anyone have or heard of the disorder where the cartilidge in your knees disenegrates?

I just recently found out I have that , and I dont know much about it. The Dr. Says I have to go to Physical Therapy, take this vitamin and they have shots of snythetic cartilage in my knees( forgot the name of the stuff) Starts with an 'S'.

he also said its rare to have it at 29 and in both knees like I do...

Anyone ever hear of this, or what the long term damage/senario is?

I'm slightly worried about it?

My dad has something similar. I dont know if its that the cartilage disintegrated or that many years of wear and tear just took too much of a toll on his legs (when he was younger, he was in lord knows how many accidents, thrown off a motorcyle, etc...) So i'm not sure if its directly related to disintergration or not, but either way, he basically has NO cartilage left in his legs. he goes for Silicone (i believe) gel injections... so it serves the purpose as Faux cartilage i guess.

before he started getting those shots, he was in complete agony... (i forget the names of the bones) But the bone from above the knee cap and the bone from below it were rubbing together. without the cartilage there, they were basically knocking into each other, and this can cause the bones to crack and suffer severe damage. almost like if you were to keep slamming 2 rocks into each other... eventually, theyre going to start chipping each other. the gel serves as a little cushion to pad in between that area (the job that the cartilage used to do). If you have more specific questions, just let me know, and i can ask him-- he's been going to the doctors for a LONG time for this (they also had him doing physical therapy, and when he mentioned his routines to another Dr, that Dr said that the exercises that he was given were actually detrimental to his problem, and that set him back even further, so Really, if you can get a 2nd opinion about PT exercises/routine, definately try to... just to be extra careful)