If your joint feels warm, hot, or swollen, this generally signals inflammation due to injury, infection, or an underlying disease process. Joint warmth can affect one or more joints, and the pattern of involvement, timing, and associated symptoms differ depending on the cause.
Diagnostic tests can include imaging, and/or needle aspiration of fluid—and treatment may be necessary. Causes
Joint warmth is often be accompanied by pain, stiffness, and swelling. Inflammation, which can produce swelling and elevate your body temperature, is the body's way of alleviating infections and injuries. Often, rheumatic diseases, autoimmune diseases, and cancer can cause inflammation as well.
Joint trauma from an acute injury can occur as a result of sports, a fall, or a blunt-force impact. The trauma may affect the bone, muscles, tendons, ligaments, cartilage, and other structures within the joint.
Among some of the more common joint injuries:1
Dislocation: Subluxation is a partial separation of the bones in a joint, while dislocation, also described as luxation, is a full separation.
Fracture: A broken bone.
Sprains: The ligaments that hold the joint bones together can become damaged or partially torn by overstretching or twisting.
Strains: Muscle or tendon damage or partial tears ("pulled") can occur due to overstretching.
More than one of these injuries can occur together. They typically involve the ankle, knee, wrist, or shoulder joints. One of the most common joint injuries is an anterior cruciate ligament (ACL) tear, a knee injury that frequently happens during sports.
While the pain from a traumatic injury is usually immediate, it can sometimes feel like a minor knock, only to progressively worsen over hours or days—with joint warmth, bruising, stiffness, swelling, and joint deformity.
Infections of the joint may be caused by a penetrating injury that introduces a pathogen (infectious organism), usually a bacterium, into the joint space.2 A systemic (whole-body) infection can seed the joint with bacteria from the bloodstream, especially if your immune system is impaired.
Infections that can cause a warm joint include:
Septic arthritis: Infection of a joint by bacteria or fungus. Bacterial septic arthritis is most often the result of seeding from a bloodstream infection3 or contamination after joint surgery.
Lyme disease: A tick-borne illness caused by the bacterium Borrelia burgdorferi. It causes joint pain and inflammation, alongside a characteristic "bull's eye" rash and flu-like symptoms.4
Cellulitis: A serious and potentially life-threatening bacterial infection of the skin that may look and feel like arthritis.
Osteomyelitis: A bacterial infection of the bone that can arise when a bacterial infection elsewhere in the body, such as a urinary tract infection or pneumonia, spreads to the bones. Diabetes or sickle cell disease can make you especially vulnerable to osteomyelitis.5
Reactive arthritis: This isn't a joint infection—it is a form of arthritis that develops in response to a bacterial infection elsewhere in the body, often days or weeks earlier.
Rheumatic fever: An uncommon illness associated with inadequately treated strep throat or scarlet fever. Multiple-joint inflammation is one of the telltale signs of rheumatic fever.6
Joint warmth, fever (mild to high-grade), and malaise are the most common signs of a joint infection. Other symptoms include joint pain, redness, swelling, and stiffness. An infection from a penetrating wound may also produce a discharge.
Seek emergency care if you have joint pain with a fever of over 100.4 F, shaking chills, or red streaks on your skin (a sign of cellulitis).
Rheumatic diseases cause chronic or intermittent pain and inflammation in the joints, muscles, or connective tissues. Some of these conditions are associated with age or repetitive use, while others are caused by an autoimmune disease in which the immune system attacks its own cells and tissues.
Osteoarthritis is the classic "wear-and-tear" arthritis in which joint cartilage is gradually worn down over time, causing joint stiffness, deformity, and restriction of motion.7
Among the conditions caused by an autoimmune or inflammatory disease:
Gout: Caused by the progressive deposit of uric acid crystals in the joint space, most predominately the big toe.
Polymyalgia rheumatica: An inflammatory disorder that causes pain and stiffness, especially in the shoulders, usually affecting people over age 65.8
Psoriatic arthritis: A form of arthritis that frequently develops with psoriasis.
