Knee clicking, or crepitus, is a common sound or sensation from the knee joint. While it can be startling, it’s often harmless and doesn’t indicate a serious problem.
Normal Reasons for Knee Clicking
A common reason for painless knee clicking is joint cavitation, where gas bubbles form and burst within the synovial fluid. Synovial fluid lubricates the joint. When the knee moves, changes in joint pressure cause dissolved gases, like nitrogen, to form tiny bubbles. These bubbles rapidly collapse, producing a distinct popping or cracking sound, similar to cracking knuckles. This process is harmless and does not lead to joint damage or arthritis.
Another normal cause of knee sounds is the movement of tendons and ligaments over bony structures. As the knee bends and straightens, tendons or ligaments can momentarily snap or rub over protuberances on the bones, creating a clicking or snapping sound. For example, the iliotibial (IT) band, a thick band of tissue on the outside of the thigh, can sometimes snap over the lateral femoral epicondyle, a bony part of the thigh bone near the knee. This snapping is not painful and does not signify a significant issue.
Slight, painless wear and tear of cartilage can also contribute to some knee sounds as a natural part of aging. While minor cartilage changes can produce sounds, this is different from symptomatic arthritis where significant cartilage loss leads to pain and other symptoms. The joint surfaces may become slightly rougher, leading to a subtle grating or gritty noise as fluid flows over them.
When Knee Clicking Is a Concern
Knee clicking is a concern when accompanied by other symptoms, indicating an underlying medical condition. These symptoms include pain, swelling, stiffness, redness, warmth, or a feeling of instability. A knee that gets stuck or locks is also a significant indicator for concern.
Several conditions can cause symptomatic knee clicking. Osteoarthritis (OA), a degenerative joint disease, involves the gradual wearing away of cartilage that cushions the ends of bones. As cartilage deteriorates, bones can rub against each other, leading to grinding or grating sounds, along with pain and reduced mobility. Meniscus tears, injuries to the C-shaped cartilage pads, often cause clicking, popping, or a catching sensation, accompanied by pain and swelling.
Ligament injuries, such as tears to the anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL), can also result in a popping sound at the time of injury, followed by pain and knee instability. Patellofemoral pain syndrome (PFPS), also known as “runner’s knee,” involves pain around the kneecap, often due to misalignment or overuse, and can present with clicking or grinding sounds. Chondromalacia patellae, a softening of the cartilage under the kneecap, similarly causes pain and grinding or cracking sensations, especially with bending or extending the knee.
Addressing Knee Clicking
If knee clicking is associated with pain, swelling, limited movement, or impacts daily activities, seek medical advice. A doctor will perform a physical examination to assess the knee’s range of motion, strength, and stability. Imaging tests, such as X-rays or MRI scans, may be ordered to visualize the internal structures of the knee and help diagnose any underlying issues like fractures, cartilage damage, or ligament tears.
Non-surgical management is often the first treatment for symptomatic knee clicking. This includes the R.I.C.E. method: rest, ice, compression, and elevation. Physical therapy is often recommended, focusing on exercises to strengthen knee muscles, improve flexibility, and correct movement patterns. Weight management can also reduce stress on the knee joint. Over-the-counter pain relievers, such as nonsteroidal anti-inflammatory drugs (NSAIDs), may help alleviate pain and reduce inflammation.
For severe damage, like significant meniscus tears or advanced arthritis, surgery may be considered if non-surgical methods are insufficient. Arthroscopic surgery, a minimally invasive procedure, can be used to remove loose fragments of bone or cartilage, repair damaged cartilage, or reconstruct torn ligaments. Partial or total knee replacement surgery might be an option for extensive joint damage. The specific treatment approach is tailored to the individual’s diagnosis and the underlying cause of the knee clicking.