The hip is a ball and socket joint that connects the thigh bone (femur) to the pelvis (acetabulum). The hip joint is the largest weight bearing joint in the body. The hip joint is surrounded by strong ligaments and muscles.
There are two main bone structures that make up the hip.
- Femoral head – a ball shaped piece of bone at the top of the femur.
- Acetabulum – the cup-like socket in the pelvis that the femoral head fits into.
There are several types of tissue in the hip joint.
- Cartilage – Both the femoral head and the acetabulum are lined with cartilage. Cartilage creates a smooth surface for the bones to glide over one another without friction and acts as a shock absorber in high impact activities.
- Synovium – A thin membrane called synovium exists between the femoral head and the acetabulum. It produces fluid which lubricates the joint and adds additional cushioning to support smooth movement.
- Ligaments – Bands of fibrous tissue known as ligaments hold the femoral head in the acetabulum. The purpose of these ligaments is to hold the femoral head in place and to increase stability.
- Muscles and tendons – large muscles surround the hip to add further support and enable movement. Tendons connect the muscles to the bones.
Blood vessels and Nerves
Major blood vessels and nerves pass the hip joint to supply the lower limbs with blood and sensory and motor function.
The ball and socket function of the hip joint ensures a wide range of movement of the lower limbs.
- Flexion is the movement of lifting your leg out in front of you.
- Extension is the movement of lowering your lifted or moving your leg behind you.
- Adduction is the movement of lifting your leg inward to cross your leg over the midline in front of you
- Abduction is the movement of lifting your leg out to the side
- Rotation is the the movement of turning your leg clockwise and anticlockwise.
- Circumduction is the circular movement produced by moving your leg in an arc.