Oh, stupid injuries. You love me so. I've had one that's quite similar, actually! Not long after I had taken up riding, I had to mount a mare without the help of my trusty mounting block. So, what do I do? Of course, find a chair. So, I move the horse right besides the chair, climb up, try mounting...and, as I had not been smart enough to place the chair where the terrain is even, I fell. With the chair. My foot in the stirrup. The chair fell on me and bruised one of my knees quite impressively. Of course, I didn't give up. I place the chair - again, in the exact same spot - climb it, try mounting the horse....fall down with the chair, the chair lands on my legs (don't ask - how, I think it had it's own evil plan) and cuts the other knee nice and deep. Meanwhile, the horse is standing still and looking down on me with a face that just yells out - you're stupid or what?!
I've still got a scar from that cut.