For the leg knee produces soreness for the following reasons: 1, often appear is too much exercise, this situation will easily lead to changes in the pressure in the joint cavity, joint fluid increased. The joint cartilage rubs against each other severely leading to sterile inflammatory exudation, and also the synovial membrane is repeatedly squeezed, forming sterile inflammation, which can lead to knee pain. 2, prolonged squatting or standing can also lead to local muscle spasm strain, causing knee pain. 3, there is also the knee itself inflammatory diseases, such as septic or tuberculous knee arthritis, can also lead to knee pain. Some of them are caused by herniated lumbar discs, which can produce a variety of uncomfortable sensations in the innervation area, such as knee pain, pins and needles or chills, and need to be actively examined. There are also occupational diseases of the knee joint, such as tumors and meniscal cysts, which can also lead to a sore knee.