What’s Causing My Knee Pain?

Medically Reviewed by Jabeen Begum, MD on March 18, 2024
8 min read

Being active is one of the best things you can do for your joints and the rest of your body. But injuries can happen, and they often involve the knees.

Your knee pain might start suddenly, or it could build up from mild discomfort to more painful over time. It can be caused by injury, overuse, aging, arthritis, or a variety of other medical conditions.

Some of the most common problems are sprained ligaments, meniscus tears, tendinitis, and runner's knee. If you have an old knee injury that wasn’t properly treated, it may flare up now and then or hurt all the time.

Many different types of injuries can cause knee pain. These include strains, sprains, ligament tears (such as ACL injury), cartilage tears, or broken bones (called a fracture). They can happen from landing wrong on your foot, falling, twisting the knee, or impact injuries, such as being hit on the knee. Swelling around the injury is the main cause of pain.

Aging, being overweight, and intense repetitive exercise can all cause knee pain. 

Overuse injuries. These can happen over time from doing activities like running, jumping, or other exercises that put repeated pressure on the knee. This is sometimes called “runner’s knee.” 

Patellar tendinitis. This means you have inflammation in the tendon that connects the kneecap to the shinbone. Tendons are tough bands of tissue that connect muscles to bones. When you overdo exercise, they can become inflamed and sore. You may also hear it called “jumper’s knee” because repetitive jumping, such as from basketball, is the most common cause.

IT (iliotibial) band syndrome. The iliotibial (IT) band is a piece of tough tissue that runs from your hip down to the outer part of your knee. When you overdo activity, it can become inflamed over time. That causes pain on the outer side of the knee. It’s common among runners, especially when going downhill.

Old injuries. When your previous injury didn’t heal well, it can also cause pain later in life.

Aging. As you get older, the bones and joints of the hip, knee, and foot begin to degenerate, making them weaker. This can lead to knee pain, swelling, and injury.

Being overweight or obese. Having a larger body size puts extra pressure on the knees. This can cause swelling and pain.

Baker’s cyst. This is a fluid-filled lump that develops at the back of the knee. It can happen after an injury to the knee or if you have arthritis. The cyst may cause pain and swelling.

Swelling and tenderness of the joints is called arthritis. It is a common cause of knee pain and joint stiffness. There are several types. 

Osteoarthritis. This is the “wear and tear” type of arthritis that breaks down the cartilage in the knee. It’s a top cause of knee pain after age 50. This condition causes the knee joint to ache or swell when you’re active. Joints affected by osteoarthritis can also be stiff early in the day.

Gout. This condition, which is caused by a buildup of uric acid in the blood, is a type of inflammatory arthritis. It causes sudden, intense bouts of pain in the joints along with swelling, redness, tenderness, and heat. 

Lupus. This long-lasting immune system condition can cause inflammation and pain in the knee joints. This is also a form of inflammatory arthritis, which is a condition that occurs when you have an overactive immune system that causes joint pain.

Rheumatoid arthritis. Rheumatoid arthritis is an autoimmune disease condition where the healthy tissue in your joints, like your knees, is attacked by your immune system. The cartilage in your knee can be worn down over time by affected cells,  causing swelling, stiffness, and pain. 

Other health issues can also cause knee pain, including:

Bursitis. A bursa is a sac that holds a small amount of fluid that’s under the skin above your joint. It helps prevent friction when the joint moves. Overuse, falls, or repeated bending and kneeling can irritate the bursa on top of your kneecap. That leads to pain and swelling. Doctors call this prepatellar bursitis. You may also hear it called ''preacher's knee."

Dislocated kneecap. This means that your kneecap slides out of position, causing knee pain and swelling. Your doctor may call this “patellar dislocation.”

Meniscal tear. Sometimes, a knee injury can cause cartilage to rip. These rough edges can get stuck in the joint, which causes pain and swelling. Many times, people will have the sensation of “catching” in the joint when they are active.

Osgood-Schlatter disease. This condition happens when you’re young when bones and other parts of the knee are still changing. It can cause a painful bump below the knee, where a tendon from the kneecap connects to the shin. Overdoing exercise, and irritation at a point on the bottom of your knee called the tibial tubercle, often make this area hurt. The ache may come and go over time. It's especially common in teenage boys and girls.

Patellofemoral pain syndrome. Muscle imbalance, tightness, and alignment problems of the legs usually cause this condition. It causes knee pain and occasional “buckling,” meaning your knee suddenly can’t bear your weight. It’s not due to an injury. It's more common for women than for men.

