The morphology and composition of healthy mature articular cartilage is optimized to its primary function of load transfer and distribution. In the osteoarthritic state however, homeostasis of the knee joint is significantly altered, such that as the load is placed on the joint there is a progressive worsening of cartilage damage over time. Altered joint mechanics and intra-articular biological processes are thought to play pivotal roles in the initial breakdown and potentiation of cartilage damage which is the hallmark finding in knee OA leading to knee pain. Aquatic therapy alleviates stress on joints and provides people with pain or arthritis a safe opportunity to engage in activity. Walking or running with weight support on a lower-body positive-pressure (LBPP) treadmill similar to aquatic exercise therapy is a novel training and rehabilitation modality for individuals with lower extremity pathologies due to its ability to limit pain. This treadmill provides a controlled off-loading of the lower extremities with significant benefit being shown after 12 weeks of training in overweight individuals with knee OA on knee pain, function and muscle strength. Although these methodologies (LBPP treadmill and aquatic therapy) alter the joint mechanics, the intra-articular biological effect on joint disease remains unknown.
Diminished muscle strength is a common symptom associated with onset of knee osteoarthritis. Quadriceps muscle impairment in patients with knee OA is well documented in the literature. Muscle impairments in patients with OA are not limited to quadriceps but also involve hamstrings. Muscle strength, especially quadriceps, is a major determinant of both performance-based and self-reported physical function in subjects with knee OA. The evidence supports the benefit of exercise therapy (both land and aquatic), including global and targeted resistance training, in reducing pain and improving function in subjects with knee OA however research to date has been unable to quantify the disease-modifying effect of any form of exercise.
A recent study from investigators laboratory in individuals with knee OA, walking at self-selected speed, found that at a single session of 45 minutes of 50% body weight (BW) walking on this treadmill leads to a significant decrease in knee joint pain, and reduced pathologic gait features. It also decreased the serum concentration of biomarkers of inflammation (IL-6 and IL-8), adipokines and cartilage tissue turnover (cartilage oligomeric matrix protein, COMP)24 compared to 100% full body weight walking. The benefits of both types of exercise are primarily as a result of the decreased effects of gravity with buoyancy or positive pressure being associated with decreased compressive and shear joint forces at the knee.25 To investigators’ knowledge no prior study has performed a longitudinal clinical trial of either treatment in sedentary older individuals as a treatment for concurrent knee OA and CVD. The longitudinal use of such a treadmill may allow these individuals to safely engage in physical activity, reducing joint pain, improving function, and improving cardiovascular parameters. The present pilot study will establish the conditions and parameters for a future longer-term clinical trial that aims to compare of impacts of aquatic therapy exercise program and lower body positive pressure treadmill walking on biological markers of joint disease, joint kinematics and thigh muscle strength in individuals with knee pathology.
The study investigators propose is a randomized controlled trial in individuals with mild to moderate knee OA (n=15 in each group), evaluating the symptomatic, biochemical, and biomechanical benefits of 3 walking exercise treatments: 1) LBPP treadmill walking 2) aquatic walking 3) standard of care land-based or community walking exercise for the same duration.
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