Your hip joint is made up of 2 bony components that meet in a “ball and socket” configuration, allowing a wide range of motion of your hip while at the same timemaintaining stability. Your femur (thigh bone) has a long shaft which is topped by the femoral head, a ball of bone that sits inside the acetabulum (cup-shaped socket) of your pelvis. The bony surfaces are covered in protective articular cartilage which allows them to glide over each other with little friction.
The surface area of the acetabulum is increased by the labrum, a strong rubbery ring sitting around the rim of the socket which acts as a “shock absorber” while also making the hip joint more stable. The whole joint is enclosed by a tough, fibrous joint capsule which is thickened in several places to form ligaments. These ligaments function like robust rubber bands, protecting the hip joint by limiting extremes of range of motion and keeping the femoral head “ball” sitting snuggly inside the acetabular “socket.” The capsule also contains a small amount of synovial fluid which lubricates and nourishes the hip joint.
Several powerful muscle groups move the hip joint. Most of the hip flexor muscles originate inside the torso, extending downwards to cross the front of the hip joint and attach to your femur. When they are activated, they pull the thigh forward such as when you pick up your leg to walk up stairs. The hipextensormuscles are located at the back of your hip and thigh and when they contract, move your hip so that your leg extends behind you. The abductor muscles lift your leg out to the side and are mostly located in your buttock and outside of your thigh. Lastly, the adductor muscles are located on the inside of your thigh and pull your leg inwards for example, squeezing your knees together.