It may begin as a slight twinge in your knee or hip when you get out of bed. Over time, that twinge may turn into persistent pain, swelling, or reduced range of motion—symptoms of a condition called osteoarthritis.

However, like many chronic conditions, doctors typically cannot diagnose osteoarthritis until it has significantly progressed and interfered with daily activities. Scientists are working hard to find ways to diagnose osteoarthritis earlier to prevent or slow the damage caused by the disease, which affects over 32.5 million adults in the United States and more than 500 million people worldwide.

Recent research indicates that osteoarthritis is not solely caused by everyday wear and tear on joints, much like the gradual deterioration of rubber treads on a tire. In some patients, persistent, low-grade inflammation may accelerate the disease’s progression or even cause it. Scientists now believe that damage can start long before symptoms appear.

A new study from Duke University, published last week, identified molecules in the blood of women that might serve as markers of the disease up to eight years before an X-ray detects changes in their bones.

“This tells us that there is an osteoarthritis continuum,” said Dr. Virginia Byers Kraus, lead author of the study and a professor of medicine at Duke. “You’re already on an escalator that’s leading you up the path to symptoms and X-ray changes way before we thought.”

What Happens in the Body with Osteoarthritis?

Osteoarthritis affects cartilage, the protective tissue that serves as padding between the bones in your joints, allowing them to glide over each other when you walk, climb stairs, or bend to pick up groceries. This cartilage constantly breaks down with exercise and daily activities.

“But our body typically knows how to repair itself,” said Dr. Elaine Husni, director of the Cleveland Clinic’s Arthritis and Musculoskeletal Center. The fluid surrounding joints contains enzymes that help remove worn cartilage, while special cells fix minor damage and rebuild cartilage.

In people with osteoarthritis, this cycle of breakdown and repair goes awry. In some patients, these enzymes may be too aggressive in removing cartilage, or the healing process may be much slower than the cartilage breakdown. In others, the body senses damage or stress in the joints, leading to inflammation. This inflammation triggers cartilage-removing enzymes, but if the body can’t reduce the inflammation after repairs, it can lead to further cartilage breakdown.

Carrying extra body weight is one of the biggest risk factors for developing osteoarthritis. Injuries from sports or repetitive motion also increase the risk, as do conditions involving increased inflammation throughout the body, such as diabetes.

Eventually, the cartilage loses its ability to cushion the bones, leading to pain, a crackling sensation when moving your joints, reduced range of motion, and swelling. Osteoarthritis symptoms are most common in weight-bearing joints like the knee, hip, and lower spine, though they may also occur in small joints in the fingers or feet.

How is Osteoarthritis Diagnosed?

When a patient presents with joint pain, a provider may check for swelling, test the joint’s range of motion, and order tests to rule out other problems or types of arthritis.

The current gold standard for diagnosing osteoarthritis is an X-ray, which can show changes in joint structure associated with the disease. The more worn the joint, the narrower the gap appears between bones.

However, by the time these changes show up on an X-ray, the joint damage is already significant. X-rays don’t always correlate with the severity of symptoms or pain. “You could have two patients with the same amount of joint space narrowing—something like two or three millimeters on an X-ray—but one patient could have a lot of pain and the other may not,” Dr. Husni explained.

While Dr. Kraus’s team and other researchers are studying biomarkers to make osteoarthritis easier to diagnose, it may take years to prove a blood test reliable enough for clinical use. Researchers are also investigating whether these molecular markers can be used alongside drugs in trials to measure the effectiveness of experimental treatments.

For now, patients rely on supportive treatments to manage pain, such as heating pads, physical therapy, and over-the-counter medications.

Knowing that osteoarthritis is a slowly progressing disease can help individuals take steps to reduce their risk or slow the wear and tear on their joints. Maintaining a healthy weight, staying active, and following a balanced diet rich in anti-inflammatory foods can support joint health and overall well-being.