Passive ankle stiffness in subjects with diabetes and peripheral neuropathy versus an age-matched comparison group

Background and Purpose. Patients with diabetes mellitus and peripheral neur opathy (DM and PN) often complain of joint stiffness. Although stiffness ma r contribute to some of the impairments and functional limitations found in these patients, it has not been quantified in this population. The purpose of this study was to quantify and compare passive ankle stiffness and dors iflexion (DF) range of motion in subjects with DM and PN versus an age-matc hed comparison group. Subjects. Thirty-four subjects were tested (17 subjec ts with DM and PN and 17 subjects in an age-matched comparison group). Ther e were 10 male subjects and 7 female subjects in each group. Methods. A Kin -Com dynamometer was used to measure passive plantar flexor torque as each subject's ankle was moved from plantar flexion into dorsiflexion at 60 degr ees/s. The following variables were compared using a Student t test: initia l angle (angle of onset of plantar flexor torque), maximal dorsiflexion ang le, plantar flexor muscle excursion (difference between initial angle and m aximal dorsiflexion angle), slope of the first half of the plantar flexor t orque curve (stiffness 1 measurement), and slope of the second half of the plantar flexor torque curve (stiffness 2 measurement). Results. The subject s with DM and PN group had smaller maximal dorsiflexion angles and less pla ntar flexor muscle excursion than the comparison group. There was no differ ence in initial angle, stiffness 1 measurement, or stiffness 2 measurement. Conclusion and Discussion. Although the subjects with DM and PN had less d orsiflexion range of motion than did the comparison group, there was no dif ference in stiffness between the groups. This finding suggests that people with DM and PN have "short" versus "stiff" plantar flexor muscles.