Tennis Elbow A guy walks into a doctor's office. When the doctor walks in, the guy says, ""Doc, I threw my arm out playing tennis. I just need a shot of cortisone."" ""No problem,"" says the doctor, ""but first, I need to take a urine sample."" ""Why on Earth for?"" ""Well,"" the doctor explains, ""We have a new urinalysis machine that can diagnose any known ailment just from your urine. So we just need a sample."" ""I don't have to go now,"" the guy says. ""Can I bring you a sample in the morni…