Activity limitations (walking, stair-climbing) are common with knee osteoarthritis (OA).
Causal factor (hypothesize): muscle weakness (evidence is limited).
In cross-sectional studies:
- The association : muscle strength & activity limitations.
- Baseline muscle strength is a predictor of activity limitations.
- Limitations : Association of a decrease in muscle & an increase in activity ?
This longitudinal association has been studied :
- Observational studies : Conflict results
- A clinical trial : failure to control for confounding variables