Written by Frank Schwalbe, MD | Reviewed by Karla Robinson, MD
Key takeaways:
Knee cracking, popping, and clicking can be completely harmless. But in some cases, it may be the signs of an underlying condition affecting the knee joint.
Meniscal tears, cartilage injuries, and osteoarthritis are common causes of popping and cracking knees.
If you have knee popping and cracking along with other symptoms like swelling, pain, or trouble moving your knee, seek medical care.
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Your knees have a big job to do. They’re responsible for bearing your weight when you walk and move around. Because of their constant use, knees can be prone to injury and wear and tear. If your knees are making noise, they might be trying to tell you something.
Sometimes, your knees will let you know they aren’t in peak condition by sending you signals in the form of pops, cracks, and clicks. But what do these sounds mean? And why do they happen? Let’s take a closer look at popping and cracking knees and what to do about them.
What causes knee cracking, popping, and clicking?
Any time one part of the knee moves across another, there’s a potential for it to make noise. This is known as crepitus. This can happen with healthy bones, tendons, and ligaments. But it’s even more likely to happen when your knee suffers an acute injury. Grinding, cracking, or popping is also possible with chronic knee conditions where damaged tissues rub together often.
Let’s take a look at six of the most common causes of knee cracking and popping.
Normal movement
It’s possible for a normal, healthy knee joint to make noise. Because everyone’s knee is a little different, some people can have cracking or clicking joints while others don’t.
Your healthcare provider can tell if the sound is concerning by taking your history and doing a physical exam. They’ll ask questions like: How long have you heard the noise? Does it hurt? And while checking you, they’ll make sure the knee has a normal range of motion.
Most people can’t recall when they first noticed noise in a normal knee. It’s always painless, with a normal range of motion.
Meniscus injury
The meniscus is a piece of fibrocartilage on either side of the knee joint. Its job is to add a layer of cushion where the bones of the knee joint come together. When a meniscus is torn, it blocks the normal bending of the knee. As the torn meniscus gets caught in the joint, it can cause a popping or clicking sound.
Meniscal tears can happen suddenly during physical activity. They can also happen gradually, over time. The amount of pain and clicking can vary depending on how bad the tear is and where it’s located.
Cartilage injury
Cartilage is a type of tissue that covers the moving surfaces of the knee bones. It helps the joint move smoothly. Cartilage injuries are common. The degree of pain and clicking due to a cartilage injury can vary. A small cartilage injury may have no symptoms at all. A larger injury can cause loud popping and disabling pain.
Other symptoms of a knee cartilage injury can include:
Swelling
Limping
Locking or “catching” feeling in the knee
Knee instability
Acute cartilage injuries are more likely to happen in younger, physically active people.
Osteoarthritis
Osteoarthritis is the most common inflammatory condition of the knee. It’s a chronic (long-term) condition that develops over time. Osteoarthritis happens when the cartilage lining the knee joint wears away, leaving exposed bones to rub against each other. This damages the joint, causing an inflammatory response.
Osteoarthritis can cause abnormal noises when bending the knee, like popping, grinding, or cracking. It can also cause swelling and pain. Osteoarthritis is more likely to affect older or heavier adults.
Kneecap instability
The knee cap (patella) is held in place in front of the knee joint by a large ligament. Sometimes, the patella pops out of its normal place, leaving the knee joint unstable and prone to injury. A lot of things can weaken the patellar ligament, including:
Acute injury
A chronically loose ligament
Bone misalignment
Connective tissue disorder (like Ehlers-Danlos syndromes)
Structural problems
In addition to knee popping and cracking, this can cause chronic pain and lead to osteoarthritis over time.
Patellofemoral pain syndrome (PFPS)
Patellofemoral pain syndrome (PFPS) is the most common cause of knee pain in adolescents and adults under 60 years old. You may have a clicking sound with pain in the front part of the knee with bending, squats, or going down stairs.
About 5% of adults and adolescents experience PFPS. The exact cause is not clear, but it is more common in:
Women
People who have weaker strength in their quadriceps (thigh muscle)
Runners (runner’s knee)
People with a foot or heel abnormality (like clubfoot)
People with a sudden increase in physical activity
Is knee cracking serious?
Knee cracking is not always serious. In fact, some sounds coming from your knee may be completely harmless. If your knees have cracked for ages, but they don’t hurt, it’s probably nothing to worry about.
Knee cracking that comes on suddenly, especially after some type of injury or trauma, is more likely to be serious. This is especially true if you also have pain or swelling. If you have trouble with moving or bearing weight on the knee, this may be a sign that you may have a serious underlying issue.
When should you seek treatment for knee cracking?
If you notice a sudden change in your knee along with increased noises, it’s best to seek medical care to figure out the cause. Some of the reasons that should prompt you to visit your provider for knee cracking include:
Pain
Swelling
Redness or warmth of the knee joint
Inability to bear weight
Limited range of motion
History of an injury
The knee feels unstable
Deformity of the knee joint
How can you fix knee cracking?
The treatment for cracking knee joints also depends on the cause. If it’s not causing any pain or discomfort, there’s often nothing you have to do. Frequently, rest, ice, and over-the-counter (OTC) pain relievers will do the trick if there is minor inflammation or pain. Your provider may also recommend exercises to strengthen your knees. But for more serious injuries that don’t heal on their own, medical treatment may be necessary.
For serious knee conditions or injuries that need repair, your healthcare provider may recommend arthroscopic surgery. Arthroscopic surgery allows the surgeon to repair the knee joint by placing small instruments and a camera through tiny incisions in the knee.
Sometimes, more invasive surgery may be necessary if the problem can’t be corrected with arthroscopy. Occasionally, a total knee replacement may be the only remedy for severe conditions such as osteoarthritis or severe trauma.
The bottom line
Popping, cracking, and grinding sounds in the knees are common reasons for people to seek medical care. In some cases, it can be normal and there’s nothing to worry about. But if you have other symptoms such as pain, swelling, redness, or trouble moving your knee, this could be the sign of a serious knee joint problem. Talk to your healthcare provider if you have concerns about a popping or cracking knee. They can figure out what’s causing your symptoms and advise you on any next steps to take.
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