Knee osteomalacia with narrowing of the medial joint space may be caused by degenerative lesions of the knee joint or osteoarthritis. 1. Degenerative lesions of the knee joint: due to long-term weight-bearing of the knee joint or with age, the knee joint is used too much, and wear and tear occurs over a long period of time, resulting in the aging of the articular cartilage, and secondary to the formation of periarticular osteophytes and osteophyte hyperplasia, which will cause narrowing of the joint space of the knee joint. 2. Osteoarthritis: osteoarthritis of the knee can also cause narrowing of the knee joint gap, mainly due to long-term wear and tear of the cartilage in the joints, cartilage wear and tear can not be regenerated, the formation of osteophytes, resulting in a gradual narrowing of the joint gap, joint gap narrowing, and severe pain and discomfort and other symptoms. The narrowing of the joint space on the inner side of the knee joint due to osteophytes may also have other causes, so it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment under the guidance of the doctor.