A complex interworking of ligaments, tendons and muscles support your knee joint. These must support your body weight during normal activities and added force when you exercise, particularly for high-impact activities like running. This means your knee is prone to injuries. If you experience a clicking or popping sound when you squat or bend the knee, this does not necessarily indicate a more serious condition. However, clicking can indicate you have an injury like a meniscal tear or arthritis.
Arthritis
Osteoarthritis is a condition that commonly occurs as you age. The knee joint is composed of three bones: your patella or kneecap, the end of your femur or thighbone and the top of your tibia or shinbone. These bones fit together and are supported by cartilage, ligaments, muscles and tendons. When the membranes and cartilage that support your knee begin to wear down, you may experience a clicking, crunching or grinding sound in the knee when you squat because parts of the knee bones are rubbing against each other. While you may not initially experience pain with osteoarthritis, you may find the clicking is accompanied by joint stiffness. This condition tends to develop slowly--if you suspect your knee clicking is due to arthritis, see your physician for recommendations on how to minimize the development of osteoarthritis.
Meniscal Tear
Your knee has two pads of cartilage known as a meniscus that protects and cushions the knee joint. Meniscal tears are a common athletic injury that occurs when your knee twists while you bear weight on it. This injury is characterized by a clicking or popping sound. However, when you experience a meniscal injury, you don't always experience pain or swelling. Mild meniscal tears may result in knee weakness or continual clicking that can go away as the meniscus repairs itself.
Diagnosis
While meniscal tears can repair on their own, it's important to see your physician to ensure the meniscal tear is mild enough to heal. Your doctor will listen to your knee and may recommend imaging scans to view the cartilage. A slightly torn meniscus increases your risk for future, more serious knee injuries such as a complete meniscal tear, which can make surgery necessary.
Additional Causes
Knee clicking is a common symptom and does not always indicate cause for concern. Sometimes an imbalance in the knee muscles can cause knee clicking. Stronger quadriceps can pull on your hamstrings, which can be especially increased when you are squatting. Knee clicking can be common after even a small amount of knee trauma, such as knocking or hitting your knee against a wall or object. If the clicking noise sounds more like a popping, there is rarely cause for concern.
