Hemarthrosis (Bleeding Into a Joint)

What happens in hemarthrosis

Every joint is enclosed in a capsule lined by a thin membrane, the synovium, which makes a small amount of lubricating fluid. When a blood vessel inside the capsule tears, blood fills the space. Because the capsule is tight, even a small amount of blood raises the pressure and causes pain and stiffness.

Blood is harmful to joint tissue. Iron released from broken-down red cells inflames the synovium, which thickens and grows fragile new blood vessels. These bleed more easily, so one bleed makes the next one more likely. Over time this cycle, called hemophilic arthropathy, wears away cartilage and causes early arthritis. This is why prompt treatment matters.

Hemarthrosis symptoms

• Rapid swelling: after an injury, a joint that swells within minutes to 2 hours usually contains blood. Swelling that builds over 12 to 24 hours is more often clear fluid.
• Tightness and warmth: the joint feels full and tense, and slightly warm.
• Pain that worsens when you try to bend or straighten it.
• Reduced movement: people hold the joint in a slightly bent position, which is most comfortable.
• Bruising around the joint in some cases.

People with hemophilia often describe an early aura: tingling, bubbling or warmth in the joint before any swelling shows. Treating at this stage limits damage. In babies and young children, the first sign may be refusing to crawl, walk or use an arm.

Causes and risk factors

Injury (traumatic hemarthrosis)

Injury is the commonest cause in people without a bleeding disorder. In the knee, a rapid bloody effusion after sport most often means:

• a torn anterior cruciate ligament (the cause in a large share of cases)
• a kneecap dislocation
• a fracture into the joint surface, such as a tibial plateau fracture
• a meniscus tear near its blood supply, or a cartilage fragment breaking off

Fat droplets floating on the blood when the joint is drained suggest a fracture, because marrow fat has leaked from the bone.

Bleeding disorders

• Hemophilia A and B: joint bleeds are the hallmark of severe hemophilia and can happen without any injury. Knees, ankles and elbows are the commonest sites.
• Von Willebrand disease: joint bleeds occur mainly in the severe type 3 form.
• Other rare factor deficiencies and low platelet counts.

Blood thinners

Warfarin, direct oral anticoagulants and antiplatelet drugs increase the risk of spontaneous hemarthrosis, especially in older adults with existing arthritis. See anticoagulant-associated bleeding.

Other causes

• After joint surgery, arthroscopy or joint replacement
• Pigmented villonodular synovitis (tenosynovial giant cell tumor), a benign overgrowth of the synovium
• Severe osteoarthritis or pseudogout in older people
• Blood vessel malformations and, rarely, scurvy or joint tumors

Plantar and foot hemarthrosis

Bleeding can occur into the small joints of the foot and ankle after sprains, fractures and in hemophilia. The ankle is the joint most affected in children with hemophilia. "Plantar" hemarthrosis is not a standard term: pain and bruising on the sole after an injury is more often bleeding into soft tissue or the plantar fascia than into a joint.

Hemarthrosis vs other joint swelling

How hemarthrosis is diagnosed

1. History: how the swelling started and how fast, any pop or giving way, bleeding history in you or your family, and medicines including blood thinners and supplements.
2. Examination: the doctor feels for fluid, checks movement and tests the ligaments, often after the swelling eases.
3. X-ray: looks for fractures and bone fragments.
4. Joint aspiration (arthrocentesis): draining fluid with a needle confirms blood and relieves pressure. It is avoided or done with factor cover in hemophilia.
5. Ultrasound: quickly confirms a joint bleed and is widely used in hemophilia clinics.
6. MRI: shows ligament, meniscus and cartilage injuries.
7. Blood tests: clotting tests (PT/INR, APTT), factor levels, platelets and von Willebrand studies when no injury explains the bleed, or bleeds recur.

Treatment

Immediate care

• Rest the joint and avoid weight-bearing until assessed.
• Ice wrapped in a cloth for 15 to 20 minutes every 2 hours.
• Compression with an elastic bandage and elevation above heart level.
• Pain relief: acetaminophen (paracetamol) is preferred. Avoid aspirin and NSAIDs such as ibuprofen if you have a bleeding disorder or take blood thinners, because they increase bleeding.

Treating the cause

• Hemophilia: prompt clotting factor replacement, ideally within 2 hours of the first symptoms, then a short period of rest and physical therapy. Many patients use regular preventive treatment (prophylaxis) with factor or non-factor medicines such as emicizumab to prevent bleeds.
• Blood thinners: your doctor may check your INR, pause or reverse the medicine if bleeding is significant.
• Injury: draining a large, painful effusion eases pain. The underlying tear or fracture is treated with bracing, physical therapy or surgery.
• Recurrent bleeding into one joint: removing the inflamed synovium (synovectomy), by surgery or a radioactive injection, can break the bleed cycle.

Rehabilitation

Once the bleeding settles, physical therapy restores range of motion and strengthens the muscles that protect the joint. Most people start gentle movement within a few days.

Complications

• Hemophilic arthropathy: chronic pain, stiffness and deformity from repeated bleeds. It may eventually need joint replacement.
• Chronic synovitis: a swollen, boggy joint that bleeds easily.
• Early osteoarthritis after traumatic hemarthrosis, especially with a fracture or ACL tear (post-traumatic arthritis).
• Muscle weakness and contractures from keeping the joint bent.

Outlook

A single hemarthrosis from an injury usually settles within 1 to 3 weeks, and the long-term result depends on the underlying damage. In hemophilia, modern prophylaxis has made joint bleeds far less common, and children treated this way can grow up with largely healthy joints.

Frequently asked questions

What is hemarthrosis?

Hemarthrosis is bleeding into a joint space. It causes rapid swelling, pain and stiffness, usually in the knee, ankle or elbow. It most often follows an injury such as an ACL tear or fracture, or occurs in people with hemophilia or who take blood thinners.

What are the symptoms of hemarthrosis?

The main symptoms are swelling that develops quickly, usually within 2 hours, a tense, warm joint, pain on movement, and holding the joint bent. People with hemophilia often feel tingling or warmth in the joint before visible swelling appears.

How long does hemarthrosis take to go away?

The blood is usually reabsorbed over 1 to 3 weeks. Draining a large bleed with a needle can relieve pain immediately. Recovery from the underlying cause, such as a ligament tear or fracture, often takes longer.

Is hemarthrosis serious?

A single bleed after an injury is usually manageable, but it often signals a significant joint injury. Repeated bleeds, as in untreated hemophilia, damage cartilage and cause permanent arthritis. New hemarthrosis without injury needs testing for a bleeding problem.

Should a joint with blood in it be drained?

A large, tense, very painful bleed is often drained to relieve pressure and confirm the diagnosis. Small bleeds are usually left to resolve. In hemophilia, factor replacement comes first, and drainage is done only with clotting cover.