Rheumatoid arthritis: a two-axis goniometer to measure metacarpophalangeal laxity.

A 2-axis goniometer has been developed which accommodates the metacarpophalangeal (MCP) changes of rheumatoid arthritis and permits accurate measurement of laxity of the MCP joints. Measurements made with the instrument on 51 subjects with definite or classical rheumatoid arthritis showed high percentages of intrarater and interrater agreement for repeated trials. These results suggest that, following the methods outlined, the 2-axis goniometer can be used to obtain reliable objective measurements of MCP lateral mobility by 1 or more raters with a minimum of training.