LAS VEGAS – Young people who sustain an intra-articular knee injury while participating in youth sports are not only at increased risk for early posttraumatic osteoarthritis 3-10 years later as young adults, but they also are more prone to develop obesity and other modifiable risk factors for osteoarthritis, according to Jackie Whittaker, PhD.

“It appears that some of these young active individuals, after sustaining an injury which is itself a risk factor for osteoarthritis, are going down a pathway where they’re developing a second risk factor for the disease. This may accelerate the rate at which they get the disease and may very well also accelerate the rate at which the disease progresses after its onset,” Dr. Whittaker of the University of Alberta, Edmonton, said at the World Congress on Osteoarthritis.

She presented highlights from the Alberta Youth Prevention in Early OA study, an ongoing prospective longitudinal cohort study of the long-term consequences of sports-related knee injury. The study includes 100 individuals who experienced a sports-related intra-articular knee injury 3-10 years earlier, prior to age 18 years, and 100 controls matched for age, sex, and participation in the same sport but without a knee injury. Their median age at follow-up was 22 years. Their knee injury occurred at a median age of 16 years; 55% of subjects were female.

It’s well established from other studies that roughly 50% of youth who have a significant knee joint injury for which they seek medical attention go on to develop knee osteoarthritis within 10-15 years. The Alberta study focuses on the years between injury and OA onset in an effort to identify modifiable risk factors and develop interventions to delay or halt progression to the disease. There is a paucity of research regarding this crucial time period, Dr. Whittaker explained at the congress sponsored by the Osteoarthritis Research Society International.

“In Canada, we know that injury during sport and recreation is the No. 1 reason that youth between the ages of 11 and 18 seek medical attention, with an alarming one in three doing so. Knee injuries are among the most common of those injuries,” she said.

At follow-up, 29% of the group with a history of knee injury and 4% of controls already had OA as defined by MRI. The likelihood of MRI evidence of OA was 13.5-fold greater in patients who underwent knee surgery for their injury, compared with controls.

“We saw the highest risk, as expected, in patients with ACL [anterior cruciate ligament] and/or meniscal tears, but we also saw a twofold increased risk of OA in those with seemingly less severe injuries, like grade 1-3 medial and collateral ligament injuries,” said Dr. Whittaker.

“I don’t think we were really shocked that knee injury can lead to structural changes that can be associated with future symptomatic OA, but we were surprised to be seeing that as early as 3-10 years post injury. And we were also seeing greater adiposity, a higher rate of being overweight or obese, reduced physical activity, weaker knee muscular strength, and poorer performance on balance and physical function tests,” she continued.

Indeed, at follow-up the subjects with a history of a youth sports knee injury were 4.4-fold more likely to be in the top quartile of fat mass index, compared with uninjured controls, 5.7-fold more likely to be in the highest quartile for abdominal fat, 2.1 times more likely to be in the lowest quartile for total weekly physical activity, and 2.4-fold more likely to be overweight or obese by body mass index (BMI). They were significantly less aerobically fit as reflected in their performance on the 20-meter shuttle run. And they scored significantly worse on the validated Knee Injury and Osteoarthritis Outcome Score (KOOS), particularly on the knee-related quality of life, pain, and symptom subscales.

“The study is ongoing, but it has already contributed to identification of who we’re probably going to need to target for secondary prevention strategies: obviously, individuals who have torn their ACL and/or their meniscus, as was already well known, but perhaps also individuals that have had less severe injuries, those who have a high BMI or some other indicator of adiposity, and those at risk of becoming physically inactive,” Dr. Whittaker said.

She added that a key take-away message from the study, for which she is coprincipal investigator, is that reduced physical activity on the part of someone with a history of a youth sports knee injury is a big red flag. These patients need to address their modifiable risk factors for OA via physical therapy and rehabilitation, along with receiving education reinforcing the importance of lifelong musculoskeletal health.

“Reduced physical activity is a warning sign. Don’t wait for knee pain,” she emphasized.

The Alberta Youth Prevention in Early OA study is funded by the Canadian Institutes of Health Research and nonprofit organizations. Dr. Whittaker reported having no financial conflicts.

bjancin@frontlinemedcom.com

Knee injuries in youth sports bring double whammy