When the knee gets hot after exercising, it could indicate a variety of problems. The increased temperature is often a sign of inflammation -- the body's response to tissue injury or infection. Underlying disorders that cause inflammation -- like osteoarthritis, rheumatoid arthritis and gout -- can lead to a hot knee after exercise. Other potential causes include overuse injuries, along with damage to ligaments, tendons and knee cartilage. Treatments vary depending on the cause.
When the knee feels hot after exercising, it is a sign of increased blood flow to the joint. The vessels transport warmer blood from the center of the body to the knee joint. Heat, swelling, pain and redness are the 4 key signs of inflammation. The body’s inflammatory response is designed to heal injured tissue and fight infections. However, continuous inflammation can lead to tissue destruction and joint damage. It is important to determine the cause of inflammation so it can be treated appropriately to prevent further damage.
Medical Causes of Knee Inflammation
Many conditions can cause the knee to feel hot after exercise. A common offender is arthritis. Arthritis is characterized by joint inflammation that damages cartilage -- the smooth surface between bones that allows the knee to move easily. Typical forms include osteoarthritis, rheumatoid arthritis and gout. Osteoarthritis is associated with aging. It may also develop years after a traumatic knee injury or in overweight individuals. Rheumatoid arthritis is an autoimmune disease in which the body attacks the joints. Uric acid can accumulate in the joint and cause inflammation, resulting in the condition called gout.
Injuries Causing Knee Inflammation
The knee may become hot after exercise due to underlying injuries, including tears of the tendons, ligaments and menisci -- special types of cartilage that act as shock absorbers within the knee. Damage to these structures may cause catching or popping in the joint and affect overall knee stability. When joints become less stable, abnormal stress occurs, leading to damage and swelling. A hot knee after exercise may also occur in a person who has an overuse injury, such as bursitis -- inflammation of the bursa, which is a fluid-filled sac that cushions the places where muscles, tendons and ligaments rub over bones. Patellofemoral syndrome -- softening of the cartilage under the kneecap -- is another overuse injury that can cause a hot knee.
General treatments that reduce heat in the knee joint and decrease inflammation include rest, wrapping the joint, applying ice and elevating it above the level of your heart. Determining the reason for a hot knee after exercise is essential, given the variety of treatable causes. Seek medical attention if you have knee stiffness, if you feel or hear popping or catching in the knee, or if you experience difficulty walking or numbness or weakness in the knee area. Also see your doctor if you have a fever, rash, swelling or redness of the knee or other joints.
- International Orthopaedics: The Fate of Acutely Inflamed Joints With a Negative Synovial Fluid Culture
- Canadian Family Physician: Exercise and Knee Osteoarthritis: Benefit or Hazard?
- National Institute of Arthritis and Musculoskeletal and Skin Diseases: Knee Problems
- Merck Manual: Professional Edition: Gout