Lumbar pain after ejaculation may be physiological, and may be related to pathological factors such as lumbar diseases, inflammatory diseases, kidney stones and so on. 1. Physiological factors: such as too large or too intense movements during sex caused by muscle spasms in the body, transient lumbar pain after ejaculation, the symptoms can be gradually relieved after rest. 2. Pathologic factors: (1) lumbar diseases: if you have lumbar disc herniation, lumbar muscle strain and other diseases, the lumbar and back muscles tighten during ejaculation, which may affect the muscles of the lumbar back, resulting in lumbar pain and other symptoms. (2) inflammatory diseases: such as seminal vesiculitis, chronic prostatitis is mostly associated with microbial infections, which can lead to local mucous membrane redness, swelling and erosion, and after ejaculation, pathogenic microorganisms can be accompanied by semen accumulation to the posterior urethra, which stimulates the local mucous membrane redness and swelling, and urethral pain, lumbago and other symptoms. (3) Kidney stones: Kidney stones can cause renal pelvis obstruction, and if the stone moves, it can also cause ureteral obstruction, which can cause post-ejaculatory back pain symptoms. Lumbar pain after ejaculation may also be caused by other factors, if the symptoms of lumbar pain after ejaculation can not be relieved for a long time or even aggravated, it is recommended to go to the regular hospital in a timely manner, and active treatment to avoid delaying the condition.