6 Knee Pain Causes That Have (Almost) Nothing to Do With Getting Old

Achy, creaky knees affect people of all ages. Find knee pain relief by pinpointing its cause.

Knee Pain in Runner
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Your knees are the largest joints in your body for a reason—you need them for practically everything you do. And as a result, they endure a whole lot of abuse. Knee pain is common among people of all ages, with about 18 million people seeing a doctor for it every year.

Knee pain can come with crunching, popping, swelling, or instability (or, if you’re extra unlucky, a combination of those). No matter your knee pain symptoms, though, you should call your doc if you can’t bear weight on your affected leg or have a visible deformity, since you may have a serious injury. You’ll also want to seek help if you have redness and swelling that’s accompanied by a fever, as this is a sign you’re battling an infection.

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The biggest risk factor for knee pain is lack of strength and flexibility in the muscles around the joint, which puts added stress on the knees, says Robert Kaufman PT, DPT, a clinical specialist at NYU Langone’s Rusk Rehabilitation. “When people are in pain, very commonly what will happen is the load on their body is exceeding their body’s ability to adapt to that load,” Kaufman explains. That “load” can come in many forms—those extra 15 pounds you’ve been carrying around, your new running routine—and in all of them, your muscles can’t give your knees the support they need to handle the extra stress.

Following a strength routine can help protect your knees—but you don’t want to focus only on your quads and hamstrings, says Miho Tanaka, MD, director of the women’s sports medicine program and assistant professor in the Department of Orthopaedic Surgery at The Johns Hopkins Hospital in Baltimore. Working on your hips and core muscles, too, will help to prevent any instability further up the body, so that your knees won’t have to work so hard to stabilize your body.

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Lots of things can make your knees ache, and often depend on your age and how much you exercise. Read on for the most common culprits.

Feels like: Pain below the knee or across the front of the kneecap

Might be: Tendinitis

Sad, but true: sometimes, an active lifestyle can backfire if you fail to safeguard your knees. Cyclists, runners, and people who participate in jumping sports (tennis, basketball) are prone to patellar tendinitis, which usually causes pain across or just below the front of the kneecap. This overuse injury causes inflammation in the patellar tendon, which connects the quad muscle to the shin bone. “If the body is not trained appropriately, the load you’re putting on it will be too much too soon, and you’re going to get these overuse injuries,” Kaufman says.

🚴‍♀️ Love spinning or cycling? Set up your bike properly: A saddle that's too high can cause pain in the back of the knee, while a saddle that's too low may cause pain in the front.

Feels like: Your knee is tender, swollen, and is warm to the touch

Might be: Bursitis

Bursae are small, fluid-filled sacs that surround the knee joint. They provide double-duty support, cushioning pressure points between the bones in the knees and lubricating the joint, which reduces friction when you move. When the bursae become inflamed, they swell up, increasing friction between nearby tissue, and causing pain, says Zachary Rethorn, board-certified orthopedic physical therapist and clinical faculty member at the University of Tennessee at Chattanooga. “Some of the major causes of knee bursitis include trauma through a fall or hit to the area; prolonged pressure on the area, like being on your knees for hours; overuse or repetitive strain, and infection,” he says.

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Feeling better after acute bursitis is a gradual process, and is most effective with the help of a physical therapist who can tailor an exercise program to your specific needs. However, when it first comes on, the best thing to do is rest (not totally, just a little more), limit activities that involve heavy use of the knees, and give the knee an ice massage for 10 to 15 minutes every few hours, Rethorn says.

Feels like: Knee pain when bending accompanied by popping, swelling, stiffness, and pain

Might be: Torn meniscus

One of the most common knee injuries, a torn meniscus involves one (or both) of the C-shaped cartilaginous cushions that are on either side of the knee. In young people, it’s most often caused by some sort of trauma or overly aggressive pivoting of the knee—such as in athletes playing basketball or tennis.

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As we get older, the causes of a torn meniscus tend to transition toward normal wear-and-tear degeneration. “Many people over the age of 30 have some wear-and-tear, or fraying, of the meniscus,” Tanaka says.

Although surgery is more common after a traumatic tear, people who feel their knees locking or catching might opt for surgery as well, Tanaka says.

🔪 Think twice before you go under the knife: recent research shows most meniscus repairs were unnecessary, and the patients would have had similar outcomes with physical therapy alone.

Feels like: A sudden pop in the knee, followed by pain, swelling, and an inability to bear weight

Might be: ACL tear

If you’ve ever heard an athlete tell you they tore their ACL (anterior cruciate ligament), it’s because athletes are the most likely people to injure this part of the knee. “The ACL is one of the key stabilizing ligaments in the knee,” Rethorn says. It keeps the knee from rotating too much and from bending forward. “ACL tears usually involve more than just the ACL. Over 50% of ACL ruptures are associated with meniscal tears as well.”

Any athlete who plays a contact sport, or one that involves pivoting, jumping, or planting the foot to quickly decelerate, may be at risk of injuring their ACL. But women are more at risk of injury than men, Tanaka says. ACL injuries typically range from a sprain (where the ligament isn’t torn) to a full-on tear, Rethorn says. And while physical therapy may help to remedy some of the pain, surgery is often the best solution.

“Walking and running without an ACL are possible, so some may choose not to have their ACL fixed. But often, the knee is not rotationally stable without an ACL, and therefore those who want to return to cutting and pivoting sports will undergo surgery to fix this,” she says.

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Feels like: Stiff, tender knees that crack and swell

Might be: Arthritis

Osteoarthritis is the wear-and-tear type of arthritis, and it often strikes the knees. The most common form of arthritis, it usually begins in your 30s, and is caused by the deterioration of the cushiony tissue in the knee. “Just like you get gray hair as you age, you start to wear down the cartilage, the meniscus, in the knees,” Tanaka says. Arthritis symptoms include stiffness, swelling, poor range of motion, and catching or grinding of the joint.

Other types of arthritis can also affect the knees, including rheumatoid arthritis and gout.

Feels like: Pain on outside the knee that extends up to the hip

Might be: IT band syndrome

Its name might sound daunting, but IT band syndrome is actually super treatable. The iliotibial band is a long band of tissue that runs down the side of the hip and attaches to the side of the knee. Runners, cyclists, and anyone else who repeatedly bends and straightens the knee are most likely going to overuse the muscles attached to the IT band. “The tightness can cause rubbing of the band over the side of the knee, causing inflammation and pain,” Tanaka says.

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But because the IT band is "firmly and uniformly anchored to the femur (hip bone) like a barnacle to a ship,” Rethorn says, it can be very difficult if not impossible to stretch. However, relative rest, like taking an extra day off of working out, and using a foam roller on the outside of the leg and knee can help.

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