Snap, crackle, and pop! It makes a catchy slogan for a breakfast cereal. But when you hear those noises in your knee, they are a cause for concern, especially when accompanied by pain.
Some people hear sounds like crackling tissue paper when they bend or straighten their knees.
Known as crepitus, the noise occurs when air bubbles are trapped in the synovial lining of the joint. It is usually harmless. But, when the crackling sounds combine with pain, the symptoms may point to a serious condition, like arthritis.
At other times, snapping sensations, cracking, and popping are symptoms of the conditions below.
Your ligaments are tough bands of tissue that connect bone to bone. Usually, ligaments glide over the knee joint. But if a ligament is torn or damaged, it can catch and create a clicking sensation. Four ligament bands work to support the knee and allow movement.
- The ACL or anterior cruciate ligament supports the front of the knee. A popping sound and knee instability are two signs of an ACL injury.
- The PCL or posterior cruciate ligament stabilizes the back of the knee. Backward hyper-extension of the knee or a twisting fall can injure the PCL.
- An MCL or medial collateral ligament connects the thigh to the lower leg bones on the inside surfaces of the knee.
- And finally, the LCL or lateral collateral ligament attaches the shin and thigh bones on the outer leg.
Stretched or torn ligaments surrounding the knee cause audible crackling, popping, or clicking. Along with the noises, people may feel grating sensations, pain, and instability.
Between the thigh and the shin bones are two shock absorbers, the menisci.
The medial meniscus cushions the inside of the knee. The lateral meniscus pads the outer part of the joint. Age and sports activities can increase the risk of meniscus tears. Snapping or clicking sounds resulting from meniscus tears often include pain.
Wear and tear on the knee joint can lead to a loss of cartilage and osteoarthritis. Cartilage protects the joints and allows the bones to glide past one another in a smooth motion. When cartilage thins because of arthritis, it may cause pain, swelling, and clicks during movement. The risks of osteoarthritis increase with age, weight gain, and repetitive exercise.
Runner’s knee or patellofemoral syndrome is another common cause of knee clicks.
This overuse injury causes the misalignment of the kneecap. As a groove wears in the cartilage, clicking is felt during movement. Runner’s knee is not just associated with running. Activities such as skiing, dancing, or biking also put pressure on the kneecap and exasperate the condition.
When should I see someone for a clicking knee?
If your knee clicks, snaps, or pops, stop any activity that causes the sensation. If the clicking worsens after two weeks of rest or if you have difficulty walking, make an appointment with an orthopedic provider.