The joint changes in hemophilia are secondary to chronic repetitive hemarthrosis and intraosseous bleeding. Hemarthrosis occurs in 75 to 90 percent of patients with hemophilia. The first bleed usually occurs between the ages of 2 and 3. Repetitive bleeding episodes occur between the ages of 8 and 13, with 50 percent of patients developing permanent bone changes around the joint. The radiographic change in the joint depends upon the age of the patient at the time of the bleed, the site of the bleed, and the acuteness or chronicity of the bleed. The articular changes in hemophilia are as follows:

• 1.
  

  Radiodense soft tissue swelling

  
  
• 2.
  

  Osteoporosis—juxta-articular or diffuse

  
  
• 3.
  

  Overgrown or ballooned epiphyses

  
  
• 4.
  

  Subchondral cysts

  
  
• 5.
  

  Late uniform joint space loss

  
  
• 6.
  

  Late secondary osteoarthritic changes

  
  
• 7.
  

  Asymmetrical sporadic distribution

  
  
• 8.
  

  Distribution in knee, elbow, ankle, hip, and shoulder, in decreasing order; changes distal to the elbow or ankle are rare

Radiographic changes of hemophilia resemble those of juvenile idiopathic arthritis (JIA) except that there is usually no periostitis or bone ankylosis.

The knee

The knee is the joint most commonly involved in hemophilia. In the acute hemarthrosis, joint effusion and juxta-articular osteoporosis are observed. If chronic bleeding occurs, the joint effusion becomes radiodense ( Fig. 22-1 ). Chronic hyperemia to the joint leads to overgrowth or ballooning of the femoral and tibial epiphyses. The overgrowth of the femoral condyles causes widening of the intercondylar notch. This widening may be accentuated by the position of the knee, which is frequently held in fixed flexion. The condyles may appear flattened. The patella is ballooned and squared inferiorly. Multiple subchondral cysts are usually visualized in the epiphyses ( Fig. 22-2 ). If the chronic bleeding occurs in an older child, then the overgrowth of the epiphyses and widening of the intracondylar notch may not be as apparent as it is in the younger child ( Fig. 22-3 ). In chronic phases of the disease, there may be uniform joint space loss with secondary osteoarthritic changes ( Fig. 22-4 ).

Lateral view of the knee in a patient with hemophilia. A radiodense effusion is present. There is overgrowth of the epiphyses, as well as ballooning and squaring of the patella.

Anteroposterior (AP) ( A ) and lateral ( B ) views of knee in patient with hemophilia. There is overgrowth of the epiphyses, widening of the intracondylar notch, ballooning of the patella, and squaring of its inferior border. Subchondral cysts are present.

AP view of the knee in a 53-year-old patient with hemophilia. The overgrowth of the epiphyses and widening of the intracondylar notch are not as easily discernible as in Figure 22-2 . There is uniform loss of the joint space and a subchondral cyst is present ( arrow ).

A, AP view of the left knee in a patient with longstanding hemophilia. The radiographic changes are those of chronic disease. There are ballooning of the epiphyses and widening as well as deepening of the intracondylar notche. There is flattening of the femoral condyles. There are superimposed secondary osteoarthritic changes. B, Sagittal fat-suppressed T2-weighted image in the same patient shows low signal synovitis ( arrows ) that might be confused with pigmented villonodular synovitis.