New York, May 5 (IANS): People at high risk for knee osteoarthritis (OA) may be nervous and reluctant to participate in strenuous physical activities but a new study, which followed high-risk individuals for 10 years, showed that vigorous exercise did not increase their risk of developing OA and may even protect them from the condition.

Osteoarthritis is the most common joint disorder in the US, affecting an estimated 32.5 million adults, according to the Centers for Disease Control and Prevention (CDC). The knee is the most commonly affected joint.

The lifetime risk of developing symptomatic, radiographic knee OA (as diagnosed on an x-ray) is approximately 38 per cent to 45 per cent. The estimated median age of diagnosis is 55 years.

"Our findings convey a reassuring message that adults at high risk for knee OA may safely engage in long-term strenuous physical activity at a moderate level to improve their general health and well-being," said study researcher Alison Chang from Northwestern University in the US.

In this observational study of 1,194 persons at high risk for but without radiographic evidence of knee OA who were followed for up to 10 years, long-term participation in strenuous physical activities was not associated with risk of developing radiographic knee OA.

In fact, the vigorously exercising individuals in the study were 30 per cent less likely to develop OA, although the number was not considered statistically significant.

The activities included jogging, swimming, cycling, singles tennis, aerobic dance and skiing. Persistent extensive sitting was not associated with either elevated or reduced risk.

The researchers' analysis showed nearly 50 per cent of the adults at high risk for this disease did not engage in any strenuous physical activity over eight years.

"People suffering from knee injuries or who had arthroscopic surgical repair of ACL or meniscus are often warned that they are well on the path to developing knee OA," Chang said.

"They may be concerned that participating in vigorous activities or exercises could cause pain and further tissue damage. To mitigate this perceived risk, some have cut down or discontinued strenuous physical activities, although these activities are beneficial to physical and mental health," Chang added.

The study, published in the journal JAMA Network Open, revealed that adults at high risk for knee OA may safely engage in long-term strenuous physical activity at a moderate level.