The impact of age and gender with respect to general joint laxity, shoulder joint laxity and rotation : A study of 9, 12 and 15 year old students

Abstract: The overall aim of this thesis was to study the natural development of general joint laxity, shoulder joint laxity and shoulder joint rotation in young students, and compare these to age-matched competitive swimmers to detect possible discrepancies between these groups. A further aim was to evaluate the clinical examination techniques used whether they correlate to each other in search of better understanding and interpretation of achieved measurement results. Material Forty-eight randomly selected schools participated in this Swedish nation-wide research study ( The School project 2001 ) with a total of 1846 students aged 9-15 included. Data concerning these subjects are reported in study I-III. An additional study group of 120 competitive swimmers, aged 9 and 12 year, were included and compared to the previously described group. Data concerning these subjects are reported in study III. Out of the original 1846 students, 156 of ages 12 and 15 years participated in a follow-up examination in 2004. A geographic selection was made for practical reasons. Data concerning these subjects are reported in study IV. Methods General joint laxity was scored according to Beighton. Anterior, posterior and inferior shoulder joint laxity was assessed with the drawer test and the sulcus sign, respectively. Shoulder joint rotation was measured with a Myrin OB goniometer. One and the same examiner (AJ) performed all tests in the same standardized manner both in 2001 and 2004. Results General joint laxity: A cut-off point scheme was designed by Jansson et al and differed with respect to age and gender in 2001 and was confirmed in 2004. Girls had a higher degree of general joint laxity compared to boys and male competitive swimmers had a higher degree compared to their references. Nine year old female competitive swimmers had a lower degree of general joint laxity compared to their references. The individual differences between 2001 and 2004 showed only minor changes. Shoulder joint laxity: Fifteen year old boys had a lower anterior and posterior laxity compared to girls. No significant difference was seen between competitive swimmers and their references. The individual change, over three years, showed a decrease in anterior laxity in boys. Shoulder joint rotation: Girls had higher external rotation compared to boys at the age of 12 and 15 years. Shoulder joint rotation was noted as lower in all competitive swimmers at the age of 12 years compared to their reference group. Fifteen year old students had decreased their shoulder rotation at follow-up. Conclusion Based on this study of Swedish students and competitive swimmers, the degree of general joint laxity and shoulder joint rotation is specific in terms of age, gender and sports participation. Shoulder joint laxity, however, was found to be only age and gender specific and were not associated with general joint laxity. The scheme for cut-off points regarding general joint laxity was gender and age dependent and confirmed at the three year followup. There were only minor changes in general joint laxity and shoulder joint laxity at followup, but a majority of students had a decrease in shoulder joint rotation over the same time period.