Determinants of self-report outcome measures in people with knee osteoarthritis.
OBJECTIVE
To identify the determinants of self-report mobility measures in people with knee osteoarthritis (OA) and to compare self-report measures with physical performance.


METHODS
Cross-sectional, prospective.


METHODS
Motor performance laboratory and human mobility research center.


METHODS
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.


METHODS
Not applicable.


METHODS
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 standardized 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.
Maly
Monica R
MR
School of Physical Therapy, University of Western Ontario, London, ON, Canada.
Costigan
Patrick A
PA
Olney
Sandra J
SJ
D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000534:rehabilitation*; D010147:Pain Measurement; D010358:Patient Participation; D011336:Probability; D011446:Prospective Studies; D011788:Quality of Life; D016059:Range of Motion, Articular / Q000502:physiology*; D012649:Self Concept; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D018434:Sickness Impact Profile