Pathomechanism and imaging modalities
Recurrent intra-articular haemorrhages trigger a cascade of pathological reactions. Blood overloads the synovial membrane with breakdown products (primarily haemosiderin), causing its hypertrophy, chronic inflammation, and gradual destruction of cartilage tissue. The following modalities are used to visualise these changes:
- Radiography: traditionally used to assess severity using the Pettersson score (Pettersson score). The main disadvantage of the method is its insensitivity to the earliest soft-tissue changes.
- Ultrasound: successfully demonstrates acute or chronic haemarthrosis and developing synovitis, although it is less effective at visualising the condition of cartilage and subchondral bone.
- MRI: the absolute method of choice. It enables the detection of intra-articular blood clots against a background of hyperintense effusion, as well as fluid-fluid levels (fluid-fluid levels). The T2 gradient-echo* sequence is extremely important as it highlights the magnetic susceptibility artifact (blooming artifact) specific to haemosiderin deposits in the synovium. 3D spoiled gradient-echo and fast spin-echo sequences help identify early focal defects and cartilage thinning.
Radiological stages (I–V)
Classical radiological staging distinguishes five sequential stages in the progression of haemophilic arthropathy:
- Stage I: Only soft-tissue swelling and/or joint effusion is observed. Articular surfaces are intact.
- Stage II: Periarticular osteoporosis is added to the findings of stage one. Epiphyseal overgrowth (epiphyseal overgrowth) occurs due to chronic hyperaemia.
- Stage III: Bone erosions, sclerosis, and subchondral cysts appear, while joint space width is still preserved.
- Stage IV: The classical features of stage three are complemented by focal or diffuse joint space narrowing.
- Stage V: A stiff, contracted joint forms with massive degenerative changes. In non-weight-bearing joints, osteolysis can become so pronounced that the radiological appearance falsely mimics the state following surgical amputation.
Specific patterns in various joints
Each joint exhibits characteristic imaging patterns of involvement:
- Knee joint: Enlargement of the distal femoral epiphysis and proximal tibial epiphysis, varus or valgus deformity are observed. Typical findings include widening of the intercondylar notch and a characteristic "squaring" (squaring) of the inferior pole of the patella accompanying its hypertrophy.
- Elbow joint: Due to hyperaemia, ossification centres appear prematurely and the radial head hypertrophies. Pressure erosion of the radial notch of the ulna occurs, the trochlear notch widens, and large lytic lesions appear.
- Ankle joint: The distal tibial epiphysis grows asymmetrically, causing medial tilting of the joint space (medial tibiotalar slant). The talar dome is markedly flattened, and cysts form. In rare cases, the process ends in ankylosis.
- Hip joint: Haemorrhages can mimic osteonecrosis (Perthes' disease appearance), ultimately leading to the development of coxa magna. Acetabular protrusion, coxa valga (due to delayed axial loading), and slipped epiphysis secondary to bleeding into the growth plate are possible.
Haemophilic pseudotumour
Haemophilic pseudotumour (haemophilic pseudotumour) is a rare but formidable complication resulting from progressive haemorrhages near muscle attachment sites, often without any history of trauma. It occurs in approximately 1.5% of adult patients.
The process most commonly localises to the pelvic bones (especially the iliac wing near the origin of the iliacus muscle), as well as the femur and lower leg. Radiographs reveal a soft-tissue calcified mass with "geographic" lytic destruction of the adjacent bone. CT visualises a hyperdense pseudocapsule with a hypodense centre, while MRI shows characteristic peripheral nodules and a hypointense wall (haemosiderin accumulation). The initial manifestation of a pseudotumour may be a pathological fracture. Important: diagnostic surgical interventions should be strictly avoided when a pseudotumour is suspected.
Briefly: answers to topical questions
Which conditions are included in the differential diagnosis of haemophilic arthropathy?
Differential diagnosis of haemophilic arthropathy is carried out with pigmented villonodular synovitis and Perthes' disease.
- Pigmented villonodular synovitis (Pigmented Villonodular Synovitis) — differentiated from haemophilia and synovial haemangioma.
- Perthes' disease (Perthes' disease) — hip joint involvement in haemophilia can mimic this condition due to similar radiological signs of osteonecrosis.
Which joints are classified as "target joints" and are most frequently affected in haemophilia?
The "target joints" most frequently affected in haemophilia are predominantly large joints.
- Knee joint (Knee joint) — is the most frequently affected joint.
- Elbow joint (Elbow joint) — a typical localisation for haemorrhages.
- Ankle joint (Ankle and foot) — belongs to the frequently affected large joints.
- Hip joint (Hip joint) — belongs to the frequently affected large joints.
- Shoulder joint — is also among the frequently affected large joints.
For quick memorisation of arthropathy stages: S-O-E-N-S (Swelling → Osteoporosis → Erosions → Narrowing → Stiffness).
Class and exam questions
Why might soft tissues appear radiodense on radiographs in haemophilic arthropathy?
This is due to hypertrophy of the synovial membrane, which accumulates large amounts of blood breakdown products (primarily haemosiderin) that increase its radiodensity.
Which well-known hip joint disease can haemophilic arthropathy mimic?
In the hip joint, haemorrhages can produce the appearance of typical osteonecrosis, visually mimicking Perthes' disease.
Why is T2* gradient-echo preferred for evaluating arthropathy on MRI?
The T2* gradient-echo sequence is most sensitive to magnetic susceptibility artifacts, allowing extremely precise detection of haemosiderin deposits as areas of markedly hypointense signal.
What else to study on this topic
- Clinical application of the Pettersson score
- MRI differential diagnosis with pigmented villonodular synovitis
- Evolution of the MRI signal of a haemophilic pseudotumour depending on the age of the haemorrhage
- Skeletal manifestations of primary and secondary synovial osteochondromatosis
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