Isometric Quadriceps Strength in Women with Mild, Moderate, and Severe Knee Osteoarthritis

Palmieri-Smith RM, Thomas AC, Karvonen-Gutierrez C, Sowers MF: Isometric quadriceps strength in women with mild, moderate, and severe knee osteoarthritis. Am J Phys Med Rehabil 2010; 89: 541-548. Objective: Quadriceps weakness is a common clinical sign in persons with moderate-to-severe osteoarthritis and results in physical disability; however, minimal data exist to establish whether quadriceps weakness is present in early stages of the disease. Therefore, our purpose was to determine whether quadriceps weakness was present in persons with early radiographic and cartilaginous evidence of osteoarthritis. Further, we sought to determine whether quadriceps strength decreases as osteoarthritis severity increases. Design: Three hundred forty-eight women completed radiologic and magnetic resonance imaging evaluation, in addition to strength testing. Anterior-posterior radiographs were graded for tibiofemoral osteoarthritis severity using the Kellgren-Lawrence scale. Scans from magnetic resonance imaging were used to assess medial tibiofemoral and patellar cartilage based on a modification of the Noyes scale. The peak knee extension torque recorded was used to represent strength. Results: Quadriceps strength (Nm/kg) was 22% greater in women without radiographic osteoarthritis than in women with osteoarthritis (P < 0.05). Quadriceps strength was also greater in women with Noyes' medial tibial and femoral cartilage scores of 0 when compared in women with Noyes' grades 2 and 3-5 (P <= 0.05). Conclusions: Women with early evidence of osteoarthritis had less quadriceps strength than women without osteoarthritis as defined by imaging.