As the proud recipient of a variety of perineal injuries, I would be delighted to share my understanding of skid mark vs. tear.
I had 2 skid marks and a tear at my homebirth, and had a lengthy discussion w/ visual aids w/ my midwife as she explained the differences.
She used the knitted blanker on my bed as a visual aid--imagine for yourself something like a crocheted afgan, with nice open stiches and a little bit of stretch.
The afgan, not stretched, is your skin. When you pull on it, you'll see the threads and stiches begin to separate...that's a skid mark; the skin is compromized & under stress. If you pulled it even harder--ouch--it might not stretch out and be compromized, it might just give way, and that's a tear. No muscle is involved in either scenario.
With a skid mark, most of the tissue is stretching: the underlying muscle, fat 'n' tissue on top of that, and most of the layers of skin (but not the most superficial layer[s], hence, the injury.)
With a tear, the muscle stretches, but there's not enough oppertunity for the skin to also stretch, so it gives way.
My skid marks looked like a skinned knee, an abrasion. The thing that caused the abrasion was the pulling of tissues, versus the scraping of tissue on a hard surface like a skinned knee.
And of course, my friends, when the underlying muscle is
involved in the tear, it's a 2nd degree tear. Episiotomies are always 2nd degree injuries
, because they cut through skin and muscle by definition.
My experience with healing times:
skid marks = 24 hours
tear w/ no stitches at homebirth = 1-2 weeks
episiotomy = over a year
This is why I'm a cheerleader for natural injuries--if indeed an injury is going to happen, which it often won't with mom-directed pushing and any position other lithotomy with a doc between your legs! edited to add: yes, my skid marks were on the labia, way anterior, and the small tear was into the perineum. And holy smokes Darshani, you just got 3 mamas replying about skid marks within 2 minutes of each other!