Roughly 33 million Americans are living with osteoarthritis, a degenerative joint disease that can make it a challenge to get through the day. Here’s the latest on what causes the pain and stiffness and what may (or may not) help.

How arthritis starts 

The whole joint 

Researchers used to think that osteoarthritis was only due to wear-and-tear that, over time, broke down the articular cartilage—the cushioning that pads the ends of our bones.

“Now we recognize that all structures of the joint are affected,” says David Felson, a professor at the Boston University Chobanian & Avedisian School of Medicine.

That includes the cartilage, the bones, and the synovium—the lining of the joint that secretes fluid to keep it lubricated.

“You get inflammation in that tissue, called synovitis, and that leads to more inflammation, further damaging the cartilage and bone,” explains Felson.

Osteoarthritis can happen in most joints, but “the knees and hips are the most likely to cause people trouble,” says Felson. “The hands are often affected, too.”

Mechanics & inflammation 

Two long-term stresses can spur arthritis.

“One is mechanical,” says Stephen Messier, director of the J.B. Snow Biomechanics Laboratory at Wake Forest University. “That is, either excessive loads or normal loads applied in the wrong direction.”

Translation: Excess body weight, injuries, or even malalignment in the joint—like having knock knees or bow legs—can cause mechanical stress that puts the joint at risk.

But inflammation is also to blame.

“Think of a wound on your skin,” says Felson. “You get an inflammatory response that helps trigger healing. But the joint isn’t as capable of healing.” Why not?

Cartilage lacks a blood supply that delivers oxygen, nutrients, and white blood cells to repair the injury.

Instead, the inflammation causes more damage and more inflammation, eventually “leading to destruction of the joint and a lot of pain,” says Felson.

Knee injuries 

It’s not just the obvious injuries that boost your risk of osteoarthritis.

“Sure, it could happen to a football player who tears his ACL or someone who tears their meniscus playing tennis,” says Felson.

“But it could also be an unrecognized minor injury, like if you stepped off the curb wrong and somehow damaged a structure in your knee even though it didn’t bother you. Those small injuries can cause a defect in your cartilage, your meniscus, or some other place in the joint that leads to further damage.”

A meniscus is cartilage that acts as a pad between your shin and thigh bones. Each knee has two.

“The meniscus is like a washer,” Felson explains. “It provides a spacer between the two bones and the layers of cartilage at the end of the bones. When the meniscus gets damaged—either it tears or deteriorates—you lose that spacer function.”

“That means the joint leans a little toward the area where the meniscus has been damaged, so the knee is a bit malaligned and unstable.”

“Our data suggests that people with a torn meniscus—even those who aren’t symptomatic enough to warrant surgery—have a very high risk of developing osteoarthritis.”

Would arthroscopic surgery for a torn meniscus prevent osteoarthritis?

“If the meniscus can be repaired, that tends to be better long term than if the surgeon has to remove part of the meniscus,” says Felson. “But the risk of osteoarthritis may still be increased, with or without surgery.”

What to do 

Shed pounds 

Other than age and injury, excess weight is a main driver of osteoarthritis, especially in the knee.

“Due to rising obesity rates, we’re now seeing osteoarthritis in much younger folks,” says Felson. “Like 30- and 35-year-olds who have no history of major injury to their knees, but they just have too much weight that their joints can’t easily bear.”

Losing weight helps, even if you’re already suffering from arthritis.

Wake Forest’s Stephen Messier and his team looked at data from a trial where participants with knee arthritis lost weight by eating a low-calorie diet either alone or with exercise.

After 18 months, pain scores were 20 percent lower in those who lost 10 to 20—versus those who lost 5 to 10—percent of their weight.

“The more you lose, the more you improve,” says Messier. That also means that it’s easier to walk, stand, squat down, or kneel.

“Our studies show that for every pound of weight loss, there is a four-pound reduction in knee compressive forces for each step during walking,” says Messier. Lose 20 pounds, and your knees feel roughly 80 pounds less force.

Of course, losing weight and keeping it off isn’t easy. But that may change with new drugs like semaglutide (Wegovy) and tirzepatide (Zepbound), which lead to an average 12 to 18 percent weight loss.

In September, Novo Nordisk—the maker of Wegovy—completed a trial looking at knee pain and function in people with knee osteoarthritis who were given semaglutide for 16 months. Stay tuned for results.

