There are very many reasons for pain in the back of the leg curvature of the knee, the most common are caused by the following conditions: a. The patient has recently walked too much or suffered local trauma, it will cause pain in the leg curvature. For such patients, most of them will recover slowly through strict rest and protection, local hot compresses, and topical application of blood-stasis ointment, such as blood-activating pain cream. Second, patients with osteoarthritis, posterior meniscal horn injury, or cruciate ligament injury can also cause painful symptoms at the back bend of the knee. For such patients, it is necessary to actively undergo MRI of the knee joint. Third, if the patient has popliteal cyst, it will also cause painful symptoms in the bend of the leg.