Stage 1 | Minor changes on radiograph | 25% |
Stage 2 A | Sclerosis or cysts of femoral head, diffuse porosis | 25% |
Stage 2 B | Crescentic subchondral line, flattening of the femoral head | 28% |
Stage 3 | Broken contour of the head, normal joint space | 16% |
Stage 4 | Collapse, flattened contour of the femoral head, decreased joint space, osteoarthritis | 6% |