/u/420_PUNCH_YR_GRANDMA , what /u/akimbojimbo229 said here cant be stressed enough. When I was bowling LH (sliding on my right knee) I could tell the next day when my sole needed replaced. At the VERY cheapest, buy yourself a pair of Brunswick Stealth or Brunswick TPX-Us or BB.com HPXs. More expensive shoes are the SST-8s. They are worth the money, just giving you options. These shoes allow you to dial in your slide to give you more or less as you need it depending on the house and the humidity level. I use an S10 on the front and an H7 (red or blue leather) on the heal. My daughter uses a 3/4 S8 1/4 S6 on the front and the Graduated rubber heal.

My background, My son drug me kicking an screaming into a league in Sept of 2014. By this time I had had 3 acl replacement surgeries and 1 debriment in my right knee. As I got better, my right knee kept hurting more and more the day after. I broke down and bought the Brunswick Steaths (the cheapest shoe with interchangeable slide soles you can get) in March of 15'. When we started the league up in September again I could tell when my sole needed changed because my knee would start getting sore. I was using an S9 (1/2 8 and 10) or S10 depending on the humidity. Eventually I re-injured the knee while bowling in March of 16. The only good news about this was all I had to do was buy a new Slide sole and Traction sole and just switch them so I could bowl RH which I am still doing. I have raised my average RH almost over my LH average so this can be done. Oh, I'm going to be 43 this year so YOU CAN TEACH AN OLD DO NEW TRICKS.

As far as braces go, the one Jumbo mentioned will work great to relieve pain. I worry about all the pressure put on the joint, and if it starts moving around you could cause MORE damage to your cartilage. I would suggest something LIKE this for while you are bowling. It will help keep your knee in place left to right, and forward and backward.\

As Jimbo said above, if you have any questions please feel free to ask.

EDIT: One final thought, if you want to see how much pressure is being up on your knee at the line, google Sean Rash Sports Science. Very interesting video about the science of bowling, but when you come to a stop at the line, you are putting about 7x your body weight in pressure on your knee. Or in my case, a HIPPO...LOL