The phenomenon that the knee joint makes noise when doing flexion and extension activities is called knee joint snapping. Knee snapping is very common, and there are many reasons. Bone hyperplasia is only one of the reasons, but it is not the only reason. Possible causes of knee fracture are:

(l) Knee osteoarthritis: Knee osteoarthritis is more common in middle-aged and elderly people. It is characterized by pain, discomfort and swelling of the knee joint, and the knee joint bounces during exercise. X-ray film shows that there are different degrees of bone hyperplasia in bone joints.

(2) Meniscus injury of knee joint: Meniscus injury is more common in young people, with a history of trauma and strenuous exercise, joint pain, weakness, locking (the knee joint is stuck when it bends and stretches to a certain angle) and snapping. If the examiner fixes the thigh of the affected limb with one hand and rotates the calf with the other hand, and flexes and stretches the knee joint at the same time, there may be a click and pain. The meniscus injury is serious or the injury time is long, and the thigh muscle atrophy can be seen.

(3) Chondromalacia patellae: Chondromalacia patellae is more common in middle-aged and elderly people. There are swelling, pain and joint murmur during knee flexion and extension, and the symptoms are mild and severe, and all kinds of treatment effects are not ideal. During the examination, press the patella with the palm of your hand to make it close to the femoral condyle. When rotating the patella, the surface of the patella can be felt uneven, and there is a "rustling" sound when rubbing against the femoral condyle. At the same time, patients also have pain. Pain and discomfort can also occur when the articular surface of the inner and outer edges of the patella is squeezed by hand. X-ray showed that the patellar cartilage was uneven, local cartilage was damaged or incomplete, there were cystic changes under the cartilage, and hyperosteogeny could be seen at the edge of patella and femoral condyle.

(4) Cruciate ligament injury: Most patients with cruciate ligament injury have a history of external injury. After the injury, the knee joint continues to be painful and swollen, and the pain is aggravated when you can't walk or walk; When the knee joint flexes and stretches, the joint will make noise, and at the same time, there will be displacement between bones.

Note: Pathological joint snapping is very complicated. It is best to consult a professional doctor, find out the specific reasons and carry out corresponding treatment.