The Relation Between Upper Extremity Joint Involvement and Grip Force in Early Rheumatoid Arthritis: a Retrospective Study

To investigate the relation between joint involvement in the upper extremities and grip force in patients with early rheumatoid arthritis (RA). An inception cohort of 225 patients with early RA was followed according to a structured protocol. The same rheumatologist assessed all patients for swollen joints and joint tenderness. Grip force was measured (Grippit; AB Detektor, Gothenburg, Sweden) at the same visit. Average grip force values for the dominant hand were expressed as % of expected, based on age- and sex-specific reference values from the literature. Associations between grip force and current synovitis or tenderness of individual joints, and other disease parameters measured at the same visit, were examined. Patients with current synovitis of the wrist joint or ≥ 1 metacarpophalangeal (MCP) joint of the dominant hand had a significantly lower grip force at inclusion, at 1 year and at 5 years. Proximal interphalangeal joint tenderness and MCP joint tenderness were consistently associated with reduced grip force. In multivariate analysis, extensive MCP joint synovitis was associated with lower grip force at inclusion (β - 2.8% per joint; 95% CI - 5.3 to - 0.4), and also at the 1-year follow-up. Patient reported pain scores and erythrocyte sedimentation rates had independent negative associations with grip force at all time points. In patients with early RA, extensive synovitis of the MCP joints was associated with reduced grip force, independently of other upper extremity joint involvement. Pain and inflammation have effects on hand function beyond those mediated by local synovitis.