The most common causes of left arm tendon pain are generally the following two: first, local acute and chronic strain on the muscles and ligaments, resulting in local muscle, fasciitis, muscle strain, etc. In this case, the local muscles and ligaments will have more obvious pressure pain; second, the greatest possibility is that the upper limb nerve compression caused by cervical spondylosis, the upper arm has a more obvious radiating pain, this time the local upper arm There is no obvious pressure pain in the muscles and ligaments. The specific cause of the tendon pain in the upper arm should be checked by an orthopedic surgeon at the hospital and further examination should be conducted to clarify the diagnosis and further treatment.