call your insurance company again and find out the exact wording of your PT allowance. Mine allows '20 sessions per calendar year per diagnosis" The diagnosis is really the code the PT files your sessions under with the insurance company. So, having talked to my insurance company many many times (because the PT receptionist couldn't understand), they would pay for 20 sessions per calendar year and that was it - for that code. So then talk to your PT and ask what code they've been writing you up on, and then ask that after those 20 sessions (if you need more), them to file under a different code - now it's a different 'diagnosis'. There is more than one PT code for knee problems. They can't use the TKR code - at least not with Aetna because that's reserved for OS, but there are still 2 or 3 other codes (including one called 'knee pain'!) they can use. That way they can stretch things out.
Because I had been to PT last January for about 8 sessions (and no longer see that PT - she was terrible) and then in Oct was starting up again after my TKRs, I asked the insurance company what code the first ones were listed as. I wrote down the numbers and gave them to my new PT and she just didn't use those and wrote me up differently. No problem!
but otherwise, unless you are going to pay out of pocket, when you reach your insurance limit they will stop the PT reagardless of whether you need more or not. Gotta love our health care system.