Summary of results
To our knowledge, this is the first systematic review on this topic. Our aim was to improve the understanding of the relationship between type of sport and OIE in children and adolescents. The individuals included in this study were more often adolescents than children, but the articles included did not allow us to distinguish between these two groups. Whilst the reporting styles of the reviewed articles made it impossible to compare exact incidence rates, relative differences in occurrence could be studied in relation to the proportion of injuries per numbers of hours of exposure and injury site and diagnosis.
In a previous large study on 1259 school-children aged from 6 to 12 years old, in which data were collected with weekly text messages over 2.5 years, the lower extremities were generally affected more often than the upper extremities [9]. The results of our review largely confirm this finding. Specifically, our results indicate that the most commonly injured anatomical sites were the knee and lower leg.
They were two exceptions to this: handball and gymnastics. In handball the most commonly injured areas were elbow and the lower leg; they were equally frequent. In the two articles concerning gymnastics, the foot was the second most common affected area. In one article, the knee was in the first position, whereas in the other it was the lower leg.
Furthermore, our results indicated the most common diagnoses to be tendinitis/bursitis and periostitis and these were similar across all sports (when reported) but, again, no incidence estimates could be extracted.
Methodological aspects of the articles reviewed
In relation to the external validity of these results, it is not known how representative the study samples would be for children as a whole, as the articles reported on specific sport groups and there were no population-based studies. The main objective in most of the studies was to describe the musculoskeletal problems that occurred in a sports club or school, i.e. using convenience samples. A larger number of studies would probably have given a wider range of results. Low response rate could also affect the validity of data, and response rate information was provided in only five studies.
Injury was never clearly defined on its own. Instead, problems arising in relation to a sport activity would be reported if there was also a time loss for that sport, or if medical attention was required. The definition of “injury” was therefore a definition of consequences, e.g. time-loss and/or medical attention, rather than a painful condition.
Further, the overuse definition lacked a substantial pathological aspect relying mainly on the observation of gradual onset of symptoms. Bahr has already discussed this problem [7]. We propose that it would probably decrease the risk for misclassification, if at least three of the following criteria were fulfilled: repeated micro trauma, no single identifiable cause, activity exceeds tissue tolerance, and gradual onset.
Furthermore, the level of expertise differed between persons responsible for defining the injury, ranging from medical specialist to the injured individual. Depending on the definition and site of injury, it can be expected that self-reported problems might be less accurate than those obtained through a medical examination. The definition is important when comparing estimates between studies, because, as pointed out by Bahr, self-reported pain will result in higher estimates than pain with a consequence in terms of medical attention or time-loss [7].
The fact that not all diagnoses and sites of injuries were clearly reported in each article was an additional difficulty.
In sum, this area of research would benefit from a well-reasoned consensus approach to the various relevant definitions, making it possible to compare findings between studies.
Methodological aspects of our review
Relevant articles written in other languages than those included in our review may exist and their inclusion could have changed the results.
Checklists and evidence tables used for data extraction were tested for user-friendliness and adjusted in a pilot study before being used in the main study. The review was carried out independently by two reviewers, one of whom was experienced in performing systematic reviews. Because the objectives of the articles were different from ours, it was frequently necessary to discuss and interpret their texts to correlate with our checklist but the third reviewer never had to be called in for arbitration.
Discussion of findings regarding the anatomical site of OIE
In some sports, such as handball and gymnastics, the upper limb is subjected to more repetitive stress than in other sports, such as soccer and running. One could assume that it therefore should be affected at least as often as the lower limb but, generally even in these sports the lower limb was most commonly affected. Perhaps the explanation for this is that the lower limb always carries the weight of the body, which puts the lower limb in a constant stress situation. In comparison with this constant weight, other sport-associated demands on the upper body are probably much less important.
Discussion of findings regarding the diagnostics of OIE
The results of our study indicate that the most frequent diagnoses are fairly similar across sports, mainly reported as tendinitis/bursitis, and periostitis. Not surprisingly, OIE seem to occur mainly where the bodily structures are most subjected to repeated stress.