Knee popping is often harmless and may occur when a person exercises. However, when it occurs alongside pain, it may be a sign of an underlying problem, such as arthritis or a knee injury.

With a knee injury, the popping sound may be sudden, with pain and swelling afterward. In other cases, popping and pain may be chronic or ongoing.

This article examines the causes of knee popping and pain, as well as when to consult a doctor and seek treatment. It also looks at risk factors, tips for healthy knees, and the outlook for people with knee popping.

A person stretching on a yoga mat in an outdoor court.Share on Pinterest
Ivan Ozerov/Stocksy

Knee popping, on its own, is usually harmless. It is very common and often occurs for physiological reasons rather than because of a medical condition, according to a 2018 study.

This means knee popping, clicking, and creaking often occur because of the knee’s anatomy.

The kneecap sits in a curve in the thighbone called the trochlea. When the knee straightens or bends, the kneecap moves backward and forward inside the trochlea. The trochlea is padded by soft tissue for protection.

People may notice popping in this area when they do certain exercises, such as squats. This is fairly typical, and not necessarily a sign anything is wrong.

However, if pain or swelling occurs alongside the popping, this is known as pathological noise and could indicate an underlying problem.

Some causes of ongoing knee popping and pain include:

  • Arthritis: Osteoarthritis (OA) occurs when the soft tissue inside joints wears down over time. This can affect the smooth motion of the knee, causing creaking, scraping, or popping noises alongside pain. People with OA may feel the pain only during exercise or after resting or sleeping.
  • Patellofemoral syndrome (PFS): PFS, or runner’s knee, can occur when the kneecap does not track along the trochlea correctly or when the joint undergoes too much stress. People with runner’s knee may experience a grinding, popping, or catching sensation at the kneecap when bending or straightening the leg, either around or behind the knee.
  • Cartilage damage: Damaged cartilage can cause popping noises as the knee moves and can cause inflammation, limited range of motion, and swelling.
  • Surgery: Knee surgeries can sometimes result in ongoing complications, such as popping or pain.
  • Avascular necrosis: This condition causes the death of bone tissue due to a lack of blood supply. Other symptoms of avascular necrosis include pain and limited range of motion.

Potential causes of sudden knee popping and pain include:

  • Ligament tear: Anterior cruciate ligament (ACL) tears are the most common type of knee injury. They cause a loud popping noise, typically followed by severe pain and significant swelling. A person may not be able to stand on the affected leg. Injuries and tears can also affect other knee ligaments.
  • Torn meniscus: The meniscus is a tough piece of tissue between the thigh and shin bone. The meniscus can tear if someone suddenly rotates or bends the knee with significant force. The injury can cause pain, stiffness, swelling, a catching or locking sensation, or the knee giving way.
  • Patellar tendon tear: The patellar tendon joins the top of the kneecap and shinbone. A torn patellar tendon can cause a popping or tearing sensation, pain, bruising, difficulty straightening the leg, and an indentation at the bottom of the kneecap.

Learn more about patellar tendonitis.

A person should contact a doctor about a knee popping and pain if they:

  • may have injured the knee
  • experience swelling or discoloration
  • cannot move the knee through its full range of motion
  • cannot put weight on the knee
  • cannot relieve the pain with over-the-counter pain medications
  • have difficulty exercising or carrying out daily activities

The treatment of knee popping and pain will differ according to the cause of the pain and the severity of the symptoms.

For ongoing conditions, such as arthritis or PFS, the treatment may include:

To keep the knees healthy, the Arthritis Foundation recommends:

  • Exercise: Regular exercise can help keep the muscles around the knees strong and improve balance, which reduces the risk of falls and injuries. People may benefit from low impact cardio, strengthening exercises, and activities that improve flexibility.
  • Weight management: A higher body weight increases pressure on the knee joints, which contributes to wear and tear. Maintaining a moderate weight can help reduce this.
  • Protection against injury: Certain activities, such as high impact sports, put repeated stress on the knees and are more likely to cause injury. Taking steps to reduce this risk and treating injuries promptly if they occur is important for long-term knee health.
  • Quit smoking or vaping: People who smoke or vape are more likely to develop arthritis, including inflammatory forms of arthritis.
  • Eat a balanced diet: Anti-inflammatory diets, such as the Mediterranean diet, may reduce OA symptoms. Certain nutrients such as calcium are also important for strong, healthy bones and joints.
  • Wear supportive shoes: Misalignment in the feet can have a knock-on effect on the knees. For example, high heels increase stress on the knee joints. Choose flexible shoes with room for the toes and minimal or no heels.

Many people experience popping sensations and sounds in their knees. Usually, this is not a cause for concern. However, a person may require medical attention when pain or swelling accompanies the popping sound.

Frequent knee popping and pain may be an early sign of arthritis, the result of cartilage damage, runner’s knee, or complications from surgery. Sudden knee popping followed by pain usually indicates an injury.

Treatment for these symptoms will depend on the cause.