Have you ever heard a crackle in your knees as you stood up from a squat? Do your shoulders creak during lateral raises? Or maybe you’ve heard a “pop” deep inside your hip socket when you ease into Warrior II pose.
These cracking, creaking, popping sounds coming from your joints can be disconcerting, even embarrassing, but medical experts say most of them are harmless.
Normal movement causes some cracking and creaking in even the healthiest joints and cartilage. Some noises, though, are the result of cartilage damage from injury, loss of muscle tissue or conditions such as osteoarthritis.
Understanding what causes joint sounds is the first step in determining whether the racket in your body is just incidental noise or something that requires medical attention. In either case, learning how to better support your joints, especially as you age, may quell some of the clatter.
Totally Normal Noises
One of the most common sources of noise is gas — but not the intestinal kind. The joint capsule is filled with synovial fluid, which lubricates the joint and provides nourishment to the cells that form cartilage. The fluid contains dissolved gases, including carbon dioxide, nitrogen and oxygen. When the joint ligaments are stretched, either intentionally (knuckle cracking) or by accident (arching your back), the pressure within the capsule changes and it releases carbon dioxide in the form of bubbles. The cracking sound you hear comes from those gas bubbles bursting. When these bubbles burst, people experience a sense of spaciousness within the joint and a temporary increase in its range of motion.
Another common cracking or popping sound doesn’t come from within the joint at all. During movement, tendons and ligaments that cross the joint can temporarily shift position or drag across a bone. When they return to their normal position, they make a snapping noise. You may have heard this in your knees when you rose from a sitting position, or in your neck when you turned your head. It’s also common in the shoulders. Loss of muscle mass from aging hastens this effect because more bone is exposed. This sounds scarier than it is; it’s actually a normal and harmless occurrence.
Something called crepitus, on the other hand, is not so benign. It might manifest as a crunching sound when you bend or extend your knees and is often described as sounding like Rice Krispies popping in a cereal bowl. Crepitus occurs when there is damage to cartilage within the joint. Sometimes the damage is due to overuse or aging; sometimes it’s a byproduct of injury, such as a tear in the ligament or cartilage. It can also be an early sign of arthritis.
“Cartilage doesn’t have pain sensors, so we can injure it and not feel pain. Any ‘grinding’ or ‘clunky’ noises should be checked by a doctor,” says Raymond Brodeur, DC, PhD, adjunct faculty of osteopathic manipulative medicine at Michigan State University in East Lansing.
Listen to Your Body
Are all those “pops” and “clunks” signs of serious problems? That depends on how your joints feel. Pain, swelling, numbness and loss of stability are all signs that something is amiss. Noise without these symptoms is probably harmless.
Some experts even believe that when joints crack, the action stimulates the nervous system, leading to a relaxation response in the surrounding muscles. “When a cat arches its back, it’s actually stimulating the proprioceptors in its spine — that’s how it wakes up its body,” says American Chiropractic Association spokesperson Robert Hayden, DC, PhD. “Similarly, it feels good when you move a joint and restore the flow of information from the joint to the part of the brain that coordinates it.”
Moderate joint cracking also helps to keep your joints from stiffening up — and that’s a good thing, Hayden adds. “A rule of thumb when it comes to joints is that when motion is decreased, joints become less functional.”
But this doesn’t mean you should try to force a crack. Doing so repeatedly may cause long-term damage to your joint tissue and may risk destabilizing areas that support your body, such as the lower back. And in a delicate area like the neck, where there are arteries present, wrenching against the natural plane and range of motion could even lead to stroke, Hayden warns.
It’s fine if your joints crack on their own, but it’s best to leave most intentional cracking to a chiropractor or osteopath.
While you can’t silence all of the noise emanating from your joints, you can take action to protect and care for these workhorses. Eating a healthy diet, getting regular exercise, and minimizing factors that decrease bone health, such as smoking, can help keep your joints healthy, and potentially quieter as a result.
The dietary supplements glucosamine and chondroitin sulphate can help reduce pain and swelling in joints in some people, and may also help those with early or even advanced osteoarthritis, says Dan Matthews, MD, spokesperson for the American Osteopathic Society for Sports Medicine. “Cartilage and synovial fluid have these two elements in them, so you are supplementing that material in the body.”
And recent research indicates that eating foods that reduce inflammation in the body — those containing antioxidants and essential fatty acids — is good for your joints, too. Antioxidants such as vitamins E, C, A, B5 and B6 help maintain cartilage and support its repair. And essential fatty acids, particularly omega-3s like those found in nuts and cold-water fish, can help normalize joint function.
Regular exercise keeps joints mobile and, by building muscle, more stable. It can also help you maintain a healthy weight, thus reducing the burden on your joints. The American Academy of Orthopaedic Surgeons (AAOS) recommends at least 30 minutes of physical activity daily, even for people with osteoarthritis. (For folks with bone or joint damage, the AAOS recommends moderate non-weight-bearing activity, such as swimming.) Being active helps strengthen your bones and support healthy joints. Just don’t forget to build in time for rest and recovery.
“Cartilage needs the cycle of weight-bearing and relaxation to pump nutrients to the cells that maintain its structure,” Brodeur explains. “Too much weight-bearing exercise can damage the joint by tearing cartilage or forcing out synovial fluid, robbing cells of the nutrients they need to survive.”
Like most things in our bodies, aging affects the joints. Diminished muscle mass, changes in cartilage and age-related stiffness all affect how your joints move and the kinds of noises they make. Medical professionals say the best thing you can do for your body and your joints, no matter your age, is to improve your overall health.
“Stay mobile, stay active,” says Hayden. “Joints need to be moved and periodically stressed in order to stay healthy. Even if they crackle.”
To learn more about the relative risks of knuckle cracking, check out the Web Extra! below.
Kelle Walsh is a writer and editor in San Francisco.