Hemarthrosis is a bleeding

Bleeding

Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood or blood escape from the circulatory system...

 into joint

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

 spaces.

Causes

It usually follows injury

Injury

-By cause:*Traumatic injury, a body wound or shock produced by sudden physical injury, as from violence or accident*Other injuries from external physical causes, such as radiation injury, burn injury or frostbite*Injury from infection...

 but occurs mainly in patients with a predisposition to hemorrhage such as those being treated with warfarin

Warfarin

Warfarin is an anticoagulant. It is most likely to be the drug popularly referred to as a "blood thinner," yet this is a misnomer, since it does not affect the thickness or viscosity of blood...

 (or other anticoagulant

Anticoagulant

An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...

s) and patients with hemophilia.

It can be associated with knee joint arthroplasty

Arthroplasty

Arthroplasty is an operative procedure of orthopedic surgery performed, in which the arthritic or dysfunctional joint surface is replaced with something better or by remodeling or realigning the joint by osteotomy or some other procedure.-Background:Previously, a popular form of arthroplasty was...

.

Treatment

In hemophilia it may occur spontaneously, and recurrent hemarthroses are a major cause of disability

Disability

A disability may be physical, cognitive, mental, sensory, emotional, developmental or some combination of these.Many people would rather be referred to as a person with a disability instead of handicapped...

 in that patient group due to hemophilic arthropathy, requiring synovectomy

Synovectomy

Synovectomy is the surgical removal of a part of the synovial membrane of a synovial joint.-Indications:It is one of the treatment options for certain diseases involving the synovium like:* Severe rheumatoid arthritis or juvenile idiopathic arthritis...

, joint replacement

Joint replacement

Replacement arthroplasty [from Greek arthron, joint, limb, articulate, + -plassein, to form, mould, forge, feign, make an image of], or joint replacement surgery, is a procedure of orthopedic surgery in which the arthritic or dysfunctional joint surface is replaced with an orthopaedic prosthesis...

and increased medical therapy to prevent further bleeding episodes, although it is controversial whether clotting factor administration adequately prevents hemarthroses.

Complications

Up to a quarter of all severe ligament or capsular knee injuries leading to a haemarthrosis are associated with cartilage damage that can lead to progressive degenerative arthritis.