Thank you all for you replies, they clear up a lot of confusion on my part. The scars on my knee that is being replaced are from shell fragment wounds from an RPG while in Vietnam. Still have pieces of shrapnel in my left arm that are rated at 20%. I receive compensation from other disabilities (Agent Orange cancer residuals, PTSD, left arm, hearing, and tinnitus) that all add up to 70%. I have been rated TDIU permanent and total since 2003. The temporary 100% for the knee with the other that add to70% will let SMC-S kick in for 1 year.
I thought that the gentleman I spoke with in person at the Regional Office was wrong. He said that I was ineligible for SMC-S. Thanks to Hadit I know that he was wrong.