 If you or someone you’re with has a knee injury, call 911 or go to urgent care or the emergency room if: 

  • The knee or leg bones look deformed.
  • The person can't put weight on the leg.
  • The pain is extreme.
  • There is immediate swelling, tingling, or numbness below the knee.
  • You heard a popping sound when the knee was hurt.

Obviously, it hurts! But the type of pain and where you feel it can vary, depending on what the problem is. You may have:

  • Pain, usually when you bend or straighten the knee (including when you go down stairs)
  • Swelling
  • Trouble putting weight on the knee
  • Problems moving your knee
  • Knee buckling or “locking”

If you have these symptoms, see your doctor. They will check your knee. You may also need X-rays or a test called an MRI (magnetic resonance imaging) to see more detail of the joint.

Your plan will depend on your specific injury. Mild to moderate issues will often get better on their own. To speed the healing, you can:

Rest your knee. Take a few days off from intense activity.

Ice it to curb pain and swelling. Do it for 15 to 20 minutes every 3 to 4 hours. Keep doing it for 2 to 3 days or until the pain is gone.

Compress your knee. Use an elastic bandage, straps, or sleeves to wrap the joint. It will keep down swelling or add support.

Elevate your knee with a pillow under your heel when you're sitting or lying down to cut down on swelling.

Take anti-inflammatory medications. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or naproxen will help with pain and swelling. Follow the instructions on the label. These drugs can have side effects, so you should only use them now and then unless your doctor says otherwise.

Practice stretching and strengthening exercises if your doctor recommends them. You may want to do physical therapy, too.

Make an appointment with a doctor if you still have pain after 2 weeks of home treatment, if the knee becomes warm, or if you have fever along with a painful, swollen knee.

Some people with knee pain need more help. For instance, if you have bursitis, your doctor may need to remove extra fluid from the bursa in your knee. If you have arthritis, you may need an occasional corticosteroid shot to settle down inflammation. And if you have a torn ligament or certain knee injuries, you may need surgery.

The recovery time depends on your injury. Also, some people naturally heal faster than others.

While you get better, ask your doctor if you can do an activity that won't aggravate your knee pain. For instance, runners could try swimming or other types of lower-impact cardio. Some light physical activity may even help reduce pain.

Whatever you do, don't rush things. Slowly increase intensity and how long you exercise. Don’t try to return to your regular level of physical activity until you notice these signs:

  • You feel no pain in your knee when you bend or straighten it.
  • You feel no pain in your knee when you walk, jog, sprint, or jump.
  • Your injured knee feels as strong as the other knee.

Although you can’t prevent all injuries, you can take these steps to make them less likely.

  • Stop exercising if you feel pain in your knee.
  • If you want to make your workout more intense, always do it gradually.
  • Stretch your legs before and after physical activity.
  • Use kneepads to prevent bursitis, especially if you have to kneel a lot.
  • Wear shoes that fit well and offer enough support.
  • Keep your thigh muscles strong with regular stretching and strengthening.
  • If you have obesity, talk to your doctor about getting to a healthy weight so there’s less stress on all of your joints, including your knees.
  • Get regular physical activity, such as walking, strength training, yoga, cycling, or swimming.
  • Choose low-impact exercises that don’t require jumping.


Knee pain is caused by injury and a variety of medical conditions. Fixing your knee pain starts with figuring out what is causing it and then following the right treatment plan. Contact your doctor if home care doesn’t provide relief -- or right away if you’re in intense pain, it’s getting in the way of your day-to-day activities, or you have any questions or concerns.

What can cause knee pain without injury?

Knee pain without injury can be caused by overuse, arthritis, past injury, infection, bursitis, knee tendinitis, cancer, being overweight, Osgood-Schlatter disease, Baker’s cyst, injections in the knee joint, or problems with your hip, foot, or ankle.

How do I fix my knee pain?

It depends on what is causing your knee pain. However, fixing your pain may include a combination of rest, icing, heat, compression (wrapping the knee), elevating the leg, light physical activity, and strengthening the muscles around the knee. You also may need medication, physical therapy, or surgery.

How do I know if my knee pain is serious?

Knee pain is serious if you can’t bear weight on the knee, it causes severe pain, you hear a popping sound when it starts hurting, it looks deformed, or it swells suddenly. If you have any of these symptoms, contact your doctor and/or seek medical care right away. Also, see your doctor if you have knee pain along with a fever, it’s hard to walk, or if your knee is red, very swollen, hot, or painful.