Here are 4 places on your body you should never foam roll, according to a pro

Massages are a great way to loosen up tense muscles, whether you're sore and stiff from sitting at your desk all day or doing an intense workout — but they can also be pretty expensive. If that kind of pampering isn't in your budget, take note: You can get similar benefits at home using a foam roller.

While foam rollers can help loosen tight muscles and relieve painful knots, they should be used carefully. Improper foam rolling can injure several parts of the body — for instance, your knees. In addition, you should always warm up before you begin so you're not digging into cold muscles (ouch!).

We asked Ben Fung, American Physical Therapy Association spokesperson and doctor of physical therapy, which areas to avoid when it comes to foam rolling (one area might surprise you). Below, you can also find out which types of foam rollers you should use on different parts of your body.

What is foam rolling?

Foam rolling is a way to give your muscles a massage using a cylindrical tool. Fung says foam rolling is typically done to create a "neurophysiological effect," which essentially helps the nervous system and the movement system (your muscles and tendons) work together. You can use foam rolling to cool down after a workout or even as a warm-up before your workout.

Here's how to do it: Place a foam roller under your body — avoiding any of the areas mentioned below! — and slowly roll your body back and forth. If you're rolling your back, you'll use your legs to help support yourself. If you're rolling your legs, use your arms to hold yourself up. Again, remember to do this after your muscles are warmed up.

Places you should never foam roll

Whether you're using a foam roller for the first time or you've been loosening your muscles with one for years, it's important to do it correctly to prevent injuries. One of the best ways to avoid getting hurt? Heed experts' caution when it comes to areas of your body you shouldn't be foam rolling.

Joints and bony areas

You should avoid rolling bony parts of your body including your kneecaps, elbows and ankles, Fung says. "The risk of excessive pressure on key bony prominences may cause injuries to the skin, and could result in minor joint sprains," he says.

You can, however, carefully roll the sides of your knees where there's more muscle. Just stay clear of your kneecaps.

Neck

The neck is a very delicate area, with eight cervical nerves. "Rolling on a joint or neck can yield too much pressure on those areas and is best done under the supervision and guidance of a physical therapist," Fung explains.

If you're experiencing neck pain, consult with a medical professional about other ways to soothe the discomfort — for instance, using tennis balls to gently massage your neck.

Lower back

This one may be surprising because the lower back is a sore point for many people. You want to be careful if you use the roller on your lower back, below the rib cage area. That's because this part of your spine is extra sensitive to pressure, Fung says, and your kidneys and liver are also located there.

Instead, you can try yoga poses to stretch out your lower back muscles — for instance, child's pose can help offer some relief. To get into this pose, place your hands and knees on the ground so that you're in a tabletop position, then slowly shift your weight back so your bottom is touching your heels, and stretch your arms out forward.

Injured areas

Any injured areas, such as pulled muscles or broken bones, should never be foam rolled because doing so could worsen your condition, Fung cautions. If you've never used a foam roller before and are being treated for an injury, he recommends seeing a physical therapist, who can show you how to properly use one.

Should foam rolling hurt?

"Muscle soreness is natural, especially when pressure is applied to a tender area," Fung says. However, you shouldn't be in pain using a foam roller. If you feel any pain at all while foam rolling, stop rolling immediately until a doctor can determine the cause.

If the pain you're experiencing is consistent whether or not you're using the foam roller, let your physician or physical therapist know. They can advise you on how to safely add foam rolling to your stretching routine to meet your goals.

What type of foam roller should I use?

You've got many options when it comes to foam rollers, as they come in multiple shapes, sizes, densities, textures and colors.

Texture: Smooth foam rollers are best if you're just starting out or have a low pain tolerance. Foam rollers with grooves and bumps tend to dig in deeper and are great if you want more of a deep-tissue massage.

Density: Foam rollers have different density levels, ranging from soft to hard, and some are even hollow. If you're not used to putting pressure on or rolling out tight areas, Fung suggests starting with something gentle and not as dense.

If you're a foam-rolling veteran, a dense foam roller will work best on your thoracic spine (the middle section of your spine). But if you're rolling your IT bands or your quadriceps, it's still probably better to start with a softer foam roller, Fung says, especially if you have sensitive muscles or a low pain threshold.

Size: One large foam roller should do the trick, but if you really want to be precise about the muscle group you're tackling, you may want to check out the smaller options. Generally, foam rollers range anywhere from 36 inches (the standard large size) for a full body roll and go down to around 6-12 inches for massaging your triceps, for instance. Medium sizes are great for rolling your legs.

Shape: Most foam rollers are cylindrical. But there are also collapsible options that lay flat for portability. And you can also try out contoured rollers, which are designed to avoid your spine and shoulder blades when rolling — a better option if you're sensitive in those areas.

Now that you know which areas not to roll, you can get started on massaging those muscles. And if you still feel sore after foam rolling, try one of these 11 best pain-relieving creams for some additional relief.