The authors evaluated the effect of modified Root orthoses on first metatarsophalangeal joint extension. Motion within the joint was measured dynamically following the insertion of bone markers into the first metatarsal and the hallux. Extension at the joint was greatest when the subjects were barefoot, the mean angle being 62 degrees. Plimsolls restricted extension of the joint to a mean angle of 57 degrees, while orthoses further reduced the angle of metatarsophalangeal joint extension to a mean angle of 55 degrees. The marginal reduction in first metatarsophalangeal joint extension caused by functional orthoses may be of therapeutic value in the early stages of hallux rigidus, when restricting motion at the joint may slow or prevent development of subchondral sclerosis.