A new study by radiologists found that middle-aged men and women who do lots of exercise, and particularly high impact activities like running
and jumping, may be unknowingly causing damage to their knees and putting themselves at greater risk of developing osteoarthritis. By implication,
low impact activities like swimming and cycling may protect damaged and healthy joints they said, although further research is needed to confirm
The study was the work of Christoph Stehling and colleagues, and is being presented Monday at the 95th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA), taking place from Nov 29 to Dec 4, in Chicago.
Stehling is a research fellow in the Department of Radiology and Biomedical Imaging at the University of California, San Francisco (UCSF) and a resident in radiology with the Department of Clinical Radiology at the University of Muenster in Germany.
Osteoarthritis, the most common form of arthritis, affects some 27 million American adults, estimates the US Centers for Disease Control and Prevention (CDC). The disease is degenerative and affects the joints, causing pain, swelling and stiffness.
Osteoarthritis has three features: damaged cartilage (the strong, smooth lining that allows joints to move easily without friction), bony growths around the edge of joints, and mild inflammation (synovitis) of the tissue surrounding the affected joint.
Stehling told the media that:
"Our data suggest that people with higher physical activity levels may be at greater risk for developing knee abnormalities and, thus, at higher risk for developing osteoarthritis."
For the study, Stehling and colleagues analysed data of 100 men and 136 women aged 45 to 55 taking part in the National Institutes of Health Osteoarthritis Initiative (which they referred to as the "OAI incidence cohort").
None of the participants reported experiencing knee pain before enrollment and their weight was in the healthy range.
The researchers categorized the participants into low, middle and high activity, depending on their responses to a questionnaire that assessed their physical activity according to the Physical Activity Scale for the Elderly (PASE). PASE yields a score based on activity type and time spent doing it.
The participants were thus put in one of three groups: low activity (PASE score 27 to 155), middle activity level (PASE 156 to 230) and high activity (PASE 231 to 409).
A middle-aged person who spends several hours a week walking, doing sport and other exercises, plus yard work, heavy gardening and household chores would have a high PASE score.
Two of the researchers, who are experts in musculoskeletal radiology, analyzed MRI images of the participants to assess severity of any cartilage, meniscal and ligament damage, or other abnormalities, in the right knee.
The results showed that:
- 47 per cent of the participants had meniscal lesions.
- 74.6 per cent had cartilage lesions.
- 40.3 per cent had bone marrow edema.
- 17 per cent had ligament lesions.
- Incidence of abnormalities went up in line with PASE activity level (low, medium, high).
- Grade of cartilage lesions also went up with PASE activity level.
- Presence of other knee abnormalities was also significantly linked to presence of cartilage defects.
- Abnormalities were linked solely with activity levels and were not age or gender specific.
"Middle-aged non-symptomatic individuals from the OAI incidence cohort had a high prevalence of knee abnormalities including cartilage and meniscus lesions. Individuals with higher PASE showed a significantly higher number and grade of knee abnormalities."
"These results suggest that subjects with higher physical activity levels may be at greater risk for cartilage and meniscal abnormalities and thus higher risk for developing Osteoarthritis (OA)," they added.
Stehling said that knee abnormalities went up in line with level of physical activity, and "in addition, cartilage defects diagnosed in active people were more severe".
He said the findings also showed that some activities carry a greater risk of knee damage over time.
"This study and previous studies by our group suggest that high-impact, weight-bearing physical activity, such as running and jumping, may be worse for cartilage health", said Stehling.
"Conversely, low-impact activities, such as swimming and cycling, may protect diseased cartilage and prevent healthy cartilage from developing disease," he added, suggesting more studies were now needed to compare the effect of low and high impact activity on disease progression.
"Subjects with Higher Physical Activity Levels Have More Severe Focal Knee Lesions Diagnosed with 3T MRI: Analysis of the Non Symptomatic Incidence Cohort of the Osteoarthritis Initiative."
Presented by: Christoph Stehling; Abstract Co-Authors: Nancy Lane, Michael Nevitt, Charles McCulloch, and Thomas Link.
Radiological Society of North America, 95th Scientific Assembly and Annual Meeting, Nov 29 - Dec 4, 2009, Chicago.
Code:SSC10-02, Session: Musculoskeletal (Knee Disorders).
Written by: Catharine Paddock, PhD