Radiological features of haemophilic arthropathy

Clinical History

This patient presented with complaints of a swollen and painful right knee, which he had had for the past 2-weeks. At physical examination, the knee was swollen, hot and tender. The patient was unable to bear his weight . There was a fixed flexion deformity at 30 degrees.

Imaging Findings

This patient presented with complaints of a swollen and painful right knee, which he had had for the past 2-weeks. The knee was swollen, hot and tender, the patient was unable to bear his weight, and there was a fixed flexion deformity at 30 degrees. During his childhood, he had had several spontaneous episodes of haemarthrosis in his right knee but none since then. Plain radiographs of the right knee showed a soft tissue swelling with diffuse calcification of the synovial membrane. There was a coarsening of a trabecular pattern in both tibial and femoral epiphyses due to osteopenia, and the joint space was also reduced. Following this, he had an MRI of the knee, which was performed using a 0.5 Tesla system. T2-weighted images demonstrated a large joint effusion with prominent hypointense synovial tissue affecting the whole joint. This appearance is in keeping with haemosiderin laden tissue from chronic recurrent intra-articular bleeding. Secondary osteoarthritis affecting all the three compartments of the knee with thinning of the articular cartilage especially over the weight-bearing portions and subchondral cysts were also seen. He was known to suffer from haemophilia A from his childhood and was also a carrier of Hepatitis C and HIV. Forty-eight hours prior to admission, the patient had increased his dose of Human Antihaemophilic (Factor VIII) Fraction from 1000U, thrice a week, to 2000U, twice daily. On admission, his Factor VIII level was 110% of the normal level, and hence the same dose was continued for 2 more days. It was then reduced to 1000U, twice daily, as the Factor VIII level increased to 135%. The patient underwent physiotherapy regularly. He continued to improve gradually and was discharged a week after admission.

Discussion

Haemophilias are known to be inherited bleeding disorders. Haemophilia A is caused by a deficiency of Factor VIII. Factor VIII plays an important role in the coagulation pathway by maintaining a sufficient amount of Factor Xa needed to produce thrombin. Bleeding occurs due to a failure of secondary haemostasis. This is due to the fibrin plug not being stabilised because of inadequate amounts of thrombin being generated [1]. Haemophilia is diagnosed either based on the family history or after an episode of bleeding. The severity of the disease is classified based on the concentration of the level of Factor VIII. It is considered to be “severe” if the levels are less than 1% of normal values, “moderate” if it is between 1–5% and “mild” if more than 5%. The hallmark of severe haemophilia is spontaneous haemarthrosis and bleeding into muscles [1]. Haemophilia is currently incurable, and the present treatment involves raising the level of Factor VIII sufficiently so as to stop bleeding [1]. Recurrent haemarthrosis results in synovial membrane inflammation and villous hypertrophy. Haemosiderin accumulates within the synovial macrophages. This hypertrophied synovium is hyperaemic and is more prone to injury. This leads to a cycle of further bleeding and damage to the cartilage and the subchondral bone. Hyperaemia causes periarticular osteoporosis and epiphyseal overgrowth. Multiple subchondral cysts that are thought to develop due to intraosseous haemorrhage are typical of haemophilic arthropathy. The commonly involved joints are the knee, elbow, ankle, hip and the shoulder [2]. Based on the radiographic changes observed, the stage of the disease is classified using the Arnold–Hilgartner scale from I to V. In Stage I, there is a soft tissue swelling or effusion with normal bone and joint surfaces. In Stage II, there is periarticular osteoporosis and an overgrowth of the epiphysis before fusion takes place. In Stage III, there are osseous erosions, sclerosis and subchondral cysts, but the joint space is preserved. In Stage VI, there is a focal or diffuse joint space narrowing. In stage V, the joint is contracted with severe degenerative changes [2]. The main differential diagnoses are pigmented villonodular synovitis (PVNS), and haemorrhagic synovitis. In PVNS, the knee joint is most commonly involved and is typically found in females between 20–50 years of age. Radiologically, there is an absence of calcification within the hyperplastic synovium, and there are sclerotic rimmed bone erosions on both the articular surfaces [3]. On MRI, the hypertrophic synovium laden with haemosiderin gives a low signal on both T1-w and T2-w sequences [4]. Haemorrhagic synovitis can also mimic haemophilic arthropathy, but most often, there is a history of trauma which differentiates between the two conditions [3]. A rare but severe complication of haemophilic arthropathy is a haemophilic pseudotumour which is a chronically encapsulated collection of blood. It is commonly found in adults, usually presenting as a pathological fracture and occurs commonly in the femur and the pelvis. It can appear as a soft tissue mass, lytic lesion or a large destructive mass when seen on radiographs [2]. MRI can help diagnose haemophilic arthropathic changes much earlier than other imaging modalities can. Due to the presence of very-low-signal intensity of a clot within a high-signal intensity joint effusion, following haemarthrosis, fluid level is conspicuous on T2-weighted images. The chronically inflamed haemosiderin synovial membrane has an intermediate to low signal intensity on T1images and a very-low-signal intensity on T2-weighted images. Subchondral cysts and osteochondral lesions not seen on radiographs can be seen on MRI [2].

Differential Diagnosis List

Final Diagnosis

Haemophilic arthropathy.

URL:	https://eurorad.org/case/3182
DOI:	10.1594/EURORAD/CASE.3182
ISSN:	1563-4086