Exercise does not cause knee osteoarthritis [Sep 2001; 91-5]

Exercise does not cause knee osteoarthritis
Study Results Comment

Andrew's mother's hairdresser's friend has been known to say that the more exercise you have, the more you are likely to have knee problems when you are older. To put it bluntly, this old wife's tale is that not exercising is good for you. A new piece of quality research from Nottingham gives the lie to this [1].

Study

The dataset for the study was information from the Allied Dunbar National Fitness Survey. This was carried out in 1990-91 on roughly 200 people chosen at random from each of 30 parliamentary constituencies. This survey covered sport and exercise participation from age 14 to the date of interview. It also asked several key questions on knee injury.

Cases were selected retrospectively from people responding positively to questions about ever having arthritis, and still having it, suffering from continuous or recurrent pain in the knee, starting at over 40 years, and without pain, swelling or stiffness in wrists, hands or fingers. This corresponded closely with American College of Rheumatology criteria, and excluded inflammatory arthritis.

For each case, four age matched controls were selected.

Exposure to exercise was clearly demarcated by types of exercise more or less likely to strengthen knee joints, and specifically to regular long walks, in the periods 5-14 and 15-24 years before diagnosis, and at ages 14 to 19 and 20 to 24.

Results

There were 216 eligible cases, and 828 distinct individuals, with some controls being chosen more than once. Knee injuries before the diagnosis date were reported in 3% of cases and 0.3% of controls.

Using logistic regression analysis to interrogate this complex data set led to only one statistically significant association, that between previous knee injury and development of knee osteoarthritis. A lot of exercise at ages 20-24, and regular long walks 5-14 and 15-24 years before were significant for univariate, but not multivariate analysis (Table 1).

Table 1: Association between exercise, knee injury and knee OA in multivariate analysis

Variable	Odds ratio	p value
Walking 15-24 years before	1.5 (0.95 to 2.4)	0.08
Lot of exercise at age 20-24	1.6 (0.94 to 2.7)	0.09
Knee injury	6.7 (1.3 to 34)	0.02

Comment

This study has a brilliant discussion. It examines these results in relation to others, and sets them in place. It also is both self-critical and at the same time justifies the power of this analysis, and retrospective case series in general. There is much to be learned about methodology.

For simple souls, the message is that, by and large, exercise will not cause knee osteoarthritis in later life. The cautionary note is that not all exercises are equal, and if they cause knee injury, arthritis may well follow. Bandolier would prefer rowing or weight lifting to climbing, ice skating or skiing, where risks of other injuries are somewhat higher.

References:

AJ Sutton et al. A case-control study to investigate the relation between low and moderate levels of physical activity and osteoarthritis of the knee using data collected as part of the Allied Dunbar National Fitness Survey. Annals of Rheumatic Diseases 2001 60: 756-764.

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