Effects of hallux limitus on plantar foot pressure and foot kinematics during walking.

The effects of hallux limitus on plantar foot pressure and foot kinematics have received limited attention in the literature. Therefore, a study was conducted to assess the effects of limited first metatarsophalangeal joint mobility on plantar foot pressure. It was equally important to identify detection criteria based on plantar pressures and metatarsophalangeal joint kinematics, enabling differentiation between subjects affected by hallux limitus and people with normal hallux function. To further our understanding of the relation between midtarsal collapse and hallux limitus, kinematic variables relating to midtarsal pronation were also included in the study. Two populations of 19 subjects each, one with hallux limitus and the other free of functional abnormalities, were asked to walk at their preferred speed while plantar foot pressures were recorded along with three-dimensional foot kinematics. The presence of hallux limitus, structural or functional, caused peak plantar pressure under the hallux to build up significantly more and at a faster rate than under the first metatarsal head. Additional discriminators for hallux limitus were peak dorsiflexion of the first metatarsophalangeal joint, time to this peak value, peak pressure ratios of the first metatarsal head and the more lateral metatarsal heads, and time to maximal pressure under the fourth and fifth metatarsal heads. Finally, in approximately 20% of the subjects, with and without hallux limitus, midtarsal pronation occurred after heel lift, validating the claim that retrograde midtarsal pronation does occur.