Certolizumab pegol was effective for treating residual synovitis after total knee arthroplasty in a patient with rheumatoid arthritis: therapeutic monitoring by ultrasound.

We present the case of a 59-year-old female who developed rheumatoid arthritis in 2007. Right total knee arthroplasty (TKA) was performed in 2008. Although she was treated with methotrexate (MTX) after the operation, this treatment was insufficient. Infliximab (IFX) was introduced in 2001, and she achieved clinical remission. Left TKA was performed in October 2014. Because active synovitis was not detected by ultrasound after the operation, IFX was discontinued. She had been treated with MTX 8 mg weekly. However, arthralgia of the bilateral knees developed in March 2015. Ultrasound showed synovial hypertrophy with vascular signals representing postoperative residual synovitis. She was given certolizumab pegol. According to ultrasound, the synovitis had improved after 3 months.