How secure are steri strips after a cut opens for a second time?

So about 2 weeks ago, I banged my knee up on a rock pretty bad (just below the kneecap) and had to get 15 stitches (10 external, 5 internal). Wednesday marked the two week mark after it happened and I got my stitches out. The cut had healed up pretty nicely and I had exercised prior to today but I was playing frisbee and slid in the grass, opening up the cut again. I went to my pediatrician (I'm 17) instead of the ER this time due to money and they decided to just put steri strips over it? I feel like they may not hold, and it seems like it could me more prone to infection.