Shoulder is very hard, it may be caused by the following reasons: First, it is possible that the shoulder muscle strain or inflammation, the most common is the shoulder is often hard to lift things, long-term low head work life of people, resulting in local muscle strain, over time, there may be chronic inflammation and pain, muscle stiffness. Generally improve the usual work and life habits, do some massage, massage and put on some ointment, the symptoms will soon be slowly relieved. Secondly, there may be some degenerative changes in the cervical spine caused by cervical spondylosis, such as disc herniation, small joint misalignment or osteophytes, which compress the nerve root on one side and cause nerve pulling pain on one side, resulting in muscle soreness and pain in the upper limbs or back of the shoulder, leading to local muscle stiffness. To make a definite diagnosis, it is usually necessary to go to a hospital to have an X-ray, CT or MRI of the cervical spine to confirm the diagnosis. Thirdly, it may be caused by frozen shoulder. Inflammation around the shoulder joint causes shoulder dysfunction, resulting in a stiff feeling in the shoulder.