There are two main reasons for a cold knee in summer: 1. In summer, the knee joint is exposed to the surrounding environment because the clothing worn is relatively small, which makes it easy to get cold. 2. Inflammatory lesions in the knee joint itself, such as degeneration of knee cartilage and osteophytes in the knee joint, can produce aseptic inflammatory lesions, and the inflammatory metabolites can stimulate the surrounding tissues. The blood supply to the knee joint will be reduced, and the altered blood supply to the knee joint will lead to lower than normal heat, resulting in a cold knee joint.