Comparisons of weight-bearing and non-weight-bearing tests of knee proprioception performed by patients with patello-femoral pain syndrome and asymptomatic individuals

Objective: To compare non-weight-bearing (sitting) and weight-bearing (standing, with similar to 95% of body weight on the test leg) tests of knee proprioception performed by patients with patello-femoral pain syndrome (PFPS) and asymptomatic individuals. Design: A repeated measures design, repeated on two occasions. Setting: Athletic injuries clinic. Participants: Seven men and 17 women with PFPS, and age- and sex-matched asymptomatic individuals. Interventions: With their eyes closed, subjects extended their knee in sitting, or flexed their knees in standing, attempting to replicate target angles (15 degrees, 30 degrees, 45 degrees, and 60 degrees knee flexion) measured using an electrogoniometer. Main outcome measure: Observed angle of knee flexion during joint angle replication tests. Results: Test-retest reliability coefficients (0.17-0.79) and between-session measurement error (+/-2.0 degrees to +/-6.4 degrees) varied widely. There was a tendency for reliability coefficients to be greater and between-session measurement error to be lower, for PFPS subjects, and for sitting tests. No significant differences were observed between the scores of the PFPS and asymptomatic subjects, at any of the four target knee angles. Conclusions: Scores in sitting should not be compared with those in standing. Clinically, the low reliability coefficients, large between-session measurement error, and finding of no statistically significant difference between PFPS and asymptomatic subjects suggest that the diagnostic value of the proprioceptive tests used is questionable. Further research is required to develop more precise tests of knee proprioception and to determine if the present results are applicable to other pathologies.