Do your knees sometimes crackle and pop like a bowl of Rice Krispies? Naturally, you’re concerned when your knees squeak and groan and you might be convinced it’s a sign of knee problems, most notably, arthritis. But, that’s not necessarily the case. It’s not uncommon for knees without pathology to make a crackling noise when you bend down or squat. Although that noise might be disconcerting, it can be a sign of normal “wear and tear” and not necessarily a sign you need to seek medical evaluation. You may also be suffering from pain due to osteoarthritis.
The knee joint is the largest in your body and it’s a compound joint, being made up of two components, the patella femoral joint, where the kneecap connects with the femur, and the tibiofemoral joint, the point where the smaller tibia meets the kneecap. The entire joint is encased by a capsule called the joint capsule. Within the capsule is synovial fluid, a fluid that helps absorb friction.
Covering the bones within the knee joint is hyaline cartilage, a tissue that helps the knee move more fluidly and with less friction as it protects the bone. Another type of connective tissue called the menisci covers the ends of bones within the joint space. The menisci, of which there are medial and lateral, act as shock absorbers.
Along the outer surface of the bones are ligaments that help stabilize the knee. You’ve probably heard of people who have torn one of the ligaments in their knee. A complete tear of a ligament, particularly the anterior cruciate ligament in the knee, can be a career-ending injury for athletes. Tendons also connect the muscle to bone. As you’re probably aware, tendons can become injured or inflamed as well, especially with overuse.
So, now that you have a basic knowledge of knee anatomy, what causes those crackles and pops? The cartilage that covers the bones in your knee becomes thinner over time due to wear and tear. As the tissue becomes thinner and less smooth, the bones make more noise when they glide past one another, such as when you bend your knees. The ligaments that support your knees also become less flexible over time. As they become tighter, they may make noise when you bend down or squat.
If you only hear crackles and pops and don’t have pain or swelling in the knee, the noises are probably due to age-related changes in the connective tissue. However, pops and crackles require evaluation if you have pain or swelling in the knee. Crackling or popping sounds with swelling or pain can be a sign of a tear in the meniscus, usually due to trauma.
Since you have a medial and lateral meniscus, the discomfort is usually along the inside or lateral edge of the knee. Meniscal tears can happen suddenly due to trauma. If you make a quick turn or twist your body, it places stress on the menisci and can lead to a tear. In this case, you usually feel a sudden onset of pain and you might hear a popping sound.
However, meniscal tears can be subtle with a slow onset of pain and swelling in the knee, usually with movement. When a meniscus tears, a portion of the connective tissue can remain lodged in the joint. If that’s the case, you might find that the knee gives out or locks up when you move it certain ways. When you try to extend the leg, you may not be able to do it all the way.
Are Noisy Knees a Sign That You’re at Higher Risk of Developing Knee Pain?
We mentioned that cracking and popping usually isn’t a cause for concern unless you have knee pain or swelling. However, one study suggests that these noises may be a risk factor for future knee pain due to osteoarthritis. After following 3,600 participants, the researchers found that those who had popping, cracking, or grating sounds coming from their knees were more likely to develop knee pain over the next year than those with quiet knees. However, this was true only in people between the ages of 45 and 79. So, if you’re 30 years old with noisy knees, you’re probably aren’t at higher risk of osteoarthritis if your knees moan and groan.
Lowering Your Risk of Knee Arthritis and Pain Due To Osteoarthritis
Certain factors that predispose you to knee osteoarthritis, like genetics, you have no control over, but other factors you do. One of the most important factors for lowering your risk of arthritis of the knees is maintaining healthy body weight. The more you weigh, the more pressure and stress it places on your knees. Over time, this can cause the cartilage to break down. In fact, according to the Arthritis Foundation, every pound of weight you gain adds four additional pounds of stress to your knees and boosts the pressure on your hips by six-fold. Don’t let your weight gradually “sneak up” over the years.
Exercise, too, is an ally in the battle against knee pain due to osteoarthritis. Strength training helps strengthen the muscles, particularly the quadriceps, that protect and support the underlying knee joint. At the same time, they protect yourself against injury when you exercise. If you’ve had a ligament tear, fracture, or dislocation, you’re at greater risk of developing arthritis.
You may have heard that high-impact exercise predisposes to knee arthritis. Although you shouldn’t necessarily do high-impact exercise if you have severe osteoarthritis, high-impact exercise may offer some protection against developing it in the first place. In a Brigham University study, researchers analyzed inflammatory chemicals called cytokines in the synovial fluid (the fluid inside a joint) in young men and women after a run. What they found was the levels of key cytokines were lower after a run than before. We know that moderate amounts of aerobic exercise have an anti-inflammatory effect and this may be favorable for avoiding joint problems.
The Bottom Line
Cracking and popping when you squat or bend your knees isn’t necessarily an indicator that you have arthritis or some other knee problem – but if you have pain or swelling, you should get it checked out. If you are of a certain age, those cracking knees could indicate a higher risk of developing osteoarthritis.
WebMD. “What is Your Knee Telling You?”
Wiley. “Noisy Knees May Be an Early Sign of Knee Osteoarthritis”
Arthritis Foundation. “Osteoarthritis Prevention: What Can You Do?”
Brigham Young University. “Study: Running actually lowers inflammation in knee joints”