The common causes of soreness in the upper buttocks on the right side include gluteal myofasciitis, lumbar disc herniation, rheumatoid arthritis, etc. Accordingly, you can go to the hospital to see orthopedics, rheumatology and immunology (internal medicine). 1. Gluteal Fasciitis: Chronic aseptic inflammation of the fascia of the buttocks due to cold and fatigue can cause muscle pain on one side of the buttocks. 2. Herniated lumbar disc: Herniated lumbar disc compresses the nerve root of sciatic nerve, causing localized edema and inflammation, and along the direction of the sciatic nerve, resulting in soreness of the buttock muscles on the right side of the upper buttock. 3. Rheumatoid arthritis: it can lead to chronic inflammation of the sacroiliac joints and soreness of the right upper buttock muscles. Caused by the right side of the upper buttock muscle pain, there may also be other reasons, it is recommended to go to the hospital in a timely manner to the appropriate departments, improve the examination to clarify the cause of the disease, under the guidance of the doctor for standardized treatment.