By Eric Metcalf, MPH | Medically reviewed by Pat F. Bass III, MD, MPH for everydayhealth.com
Because the knee has many parts that can be damaged, there are many causes of knee pain. Learn about common injuries and conditions.
Although it’s a fairly small part of the body, a lot can go wrong with your knee. Here’s an overview of just some of the conditions that commonly cause knee pain.
Arthritis: One of the most common causes of knee pain that doctors see is arthritis, says Jonathan Shook, MD, an orthopedic surgeon in Indianapolis. There are several types of arthritis than can cause knee pain:
Osteoarthritis causes the smooth, protective layers of cartilage in the knee to become worn, leading to damage in the bones in the knee.
Rheumatoid arthritis affects the knee after the body’s immune system attacks a membrane within the joint, causing pain, inflammation, and damage to tissues in the knee.
Gout occurs when a substance called uric acid gathers in the knee, causing sharp pain.
Pseudogout can strike the knees after crystals of calcium pyrophosphate build up in the joints.
Septic arthritis, in which bacteria attack the joint, causes severe pain, swelling, and stiffness.
Post-traumatic arthritis develops years after you have an injury in your knee, such as a fractured bone or a damaged ligament.
Meniscal injury: Another common condition that triggers knee pain involves your meniscus, Dr. Shook says. This is a structure in the knee providing cushioning that tends to suffer wear and tear over your life. He often sees young, active patients who have suddenly gotten a meniscal tear in a sporting event, and older patients who develop a more chronic tear in a worn meniscus.
Osgood-Schlatter disease: Typically affecting obese, active adolescent boys, this condition is caused by tendons attached to the upper shin bone in the knee. During certain movements, the tendons pull away from the bone, triggering knee pain.
Bursitis: Several fluid-filled structures in your knee called bursas help provide more cushioning in the joint. Certain activities, such as kneeling on the floor, can cause a bursa to become irritated, a condition called bursitis.
Tendinitis: Tendons are strong tissues that anchor muscles to bones, and they can become torn or inflamed, a condition called tendinitis.
Ligament injuries: Ligaments are another kind of tissue that helps hold the knee together. You have ligaments that connect bones in the knee along the inside and outside edges (the collateral ligaments), and two that criss-cross within the knee (the cruciate ligaments). These ligaments can become over-stretched or torn, often during sporting or athletic activities. Depending on the ligament, this may cause varying degrees of knee pain, and your knee may become wobbly after the ligament injury.
Chondromalacia patellae: In this condition, cartilage under the kneecap weakens and breaks down. It can be caused by overuse of the knee, injuries to the joint, or having a kneecap that’s not properly in line. The damage to the cartilage can be mild or severe.
Patellofemoral pain syndrome: Also called “runner’s knee,” this is a common cause of knee pain. It can be caused by overdoing physical activities, tissues around your knee that are too tight or too weak, and misalignment of your kneecap.
Knee dislocation: Another condition that can cause knee pain is when your kneecap becomes dislocated. Instead of resting in its normal location in a notch at the bottom of your thigh bone, it moves to the side — typically toward the outside edge of your knee. This often occurs when a person is bearing the full body weight on one foot and twists or changes directions quickly.
Knee injuries are very common and can be quite painful. If you have knee pain, see your doctor to find out which condition may be the source of your pain.
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