The causes of pain under the patient’s right bunion are as follows: First, bunion tenosynovitis: the bunion flexor tendon and tendon sheath are located underneath the big toe. If weight-bearing, activities, and sports are often performed, it is easy to cause the tendon sheath and tendon to rub against each other, and tendon sheath inflammation will occur, mainly manifested as pain in the sacral area of the bunion, and even a popping sound of the bunion will occur when the tendon sheath is enlarged. Second, bunion arthritis: Mostly due to age, degeneration and wear of joint cartilage, joint space narrowing, and peri-articular osteophytes can cause concentrated force in the joint, which can cause chronic pain in the joint when walking. Third, rheumatoid or rheumatoid arthritis: especially rheumatoid arthritis can cause pain in small joints throughout the body, and joint pain is often symmetrical.