Knee Osteoarthritis Affecting Younger Age Groups

Data suggest that middle-aged adults will account for more than half of new cases of knee osteoarthritis, placing a greater burden on the health system.

Current trends indicate that nearly 6.5 million Americans aged 35 to 84 are expected to be diagnosed with knee osteoarthritis in the next 10 years, according to research presented at the American College of Rheumatology Annual Scientific Meeting in Chicago.

The study also found that individuals as young as 45 to 64 years will account for more than half of newly-diagnosed cases, which will increase the need for total knee replacements and place an additional burden on the US health care system.

“The large number of newly-diagnosed cases of knee osteoarthritis in younger individuals will lead to continued increases in the use of total knee replacement,” said Elena Losina, PhD, of Brigham and Women’s Hospital in Boston, the study’s lead author. “These data are consistent with the recently observed tripling of total knee replacement use in 45 to 65 year old persons in the U.S.”

Osteoarthritis (OA) is the most common joint disease affecting middle-age and older individuals. It is characterized by progressive damage to the joint cartilage and causes changes in the structures around the joint. These changes can include fluid accumulation, bone overgrowth, and loosening and weakness of muscles and tendons, all of which may limit movement and cause pain and swelling.

Researchers from the Brigham and Women’s Hospital used data from the CDC in a computer model called OAPol to estimate the number of newly-diagnosed knee OA cases in the United States during the 1990s and the 2010s.

Using the OAPol model, the team was able to simulate the onset and progression of knee OA in individuals with demographic characteristics similar to US-based population from age 25 until death. Data from the model were combined with CDC population estimates to project the incidence and course of knee OA in the United States during the time periods studied.

Dr. Losina and colleagues found that physician-diagnosed knee OA affects about 7% of Americans aged 45 and older. They estimate that Americans will be diagnosed with knee OA much earlier in life in the 2010s versus the 1990s. In fact, the average age of physician-diagnosed knee OA is projected to fall from age 72 in the 1990s to age 56 in the 2010s.

Additionally, they found that Americans aged 35 to 84 years are likely to account for nearly 6.5 million new cases of knee OA over the next decade, with those aged 45 to 64 years accounting for 59% of cases.

The results further revealed that Americans aged 45 to 54 at the beginning of the 1990s would account for an estimated 412,214 newly-diagnosed knee OA cases over the following 10 years. Among this same age group, the study found that in the 2010s, newly-diagnosed knee OA cases over the next 10 years are expected to exceed 2 million. That means about 5% percent of all Americans aged 45 to 54 would be diagnosed with knee OA over the next decade of their life, compared to just 1.5% in the 1990s.

“In the last decade, obesity and knee injuries have become more prevalent, possibly contributing to the increase in knee OA in younger adults,” said Dr. Losina in a statement. “These trends toward earlier knee OA diagnosis may have a dramatic economic impact on the U.S. health care system.”