Hip joints are relatively simple. Each one comprises a ball at the end of the femur, or thigh bone, which fits into a hole, or socket, in the pelvis.
Both the socket and the head of the femur are coated in cartilage, to ensure they move smoothly together, and the whole joint is covered in a fibrous capsule, which both supports and lubricates the joint.
There are a number of conditions which can cause hip pain, of which the most common is osteoarthritis, a broad-ranging term that can be loosely translated as bone inflammation.
Osteoarthritis in the hip can be caused by localised infection, damage to the cartilage that coats the moving parts of the joint, osteophytes, or bony growths around the edge of the joint. Children can also suffer from a specific type of hip pain known as irritable hip.