Quadrilateral foramen syndrome is relatively rare in clinical practice, often occurring behind the shoulder joint, and is a symptom of the axillary nerve crossing the quadrilateral foramen, including the compression of the axillary nerve by the local soft tissue vascular nerve bundle, or the damage to the axillary nerve from previous closed injection treatment. The treatment includes conservative treatment and surgical treatment. Conservative treatment mainly consists of nerve-nourishing drugs, including oral methylcobalamin and intramuscular adenosylcobalamin. If conservative treatment is not effective and the strength of the deltoid muscle is weakened, a quadrilateral foraminal decomposition of the posterior shoulder joint can be done. Generally, if the axillary nerve is decomposed sufficiently and the compression is released, the postoperative symptoms will be improved significantly and the strength of the deltoid muscle will be restored quickly.