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 .
Determinants of self-report outcome measures in people with knee osteoarthritis.
OBJECTIVES To identify the determinants of self-report mobility measures in people with knee osteoarthritis ( OA ) and to compare self-report measures with physical performance . DESIGN Cross-sectional , prospect i ve . SETTING Motor performance laboratory and human mobility research center . PARTICIPANTS A convenient sample of 54 participants with medial compartment knee OA ( 32 women , 22 men ; age 68.3+/-8.7y ; range , 50 - 87y ) . Three participants were excluded because of the presence of lateral knee OA on radiographs . INTERVENTIONS Not applicable . MAIN OUTCOME MEASURES Self-reports were recorded by using the Western Ontario McMaster Universities Osteoarthritis Index ( WOMAC ) and the Medical Outcomes Study 36-Item Short-Form Health Survey ( SF-36 ) . Performance measures included the  six-minute walk test ( 6MWT ) , Timed Up & Go ( TUG ) test , and a st and ardized stair-climbing task ( STR ) . RESULTS Stepwise linear regression analysis identified models that included pain , quadriceps and hamstrings strength , and depression to explain 62 % to 73 % of the variance in scores on the physical functioning subscale of the WOMAC and the SF-36 . These self-report measures had a moderate relation ( r range , .46-.64 ) with performance measures ( 6MWT , TUG , STR ) . CONCLUSIONS Self-report measures were strongly related to pain ; physical performance measures were strongly related to self-efficacy . Regression models showed that self-report scores reflect pain , knee strength , and depression . The relation between self-report and performance measures was moderate , suggesting that these examine different aspects of mobility
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 .