The possible diseases of knee pain when bending are knee degenerative disease, knee synovitis, calcium deficiency, etc. Commonly used treatments include medication, surgery, and so on. 1. Degenerative knee joint disease: Commonly used drugs include non-steroidal anti-inflammatory drugs such as acetaminophen, indomethacin, etc. Tramadol extended-release tablets, codeine, etc. can be used for patients who are not satisfied with the effect of the above drugs. When the above treatments are ineffective, glucocorticoids, sodium vitrate and other drugs can be injected into the joint cavity to relieve pain and improve the function of the knee joint. If necessary, surgical treatment can be used, such as arthroscopic cleanup, joint fusion, arthroplasty and so on. 2. Knee synovitis: massage, massage, acupuncture and other methods can be taken to relax the tendons, activate blood circulation and remove blood stasis, in order to loosen the adhesion of the tissues, thereby alleviating the condition. For those with more fluid in the knee joint cavity, puncture drainage can be taken and sodium hyaluronate can be injected into the cavity. At the same time, with the above medication. 3. Calcium deficiency: such patients should take calcium supplements, such as calcium gluconate. In addition to the above diseases, rheumatoid arthritis, trauma, hyperuricemia, etc. can cause the above symptoms, and appropriate treatment can be given according to the diseases. It is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment.