Objective: In knees, quadriceps strength may protect against osteoarthritis (OA). Muscle activity is a major determinant of forces at the hand joints, and grip is a common task during which high muscle forces are sustained, especially at the proximal hand joints (metacarpophalangeal [MCP] joints and thumb base). This longitudinal study of radiographic hand OA examined the association between incident OA at different hand joints and maximal grip strength.
Methods: Four hand joint groups were studied: distal interphalangeal (DIP), proximal interphalangeal (PIP), MCP, and the base of the thumb (carpometacarpal and scaphotrapezial combined). Subjects were members of the Framingham OA Study who had a baseline radiograph in 1967-1969 and a followup radiograph in 1992-1993 (mean followup 24 years) and had no prevalent radiographic OA in any hand joint at baseline. Incident disease was defined as development of OA defined as a modified Kellgren/Lawrence grade of > or =2. Grip strength was measured in kilograms by dynamometer in 1958-1961 and again in 1960-1963, and the 2 measures were averaged and divided into sex-specific tertiles. Joint-based analysis was performed by adjusting for age, physical activity, and occupational category using the lowest grip strength tertile as the referent.
Results: Baseline and followup radiographs were obtained from 746 subjects. Of these, 453 subjects with no prevalent OA at baseline were eligible for analysis. In men, higher maximal grip strength was associated with an increased risk of OA in the PIP (highest tertile odds ratio [OR] 2.8 compared with lowest tertile, 95% confidence interval [95% CI] 1.2-6.7), MCP (highest tertile OR 2.9, 95% CI 1.1-7.4), and thumb base joints (highest tertile OR 2.8, 95% CI 1.1-7.4). In women, there was increased risk of OA in the MCP joints (highest tertile OR 2.7, 95% CI 1.1-6.4).
Conclusion: Men with high maximal grip strength are at increased risk for the development of OA in the PIP, MCP, and thumb base joints, and women, in the MCP joints. No association was found between maximal grip strength and incident OA in the DIP joints of men or women.