Gillian's ACL dilemma

Hi!
I had a knee arthroscopy 13 years ago (when I was 15) to trim a torn cartilage. During this procedure it was noticed that I had also torn my ACL. A few months later I went back into hospital and had my ACL reconstructed (using a hamstring graft). Since that I returned to athletics and normal sporting activities (although I can't quite remember how long my recovery time was back then).
Recently I sat down and my knee 'clicked' It became badly swollen and locked so that I could not straighten it properly. 3 days ago I underwent another arthroscopy. The surgeon had to trim more cartilage and stated that there was substantial cartilage damage (both sides damaged as is the articular cartilage). He has also told me that my ACL reconstruction looks degenerated and weak and there is quite a bit of movement in my knee due to this. My dilemma is whether to have a second ACL reconstruction. I am 29 years old now and still very active (although I don't train or compete at a national standard now). Has anyone else had problems so long after an ACL reconstruction? Any comments would be appreciated.