# Why is my knee polka-dotted? **URL:** \ **Category:** Factual Questions\ **Created:** [August 31, 2009, 10:53pm UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422 "2009-08-31T22:53:29Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![twickster](https://avatars.discourse-cdn.com/v4/letter/t/ec9cab/32.png) [@twickster](https://boards.straightdope.com/u/twickster)\ **Post date:** [August 31, 2009, 10:53pm UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/1 "2009-08-31T22:53:29Z")
A month or so ago I pulled a massively klutzy move – fell, very hard, on one knee when I was walking up some hard-surfaced stairs. (No reason for the fall other than that I didn’t life my foot up high enough.) In addition to the swelling, bruise, and soreness, I had a couple of big ol’ scabs. They’ve healed fine – except the area where the scabs were is now polka dotted. [Picture](http://www2.snapfish.com/slideshow/AlbumID=1274035022/PictureID=36831016022/a=888834022_888834022/otsc=SHR/otsi=SPIClink/COBRAND_NAME=snapfish/), [picture.](http://www2.snapfish.com/slideshow/AlbumID=1274035022/PictureID=36848493022/a=888834022_888834022/otsc=SHR/otsi=SPIClink/COBRAND_NAME=snapfish/) I’m totally not asking for medical advice – I’ve healed just fine without professional attention – but does anyone know: What’s with the polka dots? My apologies for the picture quality – it turns out to be way harder than you’d think to take a decent picture of your own knee. ---
**Author:** ![Zulema](https://avatars.discourse-cdn.com/v4/letter/z/db5fbb/32.png) [@Zulema](https://boards.straightdope.com/u/Zulema)\ **Post date:** [September 1, 2009, 4:54am UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/2 "2009-09-01T04:54:52Z")
Was the stair surface textured in that pattern? ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [September 1, 2009, 4:57am UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/3 "2009-09-01T04:57:04Z")
Kneasles? ---
**Author:** ![brossa](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/brossa/32/3040_2.png) [@brossa](https://boards.straightdope.com/u/brossa)\ **Post date:** [September 1, 2009, 5:12am UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/4 "2009-09-01T05:12:48Z")
At first glance I’d suspect that the darker spots are surrounding the hair follicles on the knee. In a partial-thickness skin injury like bad road rash or a skin graft donor site, the epithelium grows back by spreading out from hair follicles, covering whatever raw surface is present. It’s tough to tell from the photo, but you may just be seeing the contrast between the new, untanned, highly vascular new epithelium (pink) and the older, tanned epithelium of the follicles that stayed intact despite the injury. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [September 1, 2009, 7:27am UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/5 "2009-09-01T07:27:07Z")
Stigmata. ---
**Author:** ![StaudtCJ](https://avatars.discourse-cdn.com/v4/letter/s/90ced4/32.png) [@StaudtCJ](https://boards.straightdope.com/u/StaudtCJ)\ **Post date:** [September 1, 2009, 7:48am UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/6 "2009-09-01T07:48:06Z")
Apparently a random deity decided you needed decoration. ---
**Author:** ![twickster](https://avatars.discourse-cdn.com/v4/letter/t/ec9cab/32.png) [@twickster](https://boards.straightdope.com/u/twickster)\ **Post date:** [September 1, 2009, 12:01pm UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/7 "2009-09-01T12:01:30Z")
> [@SP2263](#): > > Was the stair surface textured in that pattern? No. The area where I fell was low-pile carpet over something very hard (concrete or steel) – I was walking up some steps exiting an underground mall. > [@brossa](#): > > At first glance I’d suspect that the darker spots are surrounding the hair follicles on the knee. In a partial-thickness skin injury like bad road rash or a skin graft donor site, the epithelium grows back by spreading out from hair follicles, covering whatever raw surface is present. It’s tough to tell from the photo, but you may just be seeing the contrast between the new, untanned, highly vascular new epithelium (pink) and the older, tanned epithelium of the follicles that stayed intact despite the injury. Wow. Cool. That makes sense. **examines knee yet again** That would explain the slightly-imperfect regularity of the spots. Interesting – thanks! ---
**Author:** ![Magicicada](https://avatars.discourse-cdn.com/v4/letter/m/c67d28/32.png) [@Magicicada](https://boards.straightdope.com/u/Magicicada)\ **Post date:** [September 2, 2009, 1:06am UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/8 "2009-09-02T01:06:25Z")
I didn’t want to post until you heard from someone who knew what they were talking about (thanks, brossa), but I have had this happen, too, and more than once. I seem to remember that it was always on the knee or elbow, in other words, a bony rather than fleshy area. I’d vaguely thought it was some sort of pore issue. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [September 2, 2009, 1:18am UTC](https://boards.straightdope.com/t/why-is-my-knee-polka-dotted/508422/9 "2009-09-02T01:18:27Z")
You lost some of your skin in the injury. That’s just the skin growing back (regenerating). The areas between the bumps will fill in, quite quickly in fact. If you check every day you’ll see it smoothing out as it fills in. I am not a doctor, but I severely lust for Cameron. Peace, mangeorge