Sprained left knee boarding. I had my angles too wide (was trying out 30, -30) and the weight of the board on my knee during the lift rides got me. I could barely put weight on it, and walking up and down steps for about a month was a task. But like others said, take baby steps to strenghen the knee. i work out a lot, and couldn't put much weight on it for that month. After that I started with low weights and SLOWLY increased it up over months. This was last season, now my knee feels 100%. Actually, I feel a lot stronger than before because I consciuosly took the time to build up my entire lower body. Oh yeah, I changed back to my old angles too, lol.