Hello, Commonly masturbation does not cause knee pain. However, if you are not active or lack doing physical exercises, you are suggested to immediately start stretch & other exercises that will keep you agile & active. Knee pain can be caused by extreme contractions of the adductor muscles (& Gracilis) that connect your pubis to the knees. It will go once you get regular in your exercises. Other factors can be developing Gout, OA/RA. You are suggested to visit ER, get physically examined, get CBC, Urinalysis(R/E, C/S), tests for Gout, OA/RA done so that you can be treated if you are diagnosed with the pathology at the earliest. Ejaculating very little semen occurs when the semen enters the bladder instead of coming out of the penis. It happens due to stress, depression, anxiety or as a side effects of medications taken previously for mood disorders, depression, drug abuse, psychedelic drugs intake, etc. You are suggested to get physically examined & get investigations & tests done to rule out any prostrate problem, blocked sperm duct or obesity. If obese, reduce weight. It is reversible but it can become a permanent problem in case of severe nerve or muscle damage. No worries, there are surgery s that can correct it. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Nupur K, General & Family Physician