Redistribution of joint moments is associated with changed plantar pressure in diabetic polyneuropathy

ABSTRACT: BACKGROUND: Patients with diabetic polyneuropathy (DPN) are often confronted with ulceration of foot soles. Increased plantar pressure under the forefoot has been identified as a major risk factor for ulceration. This study sets out to test the hypothesis that changes in gait characteristics induced by DPN related muscle weakness are the origin of the elevated plantar pressures. METHODS: Three groups of subjects participated: people diagnosed with diabetes without polyneuropathy (DC), people diagnosed with diabetic polyneuropathy (DPN) and healthy, age-matched controls (HC). In all subjects isometric strength of plantar and dorsal flexors was assessed. Moreover, joint moments at ankle, knee and hip joints were determined while walking barefoot at a velocity of 1.4 m/s. Simultaneously plantar pressure patterns were measured. RESULTS: Body-mass normalized strength of dorsal flexors was significantly reduced in people with diabetes, both DC and DPN, compared to HC-subjects. Compared to HC and DC-subjects, DPN-participants walked with a reduced internal knee extensor moment and an increased internal plantar flexor moment at the first half of the stance phase. Moreover, in DPN-subjects the ratio of forefoot-to-rear foot plantar pressures was increased. CONCLUSIONS: The results of this study suggest that adverse plantar pressure patterns are associated with redistribution of joint moments. The reduced lower leg muscle strength alone did not sufficiently explain this redistribution of joint moments and affected plantar pressure patterns.