Child with knee pain and swelling

A 12-year-old boy, with a story of haemophilia presented with insidious onset of pain and swelling of the left knee over one month, without any history of trauma. Clinical examination revealed an increased volume of the left knee with tenderness and a deficit of flexion and extension.

Initially, we obtained plain knee films, which revealed a widened intercondylar notch, bulging femoral condyles, and flattened condylar surfaces. Additionally, there was a narrowing of the femorotibial joint space and loss of articular cartilage, along with the presence of peri-articular density.

Subsequently, the patient underwent an MRI, which demonstrated a significant synovial fluid effusion in the quadriceps bursa, intercondylar fossa, and popliteal fossa. The MRI also revealed irregularities in the femorotibial plateaus, including subchondral geodes and osteophytic spurs on the femoral and tibial condyles, as well as the patellar base. Furthermore, erosion of the articular cartilage, exposing the bone, and extrusion of the external meniscus were identified. Lastly, the MR study indicated thickening and signal abnormalities in the femoral synovial membrane.

This 12-year-old boy had swelling and pain of the left knee lasting for one month. His clinical history included Haemophilia A with recurrent episodes of left knee swelling.

Haemophilia is the most common severe hereditary haemorrhagic disorder. It is almost always due to a defect or mutation in the gene for the clotting factor. The encoding genes for factors VIII and factor IX are present in the long arm of chromosome X. Haemophilia is characterized by prolonged and excessive bleeding after minor trauma or sometimes even spontaneously [1,2].

The most typical manifestation of haemophilia is haemarthrosis.

During a haemarthrosis, the synovial deposits of haemosiderin result in the release of local inflammation mediators. Villous synovial hyperplasia, infiltration by inflammatory cells, and increased fibroblastic activity are the substrates of this synovitis [3]. Neoangiogenesis associated with this synovial inflammation contributes to the creation of a haemorrhagic vicious cycle due to increased capillary permeability, promoting new episodes of haemarthrosis [4]. Over time, the highly vascularised inflammatory synovial hypertrophy becomes fibrous and acellular.

Independently and concurrently, there is a direct detrimental effect of the presence of intra-articular blood on the cartilage [4–6]. Reactive oxygen species, formed from the iron in intra-articular red blood cells, contribute to chondrocyte apoptosis [4].

Lastly, it should be noted that there is an imbalance in bone remodelling, whether it is solely a consequence of cartilage destruction or is linked to independent factors. This is accompanied by changes in the subchondral bone [5], including osteoporosis, the formation of subchondral cysts, erosions, and the development of osteophytes.

The involvement is typically mono or oligoarticular, with a preference for larger joints like knees, ankles, and elbows. However, it can also impact other joints, such as the shoulder, hip, or hands. Patients develop chronic deformities in one or more joints, which clinically and roentgenographically resemble rheumatoid arthritis [7].

It results in a disabling condition characterised by joint remodelling, chronic pain, and a reduced quality of life. Plain radiographs may reveal periarticular osteoporosis, epiphyseal enlargement with appearances that can resemble juvenile rheumatoid arthritis and paralysis. Additionally, a squared inferior margin of the patella can be observed. These changes can be categorized using the Arnold–Hilgartner classification [10].

MRI is effective in detecting early-stage diseases. T1-weighted sequences provide exceptional visualisation of anatomical structures, including bones. T2-weighted sequences are proficient in detecting inflammatory changes, synovial effusions, and abnormalities in soft tissues, such as a thickened synovium exhibiting low signal intensity due to the haemosiderin susceptibility effect, characteristic of siderotic synovitis. Spin-echo (SE) and gradient-echo (GRE) sequences can be employed to evaluate bone structures and detect potential bleeding or haemarthrosis. Fat suppression sequences aid in enhancing the visualisation of joint structures by reducing fat signals. Consideration may be given to using a contrast agent, such as gadolinium, to assess synovial inflammation, joint effusion, and abnormalities in soft tissues.

Thus, it is very important not only to avoid acute haemarthrosis but also to manage it as efficiently as possible. The etiological treatment of haemophilia relies on replacement therapy with deficient coagulation factor concentrates (via intravenous infusion). These concentrates are traditionally used as quickly as possible in each haemarthrosis to stop the bleeding.

Long-term systematic administration of coagulation factors (several injections per week) started before the age of 2, after the first bleeding, reduces the risk of joint destruction and decreases the number of haemarthroses and life-threatening haemorrhages [8]. Prophylaxis is called “primary” when decided upon in the absence of a prior haemorrhagic incident. This treatment is recommended for all severe haemophilic patients [9].