Waking up with a pain in your neck is, well, a pain in the neck. You know it probably came from you sleeping “funny,” but what exactly does that mean?

The answer starts with a quick anatomy lesson. Your spine is made up of three parts: the lumbar, thoracic, and cervical spines. The cervical part is at the top, and it’s essentially what you know as your neck.

Between the vertebrae of your cervical spine are joints, which give you the ability to turn your head and neck.When you sleep, the weight of your head can relax in an awkward position that irritates these joints, says Mike Reinold, P.T., C.S.C.S., a Boston-based physical therapist and performance enhancement specialist.

And if your joints are irritated, then there may be an inflammatory response and a protective muscle spasm trying to prevent the movement of that area, says Bill Hartman, P.T., C.S.C.S., Men’s Health’s sports medicine advisor. Hence the pain and stiffness.

The key to dodging morning neck pain, Hartman says, is keeping your neck as neutral as possible at night.

To do that, you’ll want to avoid sleep positions where your head bends excessively forward, backward, to the side, or turned in one direction, he says. If you’re a stomach sleeper, your neck turns to the side by default, so that might explain your A.M. pain.

Related: The Best Sleep Positions

The best solution is to sleep on your back, also known as the supine position. “The pillow supports your head and neck, but doesn’t push it forward,” says Hartman.

The caveat: If you have underlying health problems like sleep apnea or obesity, some research shows that sleeping on your back can lead to snoring. The position makes your airway less stable and more likely to collapse.

So if you can’t sleep on your back, turn to a side-lying position, but make sure you don’t bend your neck.

Not used to either position? Invest in a good memory foam pillow. The foam molds to your neck, keeping it aligned with the rest of your spine as if you were standing straight. Reinold recommends Tempur-Pedic pillows (tempurpedic.com).

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And if you do wake up sore, resist the urge to stretch—it’s counterproductive, and part of the reason why you’re in pain in the first place, Reinold says. Take a warm shower and gently rotate your neck to work out the kinks.