Pain when bending the knee should be treated according to its cause. Common causes include osteoarthritis of the knee, meniscus injury, chondromalacia patellae, etc. General treatment, medication, physical or surgical treatment, etc. are taken. 1. Osteoarthritis of the knee joint: When osteoarthritis of the knee joint strikes, it will cause pain when bending the knee. After that, you can follow the doctor’s advice to take drugs that nourish cartilage, such as glucosamine hydrochloride, and also need to brake, avoid strenuous activities, and take analgesic drugs, such as celecoxib, if necessary. 2. Meniscus injury: knee trauma, meniscus degenerative changes may cause meniscus injury, resulting in pain when bending the knee. For early injury, braking can be chosen, together with analgesic drugs, such as ibuprofen. If the symptoms are more serious, intra-articular injection of sodium vitrate can be performed, and if necessary, arthroscopic meniscectomy and other surgical treatments can be chosen. 3. Chondromalacia patella: Chondromalacia patella is caused by various factors that lead to wear and tear of the patellar cartilage, thus causing pain when bending the knee. Treatment can be prescribed to take medication that nourishes the cartilage, such as aminoglucose hydrochloride, and at the same time, squatting and up and down steps should be reduced. In addition to the above factors, rheumatoid arthritis, rheumatoid arthritis, gouty arthritis and patellar tendon injury may cause pain when bending the knee. Patients are advised to go to the hospital to improve the examination and active treatment after symptoms appear.