Have you other symptoms ? (muscles pain, chills or fevvers, fatigue, cognition... symptoms of Pois)
Cases only with physical symptoms are rare but you can find some testimonies describing knees pain, back pain, shoulders pain , hip pain after ejaculation.
I think it's a sign of inflammation linked to hormonal fluctuation after orgasm.

thanx
well I'm a TBI patient from 3 years ago, and I get a some pain in the shoulders