What Causes Knee Pain After Working Out?

Knee pain from exercise? Here are some causes—and what to do about them.

Knee pain is a common exercise complaint—about 25% of adults experience it. Many physical activities—including running, jumping, stretching, and bending—can place a strain or impact directly on the knees, and in turn, cause pain while you work out.

The knee is an intricate joint, involving bones, menisci, muscles, tendons, and ligaments that all support the joint. You may have achy knees if there is damage or stress to any of those components.

Here's what you should know about the common causes of knee pain.

Tired woman in exercise clothes touching knee in pain

Panuwat Dangsungnoen / EyeEm/Getty Images

Runner's Knee

Runner's knee, also called patellofemoral pain syndrome (PFPS), is a type of injury to the knee joint. It's the most common type of injury caused by musculoskeletal overuse. About 13% to 30% of runners experience runner's knee. Additionally, people can develop the condition from trauma or surgery in the area.

Runner's knee is one of the most common causes of pain in the front of the knee. People also describe the feeling as a tender or grating sensation. The pain can worsen after sitting for a while, getting up from a chair, squatting, running, or using the stairs.

People often experience runner's knee when they change running mileage or speed or start completing more hill training than normal. Stress, as well as poor nutrition and sleep, can contribute to the injury.

People generally recover from runner's knee, but it may take a while. About 40% of people still experience symptoms after one year of treatment, which includes modifying workouts, using nonsteroidal anti-inflammatory (NSAID) drugs to relieve pain, icing the area, exercising the knee and hip, and taping the knee.

Iliotibial Band Friction Syndrome

Iliotibial Band Friction Syndrome (ITBFS) is another type of knee joint injury caused by overuse. Long-distance runners, cyclists, skiers, and hockey, basketball, or soccer players commonly experience the condition. About 1.6% to 12% of those athletes can experience ITBFS.

People feel ITBFS pain in their knees' outer (lateral) part. It occurs when the iliotibial band—a tendon along the outside of your leg—becomes swollen and irritated by rubbing against the bone, typically when you bend. You can develop ITBFS if you don't warm up before exercising.

ITBFS symptoms first appear when you start exercising and get better after you warm up. As the condition progresses, you may feel pain after warming up. Bending the knee while sitting or running down a hill worsens pain.

Jumper's Knee

Jumper's knee—also called patellar tendinopathy, patellar tendinitis, or patellar tendonitis—is a knee joint injury that primarily affects athletes between ages 15 to 30 years. As the name suggests, you can develop jumper's knee after strenuous jumping, often from participating in volleyball, track, and basketball. Long-distance running and skiing can also result in jumper's knee.

People with jumper's knee typically experience pain below the kneecap and knee stiffness while jumping, kneeling, or climbing stairs. Resting is typically painless.


Knee osteoarthritis (OA) occurs when wear and tear break down joint cartilage (called connective tissue). It's one of the most common diseases affecting the knee and can happen due to injury or overuse.

People typically develop OA as they age. About 3% of people between the ages of 45 to 54 years experience OA, compared to 44% of people aged 80 years or older.

Knee pain from OA typically gets worse due to the following:

  • Moving around for long periods of time
  • Repetitive bending
  • Using stairs
  • Inactivity
  • The longer you've had the condition

Knee swelling, stiffness, and changes that limit motion can also occur. You may hear a grinding or scraping noise when walking and experience buckling knees.

If you're worried that you might have knee OA, schedule an appointment or ask your healthcare provider for a referral to a rheumatologist, a healthcare provider specializing in arthritis and other joint conditions.

Your rheumatologist may also diagnose you with knee pain from a different type of arthritis, such as rheumatoid arthritis, osteoarthritis, lupus, or gout. But OA is one of the most common types of arthritis, which is the general name for a condition that causes deterioration or inflammation in the joints.


A bursa is a sac, filled with fluid, that cushions and providers protection to your muscles, tendons, and bones. In bursitis, a bursa becomes swollen and irritated, and you may feel pain in the front of your knee.

The inflammation may occur because of overuse, injury, or repeated pressure—for example, from kneeling. Changes in activity level, such as training for a marathon, may also cause bursitis, as well as infection or some types of arthritis.

Symptoms of bursitis include:

  • Pain and tenderness when you press on the knee
  • Stiffness when moving
  • Pain when moving and resting
  • Swelling, warmth, or redness
  • Pain in areas near the knee

Ligament and Cartilage Tears

Ligaments are tissues that connect bones to each other. Two ligaments—the anterior cruciate ligament (ACL) injury and medial collateral ligament (MCL)—can tear and cause knee pain, swelling, and instability.

The ACL runs in the middle of the knee. An ACL injury typically occurs among athletes who play basketball, football, soccer, and skiing. You may tear your ACL if you get hit during a tackle, overextend your joint, or quickly stop moving and change direction.

The MCL is on the knee's inside, preventing it from bending inward. The same sports that are associated with ACL injuries can also tear your MCL.

Symptoms of ligament tears in the knee include:

  • A loud popping sound at the time of injury
  • Swelling—within six hours in the case of an ACL tear
  • Pain
  • Feeling unstable—your knee may also shift from side to side in the case of an MCL tear

The meniscus is a "cushion" between the ends of bones in a joint and absorbs shock. It can tear if you twist your knee, kneel, or squat while lifting something heavy. You may also tear it the same way as an ACL: quickly stopping moving and changing direction or getting hit.

Symptoms of meniscus tears, which often occur with ACL and MCL tears, include:

  • Pain that gets worse if you put pressure on the knee or walk
  • Swelling the day after the injury
  • Locking of the knee

Strains or Sprains

Strains are muscle tears, also called pulled muscles, caused by excessive physical activity, improper warmups before exercise, and poor flexibility.

Sprains are ligament injuries that can occur from tears or excessive stretching. Both strains and sprains are caused by abrupt and unnatural twisting of muscles.

Common symptoms of the two injuries include:

  • Pain
  • Swelling
  • Joint stiffness in sprains and difficulty moving the muscle
  • Discoloration or bruising of the skin

Both strains and sprains are considered minor injuries. Warming up properly before exercise can help prevent them.


Home care is the first step to treating knee pain that is not severe. Try the following techniques to relieve knee pain:

  • Rest.
  • Apply ice.
  • Keep your knee raised.
  • Wear an elastic bandage or elastic sleeve.
  • Take over-the-counter (OTC) pain relievers, like NSAIDs, but talk to your healthcare provider if you take them for more than two days.

After the symptoms subside, talk to your healthcare provider about customizing a physical therapy program to treat your condition.

For example, people who experience runner's knee benefit from hamstring stretching, quadriceps strengthening, and hip exercises. And for jumper's knee, eccentric exercise—a type of exercise that causes your muscles to lengthen—is most effective.

Cardio exercises may help with arthritis. Your healthcare provider can also prescribe braces or custom-molded shoe inserts.

When to See a Healthcare Provider

Occasionally, you may experience a serious knee condition, such as a kneecap fracture or dislocation and bone fracture. If you experience severe pain, it's always a good idea to see a healthcare provider.

Here are some other signs that you should discuss with your healthcare provider:

  • Buckling, clicking, or locking
  • Deformity or other change in shape
  • Trouble flexing or straightening your knee
  • Fever, redness, or warmth that accompanies swelling
  • Pain after three days of at-home treatment

Treatments for severe knee pain vary. For some conditions, your healthcare provider may give you a steroid injection to reduce pain and swelling. In many cases, they will refer you to a physical therapist. And occasionally, depending on your injury, you may require surgery.

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