Just keep moving 

Steering clear of exercise for fear that it’s going to further damage your knees or make your pain worse?

Stephen Messier is here to convince you otherwise.

“When people in our studies first start exercising, they say, ‘This hurts,’ and I tell them, ‘You just have to work through that initial bit of pain.’ We have decades of data to show that, in the end, that pain will go down.”

How much? In one of Messier’s studies, pain scores dropped by roughly 30 percent in people who combined walking and strength training. (And when people combined exercise and weight loss, pain scores dropped  by 45 percent.)

But Messier wanted to know if high-intensity strength training curbs pain even more.

“The idea is that you improve the strength of the leg muscles, and they act as shock absorbers and reduce the load on the knee,” he explains.

So he randomly assigned 320 older adults with knee osteoarthritis to a control group that attended monthly meetings about healthy living or to high- or low-intensity strength training groups that lifted weights three times a week.

“The high-intensity group lifted a higher percentage—about 75 to 90 percent—of the maximum weight they could lift, but they did fewer repetitions,” says Messier. “The lower-intensity group lifted about 30 to 40 percent of their maximum, but did more repetitions. As both groups got stronger, we bumped up the weight.”

After 18 months, “the intervention groups were significantly stronger compared to the control group.” But the high-intensity lifters got no stronger and had no less pain than the low-intensity lifters. So, at least for knee pain, there was no benefit—or harm—in heavier lifting.

The surprise: Pain scores dropped by 30 percent in all three groups.

“It made us wonder what we did,” says Messier. “Well, what we did is we paid attention to the control group. We didn’t just call them a few times throughout the study. So we’re wondering how much of the reduction in pain with exercise is just due to paying attention to people.”

It’s too early to know if other studies will find similar results. In the meantime, Messier still prescribes exercise...and not just for its impact on knees.

“I’ve been running with the same group every Sunday for the past 30 years,” he says. “My wife has her spinning group. These are huge parts of our lives.”

Messier’s bottom line: “Exercise is a good thing for everybody, but certainly for people with knee osteoarthritis.”

The good news: No type of exercise—walking, strength training, yoga, tai chi, etc.—seems to help more than any other for arthritis.

“Exercise however you want, but do something,” Messier urges.

Can exercise and weight loss help prevent osteoarthritis in people at higher risk? Messier is conducting a study in women over age 50 with obesity to find out.

Supplement savvy 

In 2022, the global market for bone and joint health supplements was estimated to be worth $11.7 billion. But the evidence that most of them do much—if anything—is underwhelming. (Nor is there much evidence that any foods help curb osteoarthritis.)

Take glucosamine and chondroitin.

“Glucosamine and chondroitin are components of cartilage, so the idea was that you’d take these orally and somehow they’d get into the joint and into the cartilage,” recalls Felson.

And in early industry-funded trials, taking glucosamine and chondroitin markedly eased pain.

“But the well-designed, large, publicly funded trials have shown no effect on pain or function,” says Felson.

“So even though recommendations to take glucosamine and chondroitin have been removed from arthritis guidelines, they are still very popular and very lucrative supplements.”

Ditto for vitamin D and fish oil, both of which failed to ease knee pain in a large recent trial.

What about the supplements with the latest buzz: turmeric and curcumin (one of the active ingredients in turmeric)?

“There have been about a dozen trials, and they’ve all shown that curcumin works for knee arthritis,” says Felson. “But I’d characterize those trials as I’m-not-so-sure-we-should-trust-them studies.”

Many were company funded. “And some of them showed benefits that were roughly equal to getting a knee replacement. Come on; give me a break.”

For example, researchers randomly assigned 58 people with knee arthritis to take 500 milligrams of turmeric extract or a placebo twice a day. After six weeks, the turmeric takers reported a whopping 70 percent drop in pain versus just a 25 percent drop in the placebo takers. But the study wasn’t double blind: the researchers knew who was getting the turmeric.

“The initial glucosamine studies also showed huge effects that were ultimately disproved by better studies,” Felson points out. Curcumin may turn out to be helpful...but its promise may also vanish once larger, longer, well-done trials are conducted.

Help from the pharmacy 

Pain pills 

“We don’t have any treatments that slow the progression of the structural damage of osteoarthritis,” says Felson.

