Copyright 2009
Definition
Hemarthrosis of the knee is blood within the knee joint and is a clinical finding that can be seen in a number of traumatic injuries or in the non-traumatic setting of disease. It can be seen in the setting of injury to the ACL or PCL, articular chondral surface, fractures or dislocations of the femur, tibia, or patella, meniscal tears, or fractures of the intercondylar eminance. In the non-traumatic setting, hemarthrosis can be seen in pigmented villonodular synovitis, hemangioma, hemophilia, sickle cell disease, anticoagulant therapy, AV fistulas, thrombocytopenia, among other disorders.
Hemarthrosis is characterized by a tense effusion in the knee joint which makes flexion and extension as well as ambulation difficult. Aspirating the knee can decrease discomfort and make physical examination easier.
Blood within the joint usually doesn’t cause problems in and of itself, but in the setting of continual hemarthrosis in chromic disease such as PVNS and hemophilia, eventual degeneration of cartilage can occur.
Diagnosis of a hemarthrosis is based on history and physical and definitively made with aspiration. Finding the cause of a hemarthrosis is essential since there is always an accompanying problem that needs to be addressed. The ACL is torn in up to 50% of cases of hemarthrosis in the setting of a sporting injury. Fat globules (from the bone marrow) in the aspirate will clue a practitioner to look for a fracture.
Imaging includes the use of x-rays which can show an effusion of the knee with blunting of the empty spaces of the knee and distension of the joint capsule. MRI can often help in delineating the cause of a hemarthrosis, and CT can be helpful in the setting of a fracture which is the cause of hemarthrosis.
Treatment options depend on the cause of the hemarthrosis. Aspiration is typically performed to allow easier motion of the knee and enable a more accurate exam of the knee.
References
http://www.wheelessonline.com/ortho/differential_dx_of_hemarthrosis