if the swelling went down and pain subsided you might be lucky enough to escape some major tendon damage. But like sturg said, tendons in knee joint is kinda flimsy and if you dont take care long standing damages can happen. Eg: U might have a small tear in one of the tendons, if you dont rest and let it heal it might completely tear apart causing life long probs on top of crappy cost to fix it. Now the question is does every one need an MRI? nope, if proper knee exam and clinical exam comes out okay u might be good with rest alone. If abnormal i would personally like more investigations done well i hope i scared you enough to take it easy , GAPS on the road, you can hit them any day in your future, GAP in knee will mess up every day in your future .