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Understanding Knee Clicks and Cracks: How to React, When to Worry

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Last updated April 16, 2024

Knee clicking quiz

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Fortunately, your talkative knees are usually not a cause for concern. But when those clicks, pops, and cracks occur regularly, it may be time for consultation.

Knee clicking quiz

Take a quiz to find out what's causing your knee clicking.

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Those odd sounds you seem to be hearing in your knees, known as crepitus, can occur during everyday activities — walking, stretching, bending, extending, or straightening your knee. Crepitus is fairly common; many people experience these knee clicks at some point in their lives. Exercises that strengthen muscles around the knee (such as side steps with a resistance band, hip flexor or calf strengthening moves, or inner thigh squats) can often quiet knee sounds. Fortunately, those talkative knees are usually not a cause for concern. But when those clicks, pops, and cracks occur regularly and are accompanied by pain and or swelling, it’s time for you to talk back to your knees by taking them to a conversation with your doctor.

There are a number of things that can cause knee clicking, with or without pain. Here are some of the most common causes of knee clicks and cracks.

Gas bubbles

The knee joint acts like a large hinge; synovial fluid fills the surrounding area and acts as a lubricant to help the knee joint perform well. Sometimes, however, gas bubbles can form in the synovial fluid. A clicking or popping sound occurs whenever these bubbles suddenly burst. These gas bubbles are harmless, though, and do not require medical treatment.

Excess tissue

Sometimes, if a serious knee injury is not treated or fails to heal properly, excess unnecessary tissue, called plica, can develop. This extra tissue can cause clicking sounds when you extend your knee. Medical intervention usually is not necessary, but if it becomes painful or interferes with your daily life, it’s best to speak with your doctor.

Meniscus tears

Two thick, tough, rubbery, wedge-shaped pads of cartilage called menisci cushion each knee joint. Three bones form this hinge-type joint — the femur (thighbone), the tibia (shinbone), and the patella (kneecap) — and the menisci act as shock absorbers between the femur and tibia. Meniscus tears are a common knee injury, particularly among athletes. However, you don’t have to be a professional basketball, football, or tennis player to experience such a tear. Sudden, forceful twisting of the knee, especially when putting your full weight on it, can cause a meniscus tear. Sudden stops and turns or heavy lifting also can result in a meniscus injury. The risk of a meniscus tear increases with age as, over time, meniscal cartilage deteriorates and weakens. A popping sound may occur when you tear a meniscus. Pain, stiffness, and swelling also may follow along with difficulty straightening your leg. If the tear is small and is on the outer edge of the meniscus, and your knee remains stable and pain-free, you may not require surgical intervention. Rest, Ice, Compression, and Elevation — known as the RICE protocol is often effective. However, if the pain or swelling persists or if you have trouble moving your knee, it’s best to consult your doctor. Surgical repair may be necessary. Left untreated, some meniscus tears can lead to decreased range of knee motion, persistent pain, and an increased risk of developing osteoarthritis.


The aging process is accompanied by changes in your body’s cartilage — it becomes thinner, making it more difficult for joints to work their best. And osteoarthritis, or degenerative arthritis, is the most common form of arthritis to affects the knee joint. The slick knee cartilage becomes rougher with age and may even wear down completely, resulting in bone rubbing on bone. Pain results. You may hear a grating or creaking sound as you move your knee. Maintaining a proper weight and staying active can slow the progression of osteoarthritis. Over-the-counter analgesics, such as acetaminophen (Tylenol) and non-steroidal anti-inflammatories (NSAIDs), can help to combat pain. Hot or cold compresses, knee taping, knee braces, and shoe inserts often provide relief for some people. Physical and occupational therapy, acupuncture, and stretching regimens such as yoga and tai chi also can help. However, more serious interventions may be necessary in order to alleviate severe or debilitating pain. These may include cortisone or lubrication injections, knee alignment surgery, or knee joint replacement.


