Knee Surgery

could be any number of things, unlikely to be ligaments in absence of a noticeable injury. Likewise cartilage.. but possible you could have some wear and tear to these if you played a lot of impact sports when younger. Also possible is early arthritis of the patellofemoral joint (kneecap/thigh bone joint). Steroid injections should be avoided unless you need temporary relief for a particular reason eg a race as they won't repair anything in particular. You may guess from my advice that I'm a doctor, but the bottom line is - see a specialist - best via your GP. Either a scan or arthroscopy will help diagnosis. Symptom relief with all the other services recommended above.
PM if you want any further advice.
Si

Sorry dude I was taking the piss. My knees fucked and in dire need off surgery :[