If you have osteoarthritis (OA), you know it’s no fun. The joint pain and stiffness can interfere with daily activities and enjoyment of life.

But keeping osteoarthritis in check may be a simple as drinking a glass of milk, according to a study investigating osteoarthritis of the knee — at least if you are a woman.

Osteoarthritis is a common condition of aging joints. A chronic disease that affects roughly 27 million Americans, OA is caused by the breakdown of cartilage, the cushion between the bones in joints.

As cartilage deteriorates with age, it causes bones to rub against each other, leading to inflammation, pain and stiffness and eventually making it difficult to use the affected joint.

Women who drank the most milk showed the greatest improvement in knee joint space width.

For some, the disease progresses quickly, but for most people joint damage develops slowly over time.

Over 2,000 men and women with OA of the knee (3,087 knees) participated in the Osteoarthritis Initiative at Brigham & Women’s Hospital in Boston. Researchers collected information about participants' diets and x-rayed the joint space in the knee at the beginning of the study, measuring its width.

After four years in the study the women who drank the most milk had the most beneficial effects. They showed the greatest improvement in knee joint space width. Even when researchers adjusted for other dietary factors, body mass index, and disease severity, the results remained the same. Interestingly, men in the study didn’t see the same benefit.

Not all kinds of dairy products seem to help. Eating cheese actually increased the progression of knee osteoarthritis in women. Yogurt made no difference one way or another in either men or women.

“Our findings indicate that women who frequently drink milk may reduce the progression of OA,” said Bing Lu, MD, DrPH, of Brigham & Women’s Hospital in a statement, though he acknowledged that further study is needed.

The exact cause of OA of the knee is not known, but aging, being overweight, and stress injuries are common causes. It mainly affects those who are middle-aged and older, and appears to be more prevalent and severe in women.

“With the aging population and increase in life expectancy, there is an urgent need for effective methods to manage OA,” write Shivani Sahni, PhD, and Robert McLean, DSc, MPH, in an editorial on the study.

Though much remains unknown about the association between dairy foods, or at least the nutrients in them, making sure more seniors consume milk or other dairy products could be a step in the right direction.

The study is published in Arthritis Care & Research.