The hip flexor muscles lie under your abdominal muscles. A group of muscles that includes the psoas major and minor, iliacus, sartorius and rectus femoris, the hip flexors connect your thighs to your pelvis. When they contract, these muscles bring your thigh and torso closer together.

The American Academy of Orthopaedic Surgeons defines a hip fracture as a break in the upper quarter of the thigh bone. Approximately 90 percent of hip fractures occur among adults age 65 and older, according to the Centers for Disease Control and Prevention.

Hip osteoarthritis is a debilitating condition caused by wearing down of the cartilage, or padding, in your hip joint. Walking causes severe pain as the bones in this ball-and-socket joint rub together. Joint replacement surgery is performed to decrease pain and improve mobility.