Left shoulder blade seam pain may be related to muscle strain, myofasciitis, or periarthritis. 1. Muscle strain: prolonged sitting in a fixed position or excessive weight bearing on the shoulder will lead to muscle strain on the back of the shoulder, resulting in shoulder pain or stiffness and other uncomfortable symptoms, which can be manifested as pain in the left shoulder blade suture. 2. Myofasciitis: when the back of the shoulder is stimulated by trauma, cold and labor for a long period of time, it can cause myofasciitis of the back of the shoulder, which will cause pain in the shoulder joint and the scapular suture. 3. Periarthritis of shoulder joint: It is a disease in which chronic aseptic inflammation occurs in the muscles, tendons, synovial fluid sac and joint capsule and other tissues around the shoulder joint. Clinical manifestations of shoulder joint pain and activity limitation are the main symptoms, and localized pain in the scapular suture may appear in the early stage. There may be other reasons for the pain at one point of the left scapular suture, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or therapy.