Instability of the knee joint - experienced as a sense of the knee 'giving way' - is an important symptom of knee injury and a predisposing factor for both acute knee injuries and osteoarthritis. Despite its importance, however, not much is known about the prevalence of knee instability among athletes and its association with particular sports and occupations.

In an effort to shed more light on the problem, a team of Danish researchers embarked on a detailed questionnaire study of 339 active competitive athletes aged 14-24, who belonged to one of two sports clubs in Aarhus County.

Here are their key findings:
1. The overall prevalence of knee instability in the year preceding the study was 22%, with a much higher incidence among females (36%) than males (14%);
2. The overall prevalence of constant or recurrent instability was 14%;
3. The prevalence of absence from sport and work due to knee instability were 5% and 1% respectively.

Knee instability did not seem to be related to the type of sport preferred by the participants, whose chosen sports included football, handball, basketball, badminton, tennis, competitive gymnastics, swimming and jogging; neither was it related to weekly hours of participation in a specific type of sport or years of participation in that activity.

However, it was strongly linked with female gender, years of predominantly standing occupational work and hours of predominantly sitting occupational work per day.

The researchers point out that the observed prevalence of knee instability was considerably lower than that of knee pain among athletes, while the reported 1% prevalence of absence of work could suggest it is not a serious problem. However, the fact that only 17% of the young participants were in occupational work raised the prevalence of absence to 6%, similar to that of absence from sport.

'In conclusion,' say the researchers, 'knee instability is a commonly reported phenomenon among active athletes independent of the type and the amount of sports activity, but highly dependent on female gender, type and amount of occupational work.'

Thus preventive strategies need to be focused on female athletes, with special attention given to athletes' occupational workload.
Scand J Med Sci Sports 2001 Aug 11(4), pp233-238

Isabel Walker