Rheumatoid arthritis: The most common form of autoimmune arthritis in which arthritic pain is most often bilateral (affecting the same joints on both sides of the body).9
Juvenile idiopathic arthritis: The most common form of arthritis in children and adolescents.
A key characteristic of rheumatic diseases is the recurrence of symptom flares, also known as exacerbations.
When to See a Doctor
Though you may be able to go about your day unbothered by a warm joint, you shouldn't ignore it. You should seek medical attention if it doesn't begin to improve within a day, or if you don't know the cause. If needed, your primary doctor might refer you to a rheumatologist for further investigation.
If a joint is suddenly and excessively hot, don't wait a day or two to have it looked at. Go the nearest walk-in clinic, urgent care center, or emergency room if your doctor is unable to see you, especially if the joint is painful, swollen, or visibly deformed.
If the pain is extreme and accompanied by fever, chills, dizziness, irregular heartbeat, changes in skin color or appearance, seek emergency care irrespective of whether you have had a recent injury or surgical procedure. Symptoms like these rarely resolve on their own and may lead to a medical crisis if left untreated.
In addition to your joint warmth, your doctor will consider your other symptoms and review your medical history, family history, medications, and discuss with you any injury, infection, or medical procedure you may have recently had.
Your physical examination would show whether you have joint pain, tenderness to pressure, rash, swelling, fever, or restricted movement.
Based on your history and physical examination, you might need one or more of the following:
Blood tests: Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) signal generalized inflammation. High levels of uric acid are often seen in gout. Elevated anti-cyclic citrullinated peptide (CCP) or the presence of rheumatoid factor (RF) is often seen in rheumatoid arthritis. However, high uric acid does not always mean a swollen joint is due to gout, and RF can be seen in diseases other than RA.
Imaging tests: Ultrasound, X-ray, computed tomography (CT), and magnetic resonance imaging (MRI) can help visualize bone or soft tissue damage, including dislocation, hemorrhage, or effusion (accumulation of fluids).
Joint aspiration: Arthrocentesis is the removal of fluid with a needle from the joint space for evaluation in the lab. Arthrocentesis is generally indicated if the symptoms are severe and an infection is suspected, especially with preexisting arthritis.10
Blood and tissue cultures: The bacterial or fungal organisms causing an infection can be grown and identified in a lab.
Antinuclear antibody (ANA) tests: Specific proteins, known as autoantibodies, which are associated with an autoimmune process, can be detected in the blood.
Differentiating the possible causes of joint warmth may take time, but there are clues that can often help. These include how many joints are affected, whether the joint pain is bilateral or unilateral (differentiating rheumatoid arthritis from osteoarthritis), whether the event is recurrent or isolated, or whether the symptoms are limited to the joint or more constitutional (systemic).11
The treatment of a joint condition is ultimately directed by the diagnosed cause. The options can be broadly described based on whether the cause is traumatic, infectious, or rheumatic.
Mild joint injuries may only require rest, restriction of movement, ice application, and non-steroidal anti-inflammatory drugs (NSAIDs). More serious injuries may require complete joint immobilization.
Surgery may be indicated if a bone is fractured or there are ruptured tendons or ligaments that cannot heal on their own.
Bacterial joint infections are usually treated with a combination of intravenous antibiotics and a procedure to clean out the joint, either with surgery or repeated extractions of joint fluid (arthrocentesis). Bacterial cultures of the joint fluid and/or blood can help direct antibiotic selection.
Fungal infections, more commonly seen with a compromised immune system, are treated with oral or intravenous (IV, in a vein) antifungals.
Osteoarthritis is managed with sparing use of pain medications, along with physical therapy, exercise, weight loss, and ice or heat application. Oral or injected corticosteroids, intra-articular hyaluronic injections, arthroscopic surgery, and joint replacement may be considered if the disease progresses.
Rheumatoid arthritis and other autoimmune joint disorders may be treated in a similar manner but may also be brought under control with disease-modifying antirheumatic drugs (DMARDs) and other biologic and targeted treatments that help control the immune response.