Quadriceps strengthening exercises may not change pain and function in knee osteoarthritis

It is believed that Quadriceps strength training may reduce pain and improve functional activity in patients with knee osteoarthritis (OA). This improvement is generally attributed to an increase in quadriceps strength. This study investigated whether quadriceps muscle strength increases with decreasing pain, improving functional activity in knee OA. Twenty-four patients with knee OA participated in an 8-week treatment protocol including traditional physical therapy and strength training 3 sessions per week. Measurements were conducted before and after the intervention and included the peak torque of quadriceps muscle, pain by visual analogue scale (VAS), short Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and functional activity by the 2 minute walking test (2MWT) and time up & go test (TUGT). After the intervention, analysis of data illustrated that changes in quadriceps muscle strength correlated with changes in VAS (r2 = 0.310, p = 0.005), WOMAC (r2 < 0.278, p < 0.008) and 2MWT (r2 < 0.275, p < 0.009) significantly, although the correlation slope was negligible. No correlation was found between muscle strength and TUGT. However, the strength training significantly improved quadriceps muscle strength (p = 0.013), pain and functional activity (p = 0.000). This study showed that reduction in pain and improvement in functional activity occurs independently from an increase in quadriceps muscle strength in knee OA. It seems that increased quadriceps muscle strength may not be a cause of improvement in pain and functional activity in knee OA.