The majority of square shoulder deformities develop in young adults, and most patients have active tuberculosis at the same time. It is slightly more common in men than in women. The left side is slightly more common than the right side. The causes of square shoulder deformity are mostly related to bone deformity, bone tuberculosis and pulmonary tuberculosis. Bone deformity: Bone deformity is an abnormality or defect in the volume, shape, location or structure of an organ or tissue that becomes a square shoulder deformity. The early symptoms of square shoulder deformity are not easily detected and treatment is delayed. It is more common in young children. Bone tuberculosis: Most of the bone tuberculosis is secondary to pulmonary tuberculosis, but there are patients without a history of tuberculosis who have an insidious infection with the tubercle bacillus. Most of the TB nuclei occur first in the lungs, and after infection in the lungs the infection can travel through the bloodstream to many systems throughout the body, and square shoulder deformities can occur. Tuberculosis: Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis, which can affect many organs, with pulmonary involvement forming the most common. Patients with tuberculosis are an important source of infection for square shoulder deformity.