My older DS (level 8) hyperextended both knees in practice about 6 or 8 weeks before first meet of the season. We never got a diagnoses of anything in particular, just a knee sprain, both knees but way worse on one side. It was so frustrating because when he was a level 6 he had patellar tendonitis for months and that muffed up that season too.
Anyway, this time, doctor said no gym or any other physical activity (aside normal every day) at all for 2 weeks, and then limited practice only, no impact, for at least another 2 weeks. He patiently explained to my son that these types of injuries can take a really, really long time to heal and feel better and it is not a good idea to try to rush it. And in fact DS, who was desperate to get back into the gym, found he really did need that long to heal. He was actually not able to start training tumbling or dismounts etc. for about 3 weeks after going back for limited training. But by the time he started training with impact again he and my husband and I really thought his body could handle it and were not worried the whole time something worse would happen. And so far, so good. He is competing now, but not all events.