Physical Activity in Childhood May Lead to Stronger Knee Structure as an Adult

Released: 11/7/2012 9:00 AM EST
Embargo expired: 11/10/2012 4:30 PM EST
Source Newsroom: American College of Rheumatology (ACR)
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Newswise — WASHINGTON – Being more physically active in childhood is linked to greater knee cartilage and tibial bone area in adulthood, according to new research findings presented this week at the American College of Rheumatology Annual Meeting in Washington, D.C.

Knee osteoarthritis is caused by cartilage breakdown in the knee joint. Factors that increase the risk of knee osteoarthritis include obesity, age, prior injury to the knee, extreme stress to the joints, and family history. In 2005, 27 million Americans suffered from osteoarthritis, and one in two people will have symptomatic knee arthritis by age 85.

While physical activity in childhood is often recommended as a means to improve adult joint health and function, little evidence exists to illustrate the correlation between childhood physical performance measures and bone structure in adulthood later on. The goal of the study was to determine if physical activity in youth was associated with more knee cartilage and tibial bone area (the bone that forms the distal part of the knee joint) 25 years later, says Graeme Jones, MD, PhD, investigator in the study and professor of rheumatology and epidemiology at Menzies Research Institute in Hobart, Tasmania.

Real-time data was gathered in 1985 on the childhood physical performance in a diverse group of 298 people in Australian. Of these, 48.7 percent were female and ages ranged from 31 to 41. The participant’s knee cartilage and tibial bone area were measured using T-1 weighted, fat-suppressed magnetic resonance imaging.

Although Dr. Jones and his colleagues had questionnaire responses on the physical activity level of the children taken in 1985, they found that current-day measurements revealed more accurate information.

Adjustments were made for age, gender, body mass index and past joint injuries that may affect the cartilage or bone area. The results showed that childhood physical activity, including physical work capacity, leg and hand muscle strength, sit-ups, and long and short runs had a significant, consistent association with greater tibial bone area. In addition, higher childhood physical work capacity measures were associated with greater tibial cartilage area. Other types of physical activity in childhood were associated with greater cartilage area, but these measures were less significant after adjusting for medial tibial bone area.

Dr. Jones and his colleagues do not know exactly why or how physical activity may build bone and cartilage years later. “The mechanism is uncertain, but I would contend that bone area gets larger to cope with the extra demands put on it by higher levels of physical activity, and then this lead to more cartilage, as cartilage covers the surface of bone,” he says.

While the study’s findings lend greater support to the effort in many developed countries to encourage children to be more physically active, cartilage and bone are still vulnerable to damage later on that could contribute to OA, says Dr. Jones.

“Physical activity is good, but if people have an injury while doing the physical activity, this is bad. So injury prevention is important. Avoiding a high body mass index is also important, and physical activity will help with this.”

This study was funded by NHMRC of Australia.

The American College of Rheumatology is an international professional medical society that represents more than 9,000 rheumatologists and rheumatology health professionals around the world. Its mission is to advance rheumatology. The ACR/ARHP Annual Meeting is the premier meeting in rheumatology. For more information about the meeting, visit www.acrannualmeeting.org or join the conversation on Twitter by using the official hashtag: #ACR2012.

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Editor’s Notes: Benny Samuel Eathakkattu Antony, MD will present this research during the ACR Annual Meeting at the Walter E. Washington Convention Center at 5:00 PM on Tuesday, November 13 in Room 152 A. Dr. Graeme Jones, PhD will be available for media questions and briefing at 1:30 PM on Tuesday, November 13 in the on-site press conference room, Room 203 A-B.

Presentation Number: 2535

Childhood Physical Fitness Predicts Adulthood Knee Cartilage Volume and Bone Area: A 25-Year Cohort Study

Benny Samuel Eathakkattu Antony (Menzies Research Institute, Tasmania, Hobart, Australia)
Graeme Jones (Menzies Research Institute, Tasmania, Hobart, Australia)
Alison Venn (Menzies Research Institute, Tasmania, Hobart, Australia)
Leigh Blizzard (Menzies Research Institute, Tasmania, Hobart, Australia)
Flavia Cicuttini (Monash University, Central and Eastern Clinical School, Melbourne, Australia)
Lyn March (University of Sydney, Institute of Bone and Joint Research, Sydney, Australia)
Terry Dwyer (Murdoch Children's Research Institute, Melbourne, Australia)
Changhai Ding (Menzies research institute & Monash University, Hobart, Australia)

Background/Purpose: Physical activity interventions are often advised for management of osteoarthritis patients, despite contradictory findings regarding its effect on knee structure. In particular, there is little evidence relating childhood physical performance measures to adult joint structure. The aim of this cohort study was to determine the associations between childhood physical performance measures and knee cartilage volume and tibial bone area in adults 25 years later.
Methods: Subjects broadly representative of the Australian population (n=298, aged 31-41 years, female 48.7%) were selected from the Childhood Determinants of Adult Health study. They underwent T1-weighted fat- supressed magnetic resonance imaging of their dominant knee and cartilage volume and tibial bone area were measured. Childhood measures including physical work capacity at 170 beats per minute (PWC170), leg and hand muscle strength, sit-ups, long-run, and short-run were measured by standard protocols 25 years prior.

Results: There were consistent and significant associations of all childhood measures including PWC170 (β: 0.48 cm2 per 100 mW, 95% CI: 0.22, 0.73), hand muscle strength (β: 1.49 cm2 per 100g, 95% CI: 0.79, 2.19), leg muscle strength (β: 0.29 cm2 per 100g, 95% CI: 0.09, 0.50), short-run (β: -0.71 cm2 per second, 95% CI: -1.21, -0.21) and sit-ups (β: 0.28 cm2 per count/10, 95% CI: 0.13, 0.43) with adult tibial bone area in multivariable linear regression, after adjustment for sex, childhood age, duration of follow-up and childhood and adulthood measures (body mass index and knee injury). In addition, these associations were independent of the corresponding adulthood fitness measures and tibial cartilage volume. Similarly, there was a significant positive association between childhood PWC170 and adult medial tibial cartilage volume (β: 0.1 mm3 per 100 mW, 95% CI: 0.03, 0.17) after adjustment for covariates including adult PWC170. The magnitude of the association decreased by 33% but remained significant after further adjustment for tibial bone area. Other childhood measures such as hand muscle strength (β: 0.21 mm3 per 100g, 95% CI: 0.04, 0.37) and sit-ups (β: 0.04 mm3 per count/10, 95% CI: 0.01, 0.08) were significantly associated with medial tibial cartilage volume, but these became non-significant after further adjustment for medial tibial bone area.

Conclusion: A number of childhood physical performance measures are significantly associated with knee bone area and cartilage volume in adulthood. The associations with cartilage volume appear to be mediated by tibial bone area. This suggests physical activity in childhood can independently influence adult knee joint health possibly through adaptive mechanisms during growth.

Disclosure: B. S. Eathakkattu Antony, None; G. Jones, None; A. Venn, None; L. Blizzard, None; F. Cicuttini, None; L. March, None; T. Dwyer, None; C. Ding, None.


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