“What we have are non-steroidal anti-inflammatory drugs that help control the pain. The stuff you get over the counter—aspirin, ibuprofen, and naproxen—is pretty effective, though some prescription NSAIDs work better.”

The problem: All NSAIDs raise the risk of bleeding and cardiovascular disease, especially in older people.

“And osteoarthritis is a disease of mostly older people,” notes Felson.

Gels and creams 

“People who can’t—or don’t want to—take oral NSAIDs can take topical NSAIDs like Voltaren gel,” says Felson. “They’re widely used and very safe.”

But they don’t work for all joints.

“Topical NSAIDs are modestly effective for the superficial joints like the knees and hands,” Felson explains. 

But the hip joint is too far from the skin’s surface for the topical painkillers to do much good.

And topical NSAIDs may not work for hand arthritis, because people wash their hands a lot, effectively washing the gel down the drain.

Topical capsaicin (the compound that supplies the heat in hot peppers) may also offer modest relief for some.

“But if you get it in your mouth or eyes, it burns like crazy,” warns Felson. 

That’s why guidelines recommend capsaicin for knees but not hands. Just be sure to wash your hands well after you apply it.

Injections 

Not all injections into the joint work, says Felson.

Guidelines from the American College of Rheumatology recommend against using hyaluronic acid injections. In theory, they increase viscosity, working like WD-40 for the joints.

“The idea is that if you can increase viscosity, you can protect the joint structures,” Felson explains.

The problem: “When you inject hyaluronic acid into the joint, it only stays there for about 24 to 36 hours. It doesn’t seem to have any long-term benefits.”

In contrast, “corticosteroid injections offer dramatic reductions in pain. But they wear off in two or three months.”

Do they also cause the cartilage to deteriorate, as one trial suggested?

“We looked at data from the two biggest osteoarthritis cohort studies, where participants reported when they had corticosteroid or hyaluronic acid injections,” says Felson. “Hyaluronic acid is a good comparator for steroids because we know that it doesn’t work very well, but that it’s also not harmful.”

After eight years, “it made no difference whether people got corticosteroid or hyaluronic acid injections,” says Felson. “Their rates of joint deterioration and knee replacements were no different.” A French study reported similar findings.

“So it’s reasonably established that there’s no major harm of occasional corticosteroid injection on joint deterioration.”

By “occasional,” he means to treat short-term flare-ups.

“If someone gets a few injections to treat pain flare-ups, it won’t cause them trouble,” says Felson. “But are injections, say, every three months for years and years safe? We don’t know.”

Going under the knife 

Surgery

Considering arthroscopic surgery (which uses tiny instruments to see inside and repair the knee) for osteoarthritis? Not a good idea.

“Older people should be discouraged from arthroscopic surgery to clean their knee out or treat a meniscal tear,” says Felson. (Meniscal tears discovered later in life are common and often not the cause of knee pain.)

Researchers looked at 13 trials that randomly assigned nearly 1,700 people with degenerative knee problems like osteoarthritis to get arthroscopic surgery or a “conservative treatment” like physical therapy, sham surgery, or injections.

During the first three months, roughly 12 percent of those who had surgery reported less pain compared to those who got a conservative treatment. But by one year, there was no benefit in pain reduction, function, or quality of life for those who went under the knife.

“Arthroscopic surgery is a waste of time and money,” says Felson.

Joint replacement

Surgery to replace a hip or knee can eliminate the pain of osteoarthritis.

“Hip replacement is among the best surgeries of the 20th century,” says Felson. “The recovery is fast, and people are often thrilled with their results within a few weeks.”

Knee replacements, on the other hand, aren’t a slam dunk.

While most people report less pain, and they’re better able to walk, sit, stand, climb stairs, squat, take off their socks, and more, “about 20 percent are not happy that they got a knee replacement,” says Felson.

That’s because the recovery can take months or even up to a year. And some people end up with lingering pain or limited function.

“So I hesitate before sending my patients too early for knee replacement,” says Felson, “whereas I don’t hesitate at all for hip replacement.”

How do you know when you’re ready for surgery?

“It’s when you can’t put up with the pain anymore,” says Felson. “It’s when your knee or your hip is so bad that you just can’t do the things you want to do.”