Measurement of Joint Stiffness in the Hand: A Preliminary Investigation of the Reliability and Validity of Torque Angle Curves

Abstract

The principal aim of this study was to examine aspects of the reliability and validity of the Torque Angle Curve (TAC) technique as a measure of joint stiffness. Specifically, inter-rater and intra-rater reliability were examined as well as the percent agreement of therapist evaluation of joint ‘end feel’ (i.e. springy or non-springy). Convergent validity of the TAC technique was studied by assessing the extent of agreement between TAC scores and therapist ratings of end feel. Thirty-eight joints were assessed in 24 subjects. Inter-rater reliability ICC (2,2) of the TAC technique was .80 and intra-rater reliability ICC (3,1) was .76 for rater A and ICC (3,1) .64 for rater B. Percent agreement for the end-feel technique was 68.4% with Kappa = .42. A significant difference was found between TAC scores for springy joints (mean [SD] 12.0° [3.7]) and TAC scores for non-springy joints (mean [SD] 7.2° [2.8]), when raters agreed on end feel (p = .000). When raters did not agree on end feel, the mean TAC score was 9.6° [2.2]. Results from this preliminary investigation suggest that the TAC technique provides a more reliable estimate of joint stiffness than the use of end feel. Further research with a larger sample size is required to replicate findings.