11 Potential Causes of Knee Pain

Experiencing mild knee pain or discomfort after a workout is common, but if it becomes persistent, it could be a more serious problem. There are several potential causes, including ligament tears, osteoarthritis, and runner’s knee. The course of treatment will depend on your diagnosis.

The knee is a complex joint involving bones, ligaments, menisci, muscles, and tendons that all support the joint. You may have achy knees if there is damage or stress to any of those components. Many physical activities, such as bending, jumping, running, and stretching, can impact or strain your knees, which may cause pain while you work out.

Knee pain is a common exercise complaint, affecting about 25% of adults. Read on to learn about the common causes of knee pain and how to treat it.

Bursitis

Bursitis causes pain in the front of your knee if a bursa becomes irritated and swollen. A bursa is a fluid-filled sac that cushions and protects your bones, muscles, and tendons.

Inflammation may occur due to injury, overuse, or repeated pressure, such as kneeling. Changes in activity level (e.g., training for a marathon), infections, and some types of arthritis may cause bursitis.

Bursitis symptoms include:

• Pain and tenderness when you press on your knee
• Pain around your knee
• Pain while moving and resting
• Redness, swelling, or warmth
• Stiffness while moving

Iliotibial Band Friction Syndrome

Overuse causes iliotibial band friction syndrome (ITBFS), a knee joint injury. ITBFS occurs when your iliotibial (IT) band, a tendon along the outside of your leg, rubs against the bone, typically when you bend. As a result, your IT band becomes irritated and swollen. You may feel pain in your lateral (outer) knee.

ITBFS commonly affects 1.6% to 12% of athletes like:

• Basketball, hockey, or soccer players
• Cyclists
• Long-distance runners
• Skiers

You might develop ITBFS if you do not warm up before exercising. ITBFS symptoms first appear when you start exercising and get better after you warm up. As ITBFS progresses, you may feel pain after warming up. Bending your knee while sitting or running down a hill worsens pain.

Jumper’s Knee

Jumper’s knee—also called patellar tendinitis, patellar tendonitis, or patellar tendinopathy—is a knee joint injury. As the name suggests, you can develop jumper’s knee after strenuous jumping, often from playing basketball or volleyball. Long-distance running and skiing may result in jumper’s knee.

Jumper’s knee primarily affects athletes aged 15–30.6 People with jumper’s knee typically have pain below their kneecap and stiff knees while climbing stairs, jumping, and kneeling. Resting is usually painless.

Ligament Tears

Ligaments are tissues that connect bones. The anterior cruciate ligament (ACL) and medial collateral ligament (MCL) can tear and cause instability, pain, and swelling. The ACL runs in the middle of your knees. The MCL, located on your inner knees, prevents them from bending inward. The ACL and MCL are the two most commonly injured ligaments of the knee, though you can also tear your posterior cruciate ligament (PCL) or lateral collateral ligament (LCL).

Symptoms of ligament tears in the knee include:

• A loud popping sound at the time of injury
• Feeling unstable (e.g., your knees may shit from side to side if you have an MCL tear)
• Pain
• Swelling, typically within six hours of an ACL injury

ACL and MCL injuries typically occur among basketball, football, soccer, and skiing athletes. You may tear your ACL or MCL if you get hit during a tackle, overextend your joint, and quickly stop moving and change directions.