Effect of physical activity on functional performance and knee pain in patients with osteoarthritis : analysis with marginal structural models.
Mansournia MA, Danaei G, Forouzanfar MH, Mahmoodi M, Jamali M, Mansournia N, Mohammad K. Effect of physical activity on functional performance and knee pain in patients with osteoarthritis : analysis with marginal structural models. Epidemiology. 2012 Jul; 23(4):631-40.