Cold knees may be caused by rheumatism, osteoarthritis or herniated lumbar discs compressing the nerves. 1. Rheumatism: When rheumatism causes joint involvement, cold knees may occur, which may be related to living in a cold and damp environment for a long time. 2. Osteoarthritis: Patients with osteoarthritis may experience synovial membrane hyperplasia, soft tissue inflammation, popping, pain, redness and swelling of the joints, which may also cause cold knees. 3. Herniated lumbar discs compressing the nerves: When a herniated lumbar disc compresses the sciatic nerve, cold knees may also occur. If you find cold knees, it is recommended to consult the rheumatology and immunology department or orthopedics department of regular hospitals in a timely manner, and follow the doctor’s instructions to standardize the diagnosis and treatment.