Hemarthrosis

Hemarthrosis is a consequence of laceration of the STA/STV, severely inflamed synovium and retrodiskal tissue upon entry, and laceration of the pterygoid artery during myotomy for anterior release procedures.

Joint Bleeding

Hemarthroses are the most common cause of progressive morbidity in hemophilia. Bleeding into a joint space may occur in the absence of known trauma in patients with severe disease. The joints most commonly involved are the knees, elbows, and ankles.2 To limit long-term joint damage, initial replacement therapy should be instituted as early as possible to raise the plasma factor level to 50% to 70%. For minor or early joint bleeding, an additional factor replacement should be given to maintain a plasma factor level of 30% for approximately 24 hours. For late or significant joint hemorrhage or bleeding in a joint that has been the site of recurrent hemorrhages (target joint), a factor level of 30% should be maintained for 36 to 48 hours. In addition, for all hemarthroses, the joint should be immobilized with a splint for 48 to 72 hours. These recommendations apply to all hemarthroses, regardless of the severity of an individual patient's disease. Children who have had more than one spontaneous hemarthrosis in a single joint are good candidates for future prophylaxis because they are likely to develop progressive joint disease in the affected joint and elsewhere without it.

Hemarthroses

Hemarthroses involve the knees, elbows, ankles, shoulders and hips, in that order; bleeding into the small joints of the hands and feet is unusual. The episodes of joint bleeding begin when the child starts to crawl or walk and are nearly unique to people with FVIII or FIX deficiency. They are most frequent in those with FVIII levels ≤ 0.02 U/mL, and very rare with levels ≥ 0.12 U/mL [15]. As many as 35% of severe hemophiliacs report having ≥ 5 joint hemorrhages in a 6-month time period [13]. Joints are lined by a thin membrane, the synovium, whose functions are maintenance of an intact nonadherent tissue surface, lubrication of cartilage, control of synovial fluid volume and composition, and nutrition of chondrocytes within joints [16]. A dense net of small blood vessels are located just beneath the synovium and are vulnerable to hemorrhage. Ordinary activities such as bending and stretching appear to disrupt these vessels; leakage of blood can only be prevented if the breach is sealed with fibrin. Because fibrin formation is impaired in hemophilia, erythrocytes and other blood constituents gain access to the joint space. Initially, this cellular debri is removed by synovial macrophages, but soon the phagocytic capabilities of these cells are overwhelmed by fresh bleeding [17]. The hemoglobin in the shed red blood cells is degraded to hemosidern, an iron-containing compound that elicits a powerful inflammatory response, typically associated with joint swelling, erythema, and pain [18]. The release of a potent inflammatory and proliferative mediator, tumor necrosis factor alpha, promotes synovial membrane hyperplasia, neovascularization, and the production of enzymes that destroy cartilage and erode the underlying bone [19]. The development of chronic synovitis leads to muscle wasting, stiffness and limited motility, and to the complete destruction of the joint. Prior to the use of prophylactic replacement of FVIII, extensive joint destruction involving knees, ankles, and elbows was common, and crippling was a typical manifestation of hemophilia in boys and young men.

The unique susceptibility to bone and joint destruction in people with hemophilia might be due to dysregulation of cell proliferation. Studies in mice show that the decreased thrombin generation associated with FVIII deficiency reduces proteinase-activated receptor (PAR1) signaling, decreasing the ratio of bone to tissue volume and the number of bony trabeculae [20]. Furthermore, the iron deposited in the joint space triggers expression of mdm2, a p53-binding protein that increases synovial cell proliferation [21]. How these and other factors contribute to the pathobiology of hemophilic arthropathy are subjects for ongoing study.

Joint hemorrhages are associated with intense pain; other descriptors are burning, bubbling, and tingling if nerves are compressed. Fig. 5.1 shows an acute hemarthrosis in the left knee; the joint is swollen, tender, and painful.