Shooting pain in a muscle that quickly goes away

if anybody knows which way to turn your foot, let me know so I can make a note and put it by my bed You have to do the thing that seems like a Bad Idea: Stand on the foot. The spasm makes the foot point down/straight, so you have to make it go in the opposite direction. Also: Eat more bananas.

A charley horse (or a muscle spasm) is when the muscle involuntarily contracts and doesn't release. Hurts like hell, but I wouldn't describe it as "sharp" personally, and in the calf it's particularly obvious because if you poke it you can feel the muscle gone all rock-hard. Calf cramps are often blamed on electrolyte imbalance, and particularly potassium deficiency. I have often gotten them while lying in bed - occasionally when asleep. "Pulling a muscle" generally refers to a minor partial tear in the muscle. It's a trauma thing - not likely to happen when lying in bed, and not likely to repeat regularly. Simliar to a sprain (which is more or less the same thing involving a tendon or ligament.) A limb "falling asleep" is when you restrict the flow of blood and the limb goes numb. The actual sensation people are usually talking about is the prickling "pins and needles" feeling of regained sensation when the restriction is removed. (Not a doctor, just a battered old ex-jock far too familiar with this category of slang. All usages are modern Midwest USA.)

BTW, I wouldn't describe this pain as a "charley horse," based on wikipedia-ing that term. I wouldn't describe it as a cramp, either. For me, a cramp is a slightly diffuse pain often felt, say, in the gut when running while being dehydrated. This, however, feels distinctly mechanical in its origin, if that makes sense. Not chemical. To the extent that this question is as much linguistic as medical, I'll include the following -- I'm from the midwestern US.

For me, a cramp is a slightly diffuse pain often felt, say, in the gut when running while being dehydrated. They're actually the same thing, but intestinal cramps feel different because nerves in the viscera are arranged and behave a little differently (and the muscle is different, too.) Skeletal muscles are very mechanical and the cramps feel pretty mechanical to me - with a calf cramp, you can literally grab your foot and move it and feel where the "string" has been shortened.

Yeah, these. They're common. The trouble is that they're infrequent enough that you can't remember if pointing your toe up or down makes it better or worse. They hurt like hell. Come to think of it, if anybody knows which way to turn your foot, let me know so I can make a note and put it by my bed.

Excluding voodoo and ghosts, or vitamin deficiency and/or dehydration, the cause is likely to be soft tissue hypertension emanating from some variety of minor functional misalignment. (It's not unthinkable that your shoulder injury could be unrelated as losing use of an arm for a while could certainly have a subtle effect on gait.) Start foam rolling, or better yet, http://www.amazon.co.uk/The-Stick-TravelStick-Travel/dp/B000P7PVWU/ref=sr_1_1?ie=UTF8&qid=1352093626&sr=8-1 your calves and plantar fascia (some other great tools to get at these are a soft ball or wallpaper seam roller). Work on http://www.strengthcoach.com/public/1298.cfm. If none of this helps, a podiatrist, physio or even a good running store can give a gait assessment and advise on corrective footwear changes.

What you are saying (including your clarification) still sounds like a cramp to me. My occasional leg cramps feel quite mechanical in origin. The muscle itself goes all piercing and wonky.

Cramps are often intense and stabby, even in the belly area. For instance, have you ever gotten a "side stitch" while running or swimming? That's a cramp.

My vote is a muscle spasm.