For patients suffering from rheumatoid arthritis (RA), structural damage, i.e. bone erosion and joint space narrowing, is a major factor leading to functional disability. Negative radiographic progression has been shown in joints, especially in RA patients treated with tumor necrosis factor alpha (TNFα) inhibitors in combination with methotrexate. Bone erosion repair in small joints have been observed but only one study selected large weight-bearing joints. We reported 2 cases of patients with severe seropositive juvenile RA who shown improvement of joint space narrowing and subchondral erosion in hip joint when treated with etanercept in combination with methotrexate for at least 1year. Two Japanese cases were also published but with different TNF inhibitors. The mechanisms of bone erosion or joint space narrowing repair are unclear. One study investigated whether bone erosions in rheumatoid arthritis patients show evidence of repair in metacarpophalangeal joints when treated with TNF inhibitors and MTX. These results suggested that repair in RA emerged from the bone marrow and the endosteal lining rather than the periosteal compartment. No study investigated joint space narrowing repair in hip joint in rheumatoid arthritis patients. Larger studies needed to confirm joint space narrowing improvement in hip joint in patients treated with TNF inhibitors and to explain the mechanisms of repair.