Exercise as Osteoarthritis Treatment in Wistar Rats Promotes Frequency-Dependent Benefits

This study investigated the effects of different frequencies of moderate treadmill exercise on a knee osteoarthritis (OA) model in Wistar rats. Sixty male Wistar rats were randomly assigned to four groups: Sham, OA, OA + exercise three times/week (OA + 3×), and OA + exercise five times/week (OA + 5×). OA was induced via intra-articular injection of sodium monoiodoacetate (MIA) in the right knee. Fifteen days post-MIA, exercise treatment began with a one-week adaptation period, followed by eight weeks of aerobic training. Protocols involved treadmill walking (30 min/day) at 13 m/min for the first four weeks and 16 m/min for the last four weeks. At the end, animals were anesthetized and euthanized for collection of intra-articular tissues and gastrocnemius muscle. Both exercise regimens inhibited OA progression; however, OA + 5× yielded more pronounced effects, including greater energy expenditure, weight reduction, oxidative stress modulation, decreased pro-inflammatory and catabolic markers, increased anti-inflammatory and anabolic parameters, reduced injury scores, prevention of cartilage thinning, and increased cartilage surface area. Although both frequencies conferred cartilage protection, moderate exercise five times per week produced superior therapeutic outcomes, suggesting a dose-dependent benefit of exercise in OA management.