Same knee-another replacement?

I am a 55 year old man who had knee replacement surgery 7 years ago. Last month I thought my mower was going to tip over as I mowed the bank. As I put my leg out to catch my balance, my knee gave way and I went down. I have had alot of constant pain and swelling since then. I went to my family doctor and he sent me for xrays. The xrays showed that the area around the metal part of my knee is now loose. My doctor has also said that there is nothing that can be done to fix this except for replacing the knee again. I haven't been to the surgeon who did the surgery because it takes about two months to get in to him. I am an over the road trucker and can't arrange my schedule for alot of things. Any advice or suggestions? Is what my family doctor saying the truth?