In knee OA , strong evidence was found that avoidance of activities is associated with activity limitations via muscle weakness ( mediation by muscle weakness ) , strong evidence was found for an association between muscle weakness and activity limitations , and weak evidence was found that pain and psychological distress are associated with muscle weakness via avoidance of activities ( mediation by avoidance ) .
In hip OA , weak evidence was found for mediation by muscle weakness ; and strong evidence was found for an association between muscle weakness and activity limitations .
The avoidance model in patients with knee and hip osteoarthritis ( OA ) hypothesizes that pain and psychological distress lead to avoidance of activities , and thereby to muscle weakness and activity limitations .
This paper systematic ally review s the scientific evidence for the validity of this avoidance model .
The efficacy of home based progressive strength training in older adults with knee osteoarthritis: a randomized controlled trial.
OBJECTIVE To test the effects of a high intensity home-based progressive strength training program on the clinical signs and symptoms of osteoarthritis ( OA ) of the knee . METHODS Forty-six community dwelling patients , aged 55 years or older with knee pain and radiographic evidence of knee OA , were r and omized to a 4 month home based progressive strength training program or a nutrition education program ( attention control ) .  Thirty-eight patients completed the trial with an adherence of 84 % to the intervention and 65 % to the attention control . The primary outcome was the Western Ontario and McMaster Universities Osteoarthritis ( WOMAC ) index pain and physical function subscales . Secondary outcomes included clinical knee examination , muscle strength , physical performance measures , and question naires to measure quality of life variables . RESULTS Patients in the strength training group who completed the trial had a 71 % improvement in knee extension strength in the leg reported as most painful versus a 3 % improvement in the control group ( p < 0.01 ) . In a modified intent to treat analysis , self-reported pain improved by 36 % and physical function by 38 % in the strength training group versus 11 and 21 % , respectively , in the control group ( p = 0.01 for between group comparison ) . In addition , those patients in the strength training group who completed the trial had a 43 % mean reduction in pain ( p = 0.01 vs controls ) , a 44 % mean improvement in self-reported physical function ( p < 0.01 vs controls ) , and improvements in physical performance , quality of life , and self-efficacy when compared to the control group . CONCLUSION High intensity , home based strength training can produce substantial improvements in strength , pain , physical function and quality of life in patients with knee OA
In knee OA , strong evidence was found that avoidance of activities is associated with activity limitations via muscle weakness ( mediation by muscle weakness ) , strong evidence was found for an association between muscle weakness and activity limitations , and weak evidence was found that pain and psychological distress are associated with muscle weakness via avoidance of activities ( mediation by avoidance ) .
In hip OA , weak evidence was found for mediation by muscle weakness ; and strong evidence was found for an association between muscle weakness and activity limitations .
The avoidance model in patients with knee and hip osteoarthritis ( OA ) hypothesizes that pain and psychological distress lead to avoidance of activities , and thereby to muscle weakness and activity limitations .
This paper systematic ally review s the scientific evidence for the validity of this avoidance model .