On the inside and outside of your knee, the medial and lateral collateral ligaments prevent movement side to side. The quadriceps and hamstring muscles also play a very important role in keeping the knee joint stable. Tears of the anterior cruciate ligament are occurring with an increasing frequency. Studies have shown that female athletes suffer ACL injuries even more frequently than do their male counterparts. There are several theories of why this injury occurs more often in women.
Women have wider hips, which changes the angle between the femur and tibia.
This may place additional biomechanical strain on the supporting structures of the knee. The tunnel or notch in the femur through which the ACL and PCL pass is often smaller in women then in men. This may play a role in ACL injury as the ligament can be sheared apart by this bony structure. If a female athlete is less muscularly developed then her male counterpart, she will have a comparatively decreased extrinsic support provided by the quadriceps and hamstring muscle groups. Finally, recent studies are addressing this issue on a biochemical level, by looking at estrogen receptors in muscle and ligaments and attempting to determine what role estrogen may play weakening these structures.