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X-ray diagnosis of osteoarthritis of the hip joints (coxarthrosis)
Last reviewed: 08.07.2025
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The accuracy of assessing the width of the joint space in the hip joints is determined by the correct positioning of the patient, rotation of the limb and centering of the X-rays during radiography. In the standing position of the patient, the width of the joint space is reliably smaller than in the lying position. The joint space is narrowed to a greater extent when the foot is turned inward. It is recommended that the central X-ray beam pass through the center of the femoral head, since shifting the X-ray tube away from the center of the joint can reliably change the width of the joint space. However, separate radiography of the hip joints leads to an increase in the radiation load on the patient.
In the initial stages of coxarthrosis (stages I-II according to Kellgren), X-ray examination reveals:
- slight narrowing of the radiographic joint space,
- mild subchondral osteosclerosis,
- point calcifications in the area of the outer edge of the roof of the acetabulum (initial signs of osteophytosis),
- sharpening of the edges of the fossa of the head of the femur in the area of attachment of the round ligament of the head of the femur.
In the late stages of osteoarthritis of the hip joints (stages III-IV according to Kellgren) the following are observed:
- progressive narrowing of the joint space,
- the formation of osteophytes of various shapes and sizes on the edges of the articular surfaces of the acetabulum, the head of the femur, which is why it can acquire a mushroom shape. In the middle part of the acetabulum, a wedge-shaped osteophyte may form, which can cause lateral displacement of the head of the femur,
- deepening of the acetabulum, which can be caused by the growth of osteophytes (its protrusion is possible against the background of osteoporosis or thinning of the bones that make up the bottom of the acetabulum),
- pronounced subchondral osteosclerosis, which manifests itself initially in the area of the roof of the acetabulum, then in the upper part of the femoral head,
- in advanced cases - a decrease in volume and flattening of the articular surface of the femoral head against the background of pronounced cystic restructuring of bone tissue, alternating with areas of subchondral osteosclerosis,
- bone cysts - single or multiple - occur in the upper part of the acetabulum or in the area of greatest load on the articular surface of the femoral head,
- aseptic necrosis of the femoral head,
- subluxations of the femur: more often upward/laterally, less often upward/medially,
- compaction of bone tissue and shortening of the femoral neck,
- free intra-articular bodies (rarely detected in coxarthrosis).
In secondary dysplastic coxarthrosis, all radiographic symptoms develop early (at a young or middle age) and can result in aseptic necrosis of the femoral head and subluxation or complete dislocation of the hip.
Ischemic coxarthrosis with rapid narrowing of the joint space, restructuring of the bone structure in the head and neck of the femur, early osteosclerotic changes, but without significant osteophytosis, with fairly rapid development of destruction of the femoral head, is also described.