Question about MMR.

I've been playing some ranked before the new season begins. And I currently am at Silver 3, with Silver 2 MMR( according to op.gg, my MMR is 1,366) However, before loading into my next match, I checked the MMR of my teammates and opponents. And noticed their mmr isn't even higher than Silver IV. Isn't MMR suppose to place you in games with people within your current ranking or MMR #? If possible could someone explain why this happened.