Itchy below the knee may be caused by skin diseases below the knee, or it may be caused by degeneration of the knee joint itself, or it may be caused by autoimmune diseases. 1. Skin diseases: Skin lesions below the knee may cause itchy symptoms below the knee, such as allergic dermatitis and contact dermatitis below the knee caused by allergic factors, as well as folliculitis below the knee caused by infectious factors. 2. Degeneration of the knee joint: osteoarthrosis of the knee joint may cause pathological changes such as the formation of bony cumbers in the joint and the proliferation of synovial membrane, etc. In order to fight against the degeneration of the knee joint, itchy symptoms below the knee may also appear in the process of repairing the knee joint. Osteochondritis dissecans of the tibial tuberosity may also cause symptoms of itching below the knee. 3. Autoimmune diseases:Patients with autoimmune diseases may also experience accumulation in the knee joint, causing itchy symptoms below the knee. Common diseases such as rheumatoid osteoarthritis, gouty arthritis and so on. Itchy below the knee may also have other causes, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.