I would get a Second Opinion before replacing anything.
In 1979 I broke my knee. (Fell off a motorcycle) An Orthopedic Surgeon Fixed it. He did a great job. Around 1995 I had some problems with that knee. My primary doctor prescribed NAPROXIN SODIUM for pain and referred me back to the original surgeon.
Over the next three days, I took the Naproxin Sodium and the swelling and inflammation I had had for a YEAR went away. The pain and swelling was GONE.
So I asked the Primary Doctor if he could give me a prescription with lesser strength for the remainder of his two week prescribed regimen. He said I could get a lesser strength "over the counter"....
ALEVE. = Naproxin Sodium. It's an Anti Inflamatory.
In the meantime, I went back to the original surgeon the next week and told him everything was looking good and I didn't see any reason to pursue further treatment. He Xrayed the knee and informed me that a NEW KNEE was required and I should schedule the surgery.
WHAT:..??? My knee problem had dissapeared. WHO knows better than ME how my knee feels.
I DECLINED his offer to replace my knee. Guess what...My knee has been fine ever since...15 years later....Surgery is a
Business. 
NB
PS: Naproxin Sodium ("Aleve") is an Anti Inflamatory. On the rare ocassions that the knee feels uncomfortable..I take a couple of ALEVES.