Joint Infection
Infection inside a joint requiring urgent treatment
Quick Facts
- Type: Joint (musculoskeletal) infection
- Usual cause: Bacteria entering the joint
- Key features: Sudden joint pain, swelling, warmth, fever
- Urgency: Medical emergency needing prompt treatment
Overview
A joint infection, also called septic arthritis, is an infection inside a joint space. It usually occurs when bacteria reach the joint and multiply, causing intense inflammation. The knee is the most commonly affected joint, but the hip, shoulder, ankle, wrist, and other joints can be involved. A joint infection is a serious medical condition that needs prompt diagnosis and treatment.
Without quick treatment, the infection can rapidly damage the cartilage and bone within the joint, leading to permanent joint damage and disability. The infection can also spread into the bloodstream and become life-threatening. Because of these risks, sudden severe joint pain with swelling, warmth, and fever should be treated as an emergency and evaluated urgently.
Symptoms
The symptoms of a joint infection usually come on quickly, often over hours to a day or two, and typically affect a single joint.
- Sudden, severe pain in the joint, worse with movement
- Swelling of the joint
- Warmth and redness over the joint
- Difficulty or inability to move or bear weight on the joint
- Fever and chills
- Feeling generally unwell
In babies, young children, and some older or immunocompromised adults, symptoms can be less obvious, with irritability, refusal to use a limb, or simply appearing unwell. Any sudden, hot, swollen, very painful joint should prompt urgent medical attention.
Causes
Joint infections occur when an infecting organism, most often bacteria, reaches the joint.
- Bloodstream spread: bacteria from an infection elsewhere in the body travel through the blood and settle in a joint.
- Direct entry: a wound, injection, joint injury, or surgery can introduce germs directly into the joint.
- Spread from nearby tissue: an infection in the surrounding skin, soft tissue, or bone can extend into the joint.
Most joint infections are caused by bacteria, but viruses and fungi can occasionally be responsible. People with damaged or artificial joints, or with weakened immune systems, are at higher risk.
Risk Factors
- Existing joint disease such as rheumatoid arthritis or osteoarthritis
- An artificial (prosthetic) joint
- A weakened immune system from illness or medications
- Diabetes
- Recent joint injury, injection, or surgery
- Skin infections or open wounds
- Injecting drug use
- Very young or older age
Diagnosis
Rapid diagnosis is essential. Doctors combine the examination with tests of the joint fluid and blood.
- Joint fluid analysis: a sample of fluid drawn from the joint with a needle is examined for infection-fighting cells, bacteria, and crystals; this is the key test.
- Blood tests: measure markers of infection and inflammation and may detect bacteria in the blood.
- Imaging: X-rays, ultrasound, or MRI to assess the joint and look for fluid and damage.
- Cultures: growing the organism from joint fluid or blood helps identify it and guide antibiotic choice.
Treatment
A joint infection is treated urgently, usually in hospital, to clear the infection and protect the joint. The two main parts of treatment are antibiotics and drainage of the joint.
- Antibiotics: started promptly, often given into a vein at first, then adjusted once the organism is identified and continued for several weeks.
- Joint drainage: removing the infected fluid through a needle, with a scope (arthroscopy), or by open surgery to clear pus and reduce damage.
- Removal of infected hardware: an infected artificial joint may need surgery to clean or replace it.
- Supportive care: pain relief, rest, and later physical therapy to restore movement and strength.
Early treatment greatly improves the chance of preserving the joint.
Prevention
Joint infections cannot always be prevented, but some steps lower the risk.
- Clean and care for wounds promptly and watch for signs of infection
- Treat skin and other infections early before they can spread
- Manage chronic conditions such as diabetes and joint disease
- Follow care instructions carefully after joint injections or surgery
- Seek prompt care for a sudden hot, swollen, painful joint rather than waiting
When to See a Doctor
A joint infection is a medical emergency. Seek urgent care or go to the emergency department right away if you have:
- Sudden, severe pain in a single joint that you cannot move or bear weight on
- A joint that is swollen, hot, and red
- Fever, chills, or feeling very unwell along with joint pain
- A child who refuses to use a limb, or an artificial joint that becomes painful and swollen
Prompt treatment is vital to prevent lasting joint damage.
Frequently Asked Questions
Is a joint infection an emergency?
Yes. A joint infection, or septic arthritis, is a medical emergency. Without prompt treatment it can quickly damage the joint and may spread to the bloodstream. A sudden, hot, swollen, very painful joint with fever should be evaluated urgently.
How does a joint become infected?
Bacteria can reach a joint through the bloodstream from an infection elsewhere, enter directly through a wound, injection, injury, or surgery, or spread from a nearby infection in the skin or bone. Most joint infections are caused by bacteria.
How is a joint infection treated?
Treatment usually involves hospital care with antibiotics, often given into a vein at first, and drainage of the infected fluid from the joint with a needle, a scope, or surgery. Early treatment helps preserve the joint and prevent lasting damage.
Who is most at risk of a joint infection?
People with existing joint disease, artificial joints, diabetes, a weakened immune system, recent joint injury or surgery, skin infections, or injecting drug use are at higher risk. Very young children and older adults are also more vulnerable.
Can a joint infection cause permanent damage?
It can. If treatment is delayed, the infection can rapidly destroy cartilage and bone within the joint, leading to lasting stiffness, pain, or disability. This is why fast diagnosis and treatment are so important.
References
- MedlinePlus, U.S. National Library of Medicine. Septic arthritis.
- Mayo Clinic. Septic arthritis — Symptoms and causes.
- American Academy of Orthopaedic Surgeons. Septic Arthritis.
- National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Infectious Arthritis.