Pain in the lower right side of the back may be related to the following reasons: 1. There may be muscle spasm here. For example, if the patient does some strenuous activities involving the upper limbs and trunk, such as playing basketball, it may cause spasm of the latissimus dorsi muscle or the erector spinae muscle below it, which may cause pain here. 2. Deep fasciitis of the back may exist. This type of disease is often due to the patient has been cold here, and then lead to aseptic inflammation of the deep fascia, resulting in pain. 3, may exist in the scapula related injuries. For example, if there is a fracture of the scapula here, then there may be pain. And both new and old scapular injuries may cause this kind of pain. 4, this symptom is likely to be caused by lesions inside the right side of the chest. For example, if the patient has fluid in the right side of the chest, pleural adhesions or serious pneumonia, etc., it may cause pain here.