Femoroacetabular joint
The femoral head fits deeply into the acetabulum, providing substantial bony stability while still allowing flexion, extension, rotation, and abduction.
The hip joint is formed where the rounded head of the femur fits into the deep, cup-shaped acetabulum of the pelvis, an arrangement that provides substantial inherent stability compared with more shallow joints like the shoulder.
A large group of muscles surrounds the joint, including powerful hip flexors at the front, extensors at the back, and abductors at the side that are essential for controlling pelvic stability during single-leg activities such as walking and running.
Key structures
Acetabular labrum
A ring of cartilage around the rim of the socket increases joint contact area and stability, and can be a source of pain when torn.
Gluteus medius
This hip abductor muscle controls pelvic tilt during walking and running, and its weakness is commonly associated with greater trochanteric pain syndrome and altered gait mechanics.
Iliopsoas
This deep muscle group flexes the hip and can become a source of anterior hip or groin pain when irritated, particularly in activities involving repetitive hip flexion such as kicking or sprinting.
Hamstrings (proximal attachment)
The hamstring muscles originate at the base of the pelvis and extend the hip, and this attachment point can become a source of deep buttock pain when irritated.
Hip capsule and ligaments
A thick fibrous capsule reinforced by several ligaments limits excessive joint motion and works alongside the surrounding muscles to maintain stability.
Planes & range
Hip flexion, bringing the knee toward the chest, represents the joint's largest range of motion, while extension is considerably more limited at roughly 10–20° due to the tension of anterior hip structures.
This combination of deep bony stability and powerful surrounding muscles explains why hip pain can originate from the joint itself, the surrounding tendons, or the muscles that control pelvic movement, each requiring a different assessment focus.
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