Background and purpose: Pain during activities of daily living is a common presenting complaint of individuals with knee osteoarthritis and anterior cruciate ligament injury. Knee pain is also associated with a decrease in quality of life for people with osteoarthritis. The purpose of the present study was to examine the dose-response relationship between knee joint forces and painful symptoms, and whether the acute symptoms, were associated with individuals' quality of life.
Method: This was a cross-sectional cohort correlation study. Seventeen individuals with anterior cruciate ligament (ACL)-deficient knees diagnosed with ipsilateral knee osteoarthritis completed the ACL quality of life questionnaire (ACL-QOL). The subjects also rated pain associated with each of five incremental isometric knee extension tests, proportional to their body weight. Analysis of variance was used to assess the association between pain and normalized torque. Linear regression was used to assess the correlation between the ACL-QOL score and the total pain experienced during the graded test.
Results: A strong relationship was found between the level of perceived knee pain and the amount of isometric torque produced (Pearson's r = 0.98; p < 0.001). There was a statistically significant relationship between pain during the graded isometric test and the ACL-QOL (Pearson's r = -0.56; p = 0.016).
Conclusions: Since knee joint compression is a function of active isometric knee extension torque, increased painful symptoms were associated with increased compression forces at the knee joint for these subjects. The relationship between pain provocation and disease-specific quality of life provides evidence for the proposed joint provocation test for this subject population. Weakness caused by osteoathritis (OA) may, in part, be a negative conditioning response that would need to be overcome in rehabilitation.