There are obvious differences in appearance between men and women, which account for differences in sports performance and injury incidence and location. The recent greater exposure of women to high-level sports has produced an increase in the absolute numbers of injuries in women. However, there are marked anatomic differences between men and women in the musculoskeletal system. For example, women naturally have more subcutaneous fat than men, in a characteristic distribution over the buttocks and thighs and behind the upper arms, giving them a more rounded appearance. Skeletal differences are evident in the pelvis, which has larger inlet and outlet to allow for childbirth. Muscle size and muscle development is less in women, due to the physiologic effects of sex hormones. Relaxin in women plays a role in ligament and tendon laxity, allowing women to be generally more supple than men. At times, these anatomic differences are accentuated by feminine fashion, and by the wearing of dress shoes with high heels.