I suddenly woke up around 3 am with a major cramp in my calf muscle. Hurt like the dickens, and hurt even more when I tried to massage it out. I could feel a real knot in the muscle.
What would cause that? Still hurts a bit now, 12 hours later.
FWIW, I’ve had cramps that were probably attributable to dehydration.
I don’t have a an answer for you, but I’m chiming in to let you know you aren’t alone. I had the same issue about 6 months ago, woke up feeling like my lower leg was trying to twist itself off. 
Possibly stress.
I used to have them all the time, sometimes multiple times per night, at my stressiest worst back in the day.
Try the Leg Cramp pills with Quinine. I used to take them before going to bed and they significantly reduced the frequency - though they did not eliminate them.
Although…
*What does quinine do for leg cramps?
Q. It’s been suggested that drinking 2 to 3 ounces of tonic water before bedtime can prevent leg cramps at night. … Quinine is FDA-approved only for treating malaria and is sold with a warning against using it to treat leg cramps or muscle pain, because it increases the risk of bleeding and heart rhythm disturbances.*
Congratulations, you’re pregnant! Or dehydrated.
Standing and putting weight on the leg works best to reduce the pain. To prevent it drink a glass of water before going to bed, two if you drank any alcohol that day.
I had those in college when running track, most likely fatigue or dehydration(like Thudlow).
Ever since my accident, i have those most every night. I’m guessing it’s related to the nerve damage.
The way I get them out is to try to gradually stretch the calf, the cramp should break. Be very careful, you’re trying to stretch a muscle that’s under intense contraction.
You’ll likely have to stand up, good leg forward, cramping leg back and put your toes on the floor. Use your body weight to push back into the bad leg and force the heel down.
Exercising the day before (running, cycling, stair climbing, leg day), poor hydration, and potentially also vitamin deficiency (lack of calcium can do it to me).
Bananas (rich in potassium) are said to help.
^ This.
Plus (this will sound crazy, but…), you’re more likely to get Charlie Horses if you extend your foot while sleeping. If you keep your foot at a 90 degree angle to your leg, almost none–personal experience.
Yep, I used to get them all the time back in high school when I ran a lot, and I still get them occasionally when I over-stretch out my leg in the middle of the night. What works for me 100% of the time to relieve the calf cramp is to grab my foot and pull it up towards myself. That relieves it fairly quickly (like within about 2-3 seconds.)
Unfortunately, I did not discover this until my adult years. I suffered through probably around fifty or sixty cramps in my teenaged running days. My natural instinct was always to point my foot out and just massage my calf and wince in pain for the 10-15 seconds or so for the muscle to just naturally work itself out. I’m not entirely sure how I figured out that the opposite of my instinct is what works but, gosh darn it, it works every single time for me, and I must have had at least a couple of dozen in the last 20 years.
As per Chimeras’ point about stress, Northern Piper, were you fretting over the Ontario provincial elections result?
Any number of reasons. If there’s a night I don’t wake up with a leg cramp I’ll let you know.
A variation on this for me. As soon as I feel it starting, I pull my toes and foot up. If I act quickly, this usually stops it.
Yep! That’s exactly the maneuver that works for me.
The doctor I originally heard this from suggested I scootch down to the foot of the bed and hang my feet over the end (I’m mostly a stomach sleeper). It worked but my feet got COLD! Socks helped.
UpToDate has a lot to say on the topic. But the main message is that the cause of most such cramps is unknown but non life or health-threatening. Also, stretching exercises are the best way to prevent or minimize them.
Some of us have to be very careful about doing the 90 degree foot flexing thing–often if I try that, the cramp extends itself into those skinny muscles that run up the shinbone. Then the entire calf is involved and I can’t really flex my foot in either direction without making one of the cramps worse. If I’m really lucky sometimes it extends all the way up into my hip, locking up each muscle on the way in turn. This can be borderline dangerous, since I sleep in a pitched roof loft where the highest point is four feet tall and I have to get down a ladder to get the space I need to stand and walk it off–if the muscles are jumping and cramping in turn it gets very difficult to get down that ladder.
My triggers are dehydration (a biggie since I’m a terrible hydrator with almost no thirst signal) along with excessive tiredness, especially if I’ve been standing on concrete all day. I’ve learned to force myself to take on adequate fluids no matter how hard I’m working and especially before I go to bed. I’d rather have to get up and pee than to get woken up by that much pain.
You’re getting old.
Get used to it. It’s better than not.
For me, I have some stenosis in my back due to arthritis (according to my doctor) which may be causing it. Scared the hell out of me the first time it happened (and my wife, too, since I woke up screaming “it’s killing me! it’s killing me!”). For a while, I’d get up and walk around a bit and it would subside. Eventually, I found that by rolling over in the bed and getting my lower back to “pop” (like some people will pop their neck), it will go away quickly. This has worked well for the past several years. A few days ago, however, I had a similar issue develop in my “ham”, not the calf. Same solution, but I had to get up since I couldn’t get my back to “pop”. Once I got up and walked around for a minute, I could go back to sleep.
Most of the time those cramps are due to not having enough water in your system and they increase with age. I get them at least a few times a year. Easy to fix, however:
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As some have pointed out, if you wake up with it just starting to cramp and it hasn’t actually started to hurt yet, you can usually stop it from happening by stretching out your leg.
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If you wake up already in pain, get out of bed and walk it off. The walking motion I’ve found is even more effective than stretching the leg.
And (in addition to the good advice given already) - if there’s any chance it’s due to dehydration, get some water. I’ve cured leg cramps in myself just by drinking some water.