Knee ligament injury occurs frequently during athletic activities particularly for women and knee orthoses are often involved in post-injury management. A lightweight and aesthetically more acceptable Dynamic Knee Orthosis System (DKOS) is presented to females with a knee ligament injury (anterior cruciate ligament injury for example). The DKOS is embodied as a pair of close-fitting leggings with a detachable dynamic belt on the waist. DKOS can be used 1) to provide support for injured knee joint with lighter physical burden, 2) to restrict range of motion if needed, and 3) to assist regaining range of motion in post-surgical rehabilitation process. Statistical analysis of a series of biomechanical tests suggested that the proposed orthosis had less constraint on quadriceps muscles yet was less supportive than the commercial brace during running, triple hop and drop landing tasks. Subjective evaluation shows that 10 uninjured participants felt the proposed orthosis was more comfortable yet had same support as a commercial brace.