I'm going to clog a pool lane by walking to rehab my knee
Why are you going to the pool for your knee?
I want my knee to get better and walking in the pool is the best way.
If you need to do something like that to help your knee you should take your space and work on it. There must be enough lanes for others to swim.
Maybe I'll just go to the infirmary instead.
That sounds like a much better idea. They will be able to help rehab your knee, and you won't get in the way of other people trying to use the pool.