Severity of hand osteoarthritis and its association with upper extremity impairment in a population of disabled older women: the Women's Health and Aging Study.

Most severity indices of osteoarthritis (OA) include measures of physical function which render them unsuitable for assessing the impact of OA on disability. Data from 1002 moderate to severely disabled community-dwelling women > or = 65 years were used to develop hand OA severity indices which are independent of functional status. Baseline exams and strength tests were conducted by trained nurse examiners. Each distal and proximal interphalangeal joint, and first carpometacarpal joint (20 joints in all) was scored for the presence of a) bony enlargement or deformity, and b) pain on motion or tenderness on palpation. Severity indices were then created: Deformity index (DEF) = sum of joints with bony changes (0-20); Pain/Tenderness index (PT) = sum of joints with pain or tenderness (0-20); and Combined Deformity/Pain index = sum of DEF and PT (0-40). These indices were then validated against grip and pinch strength. All three indices showed a significant trend for weaker grip strength as severity index scores increased. When the 25th, 50th and 75th percentiles were used to divide each severity index into levels of involvement, a threshold effect was observed with significantly poorer grip strength performance above the 75th percentile for each index. Similar results were seen for pinch strength. In conclusion, these hand OA severity indices, based on examination findings alone, help distinguish disease status, and may provide a valuable research tool for investigating the role of hand OA in impairment and disability.