The purpose of this study was to determine whether differences in sensation, ankle dorsiflexion (DF), and subtalar joint (STJ) motion exist between 1) diabetic patients with a history of plantar ulcer (DMW Group), 2) diabetic patients without a history of plantar ulcer (DMWO Group), and 3) a nondiabetic control group (NDC Group). There were 23, 23, and 24 subjects in the respective groups. The mean age for each group was 58, 63, and 60 years, respectively. The mean DF for each group was 2, 5, and 7 degrees, respectively, and the mean STJ motion was 26, 31, and 35 degrees, respectively. Mode values for sensation with Semmes-Weinstein monofilaments were 6.10, 5.07, and 4.17. The results indicate the DMW Group had significantly less sensation, DF, and STJ motion than the NDC Group (p less than .05). In the DWM Group, the ulceration was seen more often on the side with least motion. Limited DF and STJ motion may restrict the foot's ability to absorb shock and transverse rotation, contributing to the pathogenesis of plantar ulceration in the insensitive foot. Although these results demonstrate an association, not a causative relationship, we believe diabetic patients should be screened routinely for insensitivity and limited joint mobility at the feet and appropriate preventive measures should be taken.