Hip arthritis is a disease caused by wear and tear on the cartilage of the hip joint or by the destruction of it due to certain disease factors. When cartilage is damaged for various reasons, its thickness thins or even disappears, which causes the joint surface between the femoral head and the acetabulum to become uneven. This results in pain, stiffness and instability of the joint. In some cases, the movement of the hip joint can be severely limited. How is arthritis caused? There are several common types with different causes, which are summarized below: 1. Osteoarthritis: It is one of the most common types of arthritis. The cause is degenerative changes in the joints, also known as aging of the joints. It is generally most common in patients over the age of 50, but can develop at any age if there is serious damage to the joint. Osteoarthritis most often occurs in the large, weight-bearing joints of the lower extremities, such as the hip and knee; it can also occur in the spine or upper extremity joints. Due to degenerative joint cartilage degeneration and narrowing of the joint space, patients often have osteophytes around the joints, which exacerbates the limitation of joint movement. 2, traumatic arthritis: from the serious injury to the bone and cartilage in the joint, can be accompanied by the rupture of ligaments and muscle tendons, such a joint is very unstable, very easy to produce wear and tear, accelerating the degeneration of the joint. 3, acetabular dysplasia: due to congenital or developmental reasons such as the acetabulum can not completely cover the femoral head, the weight-bearing area of the joint is therefore smaller, the pressure per unit area of the joint surface increases, so that the wear and tear of the cartilage accelerates and causes serious osteoarthritis. 4, infectious arthritis sequelae: the pathogens causing hip joint infection can be common bacteria such as Staphylococcus aureus, streptococcus, or special bacteria such as tuberculosis. The bacteria can be transferred from other parts of the body through the bloodstream or caused by a localized infection of the hip joint. Bacterial erosion and the body’s inflammatory response to infection can quickly destroy joint cartilage within a few days. An open injury to the hip joint can also lead to infectious arthritis. Most patients can successfully control the inflammation with medication, braking and physical therapy. However, when articular cartilage is destroyed, it can produce severe damage leading to a series of sequelae that are very difficult to treat. 5, ankylosing spondylitis: Most often seen in young male patients. This arthritis often has damage to the joint surfaces of multiple joints. The lumbar spine, cervical spine, hip and knee are the most common sites of lesions. Patients may experience severe pain in the affected joints, stiffness or even complete rigidity of the joints, and other symptoms such as anemia, wasting, and recurrent joint swelling. It is a systemic disease that involves not only the joints but also the ligaments, joint capsule and muscles around the joints. 6, rheumatoid arthritis: mostly seen in female patients, the onset of bilateral symmetry, often first in the small joints of both hands or feet, later can involve all joints of the body, mainly manifested as morning stiffness, joint pain, joint swelling and joint movement is limited, the lesion mainly involves the synovial membrane, and gradually erode the joint cartilage, so that the loss of joint function. 7, aseptic necrosis of the femoral head: after the fracture of the femoral neck, about 30% of patients with displaced fractures will have ischemic necrosis of the femoral head to varying degrees, especially displaced femoral neck fractures in the elderly. In addition to trauma, alcoholism and hormonal drugs are the main causes of ischemic necrosis of the femoral head in China. Due to the above mentioned reasons, the blood flow to the femoral head is interrupted, resulting in necrosis of the subchondral bone within the femoral head, which cannot withstand the pressure on the femoral head from weight or activity, followed by deformation of the femoral head, collapse of the joint surface, and gradual limitation of the joint function until it is lost.