Background: Hallux rigidus is a common problem characterized by localized osteoarthritis and limited range of motion of the hallux. First metatarsophalangeal joint arthrodesis has been the accepted procedure for the treatment of late-stage disease. Despite the success of arthrodesis, some patients object to the notion of eliminating motion at the metatarsophalangeal joint. For this reason, motion-sparing procedures such as the modified oblique Keller capsular interpositional arthroplasty have been developed. Methods: We compared a cohort of ten patients (ten toes) who had undergone the modified Keller arthroplasty with a group of twelve patients (twelve toes) who had undergone a first metatarsophalangeal joint arthrodesis at an average of sixty-three and sixty-eight months, respectively. Clinical outcomes were evaluated, and range of motion, great toe dynamometer strength, plantar pressures, and radiographs were assessed. Results: Clinical outcome differences existed between the groups, with the American Orthopaedic Foot and Ankle Society score being significantly higher for the arthroplasty group than for the arthrodesis group. The arthroplasty group had a mean of 54° of passive and 30° of active range ofmotion of the first metatarsophalangeal joint. The plantar pressure data revealed significantly higher pressures in the arthrodesis group under the great toe but not under the second metatarsal head. Conclusions: The modified oblique Keller capsular interpositional arthroplasty appears to be a motion-sparing procedure with clinical outcomes equivalent to those of arthrodesis, and it is associated with a more normal pattern of plantar pressures during walking. Level of Evidence: Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.