Knee bending and pain can be caused by knee joint free body, meniscus injury, osteoarthritis, etc. Usually, medication and surgery are needed. 1. Knee joint free body: After the knee joint is traumatized, it can cause the collision of the knee joint surface, which can cause the articular cartilage to fall off, and when the bone fragments fall into the knee joint cavity, it can form free body, and when the knee is bending, the free body will be stuck in the pressure, which will cause the symptom of crunching sound and pain. It is necessary to seek medical treatment for arthroscopic knee joint free body removal surgery, and the effect of drugs and other treatments is not good. 2. Meniscus injury: meniscus injury caused by knee trauma, meniscus by the tibia and femur extrusion can be torn and rotated, when the knee is bent, can cause jamming and crunching and pain. The treatment is mainly through arthroscopic meniscus suture and partial resection molding surgery and other surgical treatments. 3. Osteoarthritis: knee osteoarthritis due to articular cartilage damage, can lead to knee bending, friction between the joint surfaces, crunching and pain symptoms. You can take anti-inflammatory and analgesic drugs such as Celecoxib orally as prescribed by the doctor, and lubricate the joint cavity by injecting sodium hyaluronate into the joint cavity, and when the condition develops seriously, you can have knee joint replacement surgery. When the knee bending creaking and pain manifestation, need to consult a doctor, under the guidance of specialists to actively carry out appropriate treatment, will help early relief of discomfort symptoms at the knee, do not blindly use drugs.