Objective:To differentitate the myogenic from arthrogenic component of knee contracture resulting from being immobilized in extension for 4 weeks. Method:Ten rabbits were used as experimental animals. The right hindlimbs were immobilized with knee in extension for 4 weeks, while the left severed as controls. The range of motion ( ROM ) of both knees were measured before and after myotomy. Result:In immobilized and control hindlimbs, the mean ROM of the knee were 79.5°and 138.5°, respectively. The gain of ROM after myotomy in immobilized and control hindlimbs were 8.7° ±0. 45°, 11.6° +0.58°, respectively. Only 14.75% of the limitation of motion in ROM were accounted for by the myotomy component. Conclusion:After immobilizing for 4 weeks, the ROM of knee was significantly limited. However, the myogenic part was small and not different from normals.