A hand dynamometer connected to a smartphone could be used by patients with rheumatoid arthritis (RA) to self-assess disease activity, the results of a new study suggest. This approach was assessed in 82 patients with RA. Three types of handgrip strength — power, pinch and tripod — were tested and captured by an interactive mobile application. The three measures of grip strength at baseline were negatively correlated with the DAS28 score of RA disease activity. Power grip strength was negatively correlated with the DAS28 score in a longitudinal analysis of 32 patients. An independent correlation of power grip strength with male sex was also found, whereas this measure was inversely correlated with disease duration, patient global assessment and levels of C-reactive protein.