I found out recently that my ACL is torn. (the 2nd time). As my boat was on order and hadn't arrived, I wasn't willing to get the surgery and forgo my wakeboarding season. Dr. gave me a tricked out Don Joy and told me good luck. I've been out riding 6-8 times this year with no problems.
The Dr. did tell me I was at much greater risk of wearing down the cartilage in my knee over time w/o the surgery. This would result in some long term issues and maybe a replacement knee when I'm even too old to wakesurf.
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I plan on getting it fixed in Nov.