Sometimes called "runner’s knee" or "jumper’s knee", PFPS is another of the most common causes of knee pain and knee clicking. Sports that involve large amounts of running and jumping can place repetitive stress on the patella, causing significant irritation. Sudden changes in physical activity, such as increasing the number of days you exercise or increasing the distance you run or jog, can cause PFPS as can changes in playing surfaces, footwear, equipment, or training techniques. Fractured or dislocated kneecaps can result in PFPS as well. In addition, muscle weakness or imbalances around the knee or hip fail to keep the knee properly aligned, causing PFPS. And, unfortunately, some knee surgeries, while solving the original problem — like a torn ACL — can result in some degree of PFPS. Popping or crackling sounds when ascending or descending stairs or changing from a sitting to a standing position are commonly associated with this syndrome. The RICE protocol can provide relief for many people. Changing or stopping your exercise schedule or regimen until the pain and sounds stop will give your knee an opportunity to heal. Maintaining a proper weight also helps. NSAIDs can reduce pain and swelling in most people. However, if the pain persists or it becomes increasingly difficult to move your knee, it’s time to consult your doctor. Physical therapy is often helpful and so are orthotics. Surgery, though, may be necessary for severe cases.

Snapping tendons or ligaments

Tendons and ligaments are types of soft tissue that keep the knee joint together. Tendons connect muscle to bone while the more elastic ligaments connect bone to bone. Moving the knee joint changes the position of the tendons as well as tightens the ligaments. A snapping or cracking sound can occur as these tissues move back into place. Although this noise may be bothersome, it’s not a cause for alarm and medical treatment is not necessary.

ACL injury

The knee joint is held together and stabilized by two types of ligaments. The cruciate ligaments — anterior (front) and posterior (back) — are deep within the knee and cross to form an "X". Each of these ligaments connect the femur with the tibia. A tear or sprain in the ACL is one of the most common knee injuries. It’s a very common sports injury, especially in those that include sudden stops, direction changes, and jumping. Athletes or even "weekend warriors" who play football, basketball, soccer, gymnastics, tennis, volleyball, or downhill skiing are at an increased risk of damaging their ACL. But this type of injury is not just confined to sports; it can result from a car accident or even work activities. A loud popping sound occurs with an ACL injury. Pain, swelling, loss of full range of motion, inability to bear weight, and a sensation of knee instability also occur. Although the RICE protocol can be used to immediately treat the injury, it’s important to promptly see your doctor so that a proper diagnosis can be made. Surgery is necessary in most cases. Physical therapy, a knee brace, and crutches are usually the next course of action.

MCL injury

There are two ligaments on either side of your knee, called collateral ligaments. The medial collateral ligament stabilizes the inner knee while the lateral collateral ligament stabilizes the outer knee. Both of these ligaments connect the femur to the tibia. MCL injuries most commonly occur in sports activities, such as football, soccer, and downhill skiing, where an action forces the tibia to bend overly outward in relation to the femur. When the MCL is injured, an audible pop occurs. Soon, pain, swelling, tenderness, and black and blue marks may occur at the inner part of the knee. Immediate use of the RICE protocol will help, but it’s necessary to consult your doctor for a proper diagnosis and subsequent treatment. Surgery is almost always necessary. Rest, a knee brace, and physical therapy may significantly help after surgery.

Chondromalacia patella

Chondromalacia patella occurs when the cartilage underneath the patella softens and breaks down, making the patella and femur rub together. Misalignment of overuse of the patella is usually the cause of the deteriorating cartilage, although excess weight is also a factor. Chondromalacia patella can occur when PFPS is left untreated. Pain is usually felt underneath and/or at the sides of the patella, and swelling often occurs as well. You may hear clicking or popping when you bend your knee. Or, you may hear crunching when you climb stairs or squat. Simply kneeling can be extremely painful. The RICE protocol can help reduce the symptoms of chondromalacia patella as well as over-the-counter medications such as NSAIDs and acetaminophen. Knee bracing alone or combined with taping can provide relief for many people. If the pain persists, it’s best to see your doctor. Physical therapy may be in order. In severe instances, surgery may be the best option.

Rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disease, which means your body’s immune system mistakenly launches an attack on your own body. It differs from the wear-and-tear damage of osteoarthritis as it attacks the lining of your joints, known as the synovium. The resulting painful swelling can result in deformed joints, destroyed cartilage, and bone loss. Knee sounds can occur as you try to move your affected knee. You also may experience fever, weight loss, and fatigue. Because rheumatoid arthritis is a chronic inflammatory disease, it can affect other parts of your body, including blood vessels, eyes, lungs, skin, and heart. Symptoms may not be constant and may come and go, with periods of flare-ups alternating with periods of remission. Consulting with your doctor is the best means of managing rheumatoid arthritis. NSAIDS may help, although prescription medications such as steroids, disease-modifying antirheumatic drugs (DMARDs), or biologic agents may be necessary. Physical and occupational therapy may provide some relief. Sometimes, however, surgery to repair the damaged synovium or tendons or knee replacement surgery may be the best treatment option.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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