartilage repair process. However, optimal timing of moderate exercise is unclear. We aimed to evaluate the effect of timing of moderate treadmill exercise on repair of full-thickness defects of articular cartilage.DesignFull-thickness cartilage defects were drilled in the patellar groove of bilateral femoral condyles in a total of 40 male SD rats before they were randomly assigned into four even groups. In sedentary control (SED) group, no exercise was given; in 2-week (2W), 4-week (4W) and 8-week groups, moderate treadmill exercise was initiated respectively two, four and eight weeks after operation. Half of the animals were sacrificed at week 10 after operation and half at week 14 after operation. Femoral condyles were harvested for gross observation and histochemical measurement by O'Driscoll scoring system. Collagen type II was detected by immunohistochemistry and mRNA expressions of aggrecan and collagen type II cartilage by RT-PCR.ResultsBoth 10 and 14 weeks post-operation, the best results were observed in 4W group and the worst results appeared in 2W group. The histochemistry scores and the expressions of collagen type II and aggrecan were significantly higher in 4W group than that in other three groups (P<0.05).ConclusionsModerate exercise at a selected timing (approximately 4 weeks) after injury can significantly promote the healing of cartilage defects but may hamper the repair process if performed too early while delayed intervention by moderate exercise may reduce its benefits in repair of the defects.
Highlights
It is a great challenge for both orthopaedic surgeons and rehabilitation specialists to repair articular cartilage injuries or defects
Collagen type II was detected by immunohistochemistry and mRNA expressions of aggrecan and collagen type II cartilage by reverse transcription-polymerase chain reaction (RT-PCR). Both 10 and 14 weeks post-operation, the best results were observed in 4W group and the worst results appeared in 2W group
Moderate exercise at a selected timing after injury can significantly promote the healing of cartilage defects but may hamper the repair process if performed too early while delayed intervention by moderate exercise may reduce its benefits in repair of the defects
Summary
It is a great challenge for both orthopaedic surgeons and rehabilitation specialists to repair articular cartilage injuries or defects. Microenvironment plays an important role in maintenance and repair of articular cartilage.[3,4] Creating an environment which can facilitate the healing process and simultaneously avoid potentially deleterious forces acting to the repair site is advantageous for cartilage repair process. Compression and decompression forces during weight-bearing may nourish the articular cartilage.[6] It has been demonstrated that immobilization, even applied for a very short duration, exerts a harmful effect on healing articular cartilage [7,8,9]. Continuous passive motion has been reported to have beneficial effects due to the joint movement.[10,11] Palmoski et al, found that joint motion in the absence of normal loading did not maintain normal articular cartilage and joint loading was more important to the biological and functional properties of normal articular cartilage.[12]
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