When I was 15, I "tweaked" my knee skiing, and I went down on a sled. The ski clinic checked me out, decided it was a sprain, braced me, and I was sent home. Sometime in the next few days, I was walking diagonally up a hill (no snow - just a regular hill), and my knee went out. Eventually, an MRI and surgery showed that I had partially torn the ACL, sprained the MCL, and torn up some meniscus for extra points. It's unclear which incident caused what damage, but I suspect that the second fall was caused by being a 15-year-old wandering around with an undiagnosed partially torn ACL, sprained MCL, and torn meniscus, and the second fall didn't cause more damage.
Whether to go to the ortho now depends on how active the patient is, their age, and their level of pain and stability when doing whatever activities they do. Someone who is 70 and only walks on flat, paved sidewalks will have a different calculus than a 40-something who plays rec league basketball once a week.