Proximal interphalangeal joint stiffness: Measurement and analysis

Purpose: The purpose of this study was to quantify the stiffness of the human finger proximal interphalangeal (PIP) joint and to study its relationship to different common clinical parameters. Methods: Eighty-nine normal adult subjects had their PIP joints of the index, middle, and ring fingers evaluated using a computer-controlled moment-angle plotter. This device was used to measure stiffness and energy absorbed at the PIP joint during passive flexion and extension. Results: The average overall stiffness was 0.05 N-cm/degree. There was a weak correlation between stiffness and energy absorbed and the size of the finger: they both increased with the size of the finger. The men's fingers were stiffer and absorbed more energy than the corresponding women's fingers. No significant associations were found between the time of day when the test took place, occupation, hobbies, or age with stiffness or absorbed energy. No significant differences were associated with hand dominance. The finger on the dominant hand had a larger circumference for both genders. Heavier individuals had more stiffness and absorbed more energy than lighter individuals. Conclusions: The PIP joint stiffness was defined quantitatively and measured over a wide cross-section of a normal population. This may allow future studies to record the outcome of different treatments for finger joint stiffness objectively. The stiffness was greater in men and in larger fingers.