Longitudinal analysis of cartilage atrophy in the knees of patients with spinal cord injury

Objective A previous cross‐sectional study indicated that the morphology of patellar and tibial cartilage is subject to change after spinal cord injury (SCI). The aim of this study was to perform a longitudinal analysis of cartilage atrophy in all knee compartments, including the femoral condyles, in SCI patients over 12 months. Methods The right knees of 9 patients with complete, traumatic SCI were examined shortly after the injury (mean ± SD 9 ± 4 weeks) and at 6 and 12 months postinjury. Three‐dimensional morphology of the patellar, tibial, and femoral cartilage (mean and maximum thickness, volume, and surface area) was determined from coronal and transversal magnetic resonance images (fat‐suppressed gradient‐echo sequences) using validated postprocessing techniques. Results The mean thickness of knee joint cartilage decreased significantly during the first 6 months after injury (range 5–7%; P < 0.05). The mean change at 12 months was 9% in the patella, 11% in the medial tibia, 11% in the medial femoral condyle, 13% in the lateral tibia, and 10% in the lateral femoral condyle (P < 0.05 for all compartments). Conclusion This is the first report of a longitudinal analysis of cartilage atrophy in patients with SCI. These data show that human cartilage atrophies in the absence of normal joint loading and movement after SCI, with a rate of change that is higher than that observed in osteoarthritis (OA). A potential clinical implication is that cartilage thinning after SCI may affect the stress distribution in the joint and render it vulnerable to OA. Future studies should focus on whether specific exercise protocols and rehabilitation programs can prevent cartilage thinning.