The tendon pain behind the bend of the leg has the following possibilities: 1, popliteal cysts, cysts do not cause symptoms when small, without diagnosis and treatment of gradual increase, increase to a certain extent will involve the surrounding muscles, ligaments, nerves and other tissues, resulting in rest or walking leg bend pain. 2, acute strenuous exercise, easy to lead to the rear of the calf muscle strains, collision injuries, falls, sprains and other violent injuries can easily lead to the knee cruciate ligament injuries, medial collateral ligament injuries can cause pain and discomfort behind the bend of the calf. Ligament injury, can cause pain and discomfort behind the bend of the calf. 3, osteoarthritis of the knee joint, due to osteophytes, bone spurs, bone redundant, and the formation of free bodies, resulting in degeneration of the articular cartilage surface, joint space narrowing, walking knee friction is easy to produce pain and discomfort. 4, lumbar herniation of intervertebral discs, lumbar herniation of intervertebral discs compression of the nerves that innervate the muscles at the back of the calf, stimulation of the nerves, will lead to pain at the back of the leg bend, often combined with the lumbar soreness, and the back of the leg. Tendon pain, often combined with lumbar pain and discomfort, or only the back of the calf pain.