in generalized ligamentous laxity , the range of motion across various joints in an individual is increased compared to the mean range of motion in the general population ( 1 ) .
although this could occur as a result of genetic disorders affecting the connective tissue , in most individuals there is no genetic aberrancy and it exists in isolation ( 2 ) .
the prevalence of generalized ligamentous laxity varies among different races from 5% to 57% of the general population ( 3 ) .
it is well known that generalized ligamentous laxity is implicated in various musculoskeletal injuries , especially in the lower extremities , such as cruciate ligament injuries , patellar instability , and ankle injuries ( 4 , 5 ) .
although generalized ligamentous laxity is a predisposing factor for shoulder instability ( 6 ) , to the best of the authors knowledge no study has investigated the role of generalized ligamentous laxity in acute and chronic shoulder injuries in athletes .
this study aimed to determine whether generalized ligamentous laxity can be a predisposing factor for acute and chronic shoulder injuries in athletes .
this cross - sectional study was conducted from april to october 2015 . to obtain a representative sample of athletes with shoulder injuries
, we sought all athletes who had sustained shoulder injuries in hamadan province in iran over the previous three years according to the documents of the local branch of the iranian federation of sports medicine in hamadan province .
all the relevant data were recorded , including demographic information , type of sport , duration of sporting activity , and the beighton score for generalized ligamentous laxity ( table 1 ) .
our inclusion criteria were being 17 - 37 years old and having a history of sports activity for at least six months ( if there was a shoulder injury , then the requirement was at least six months of sports activity before the injury ) .
the exclusion criteria were having any deformity or disorder that interfered with the beighton score assessment and a lack of documents proving at least six months of regular sports activity .
several athletes were excluded , mainly because of a lack of documentation proving sports participation . using a sampling formula for cross - sectional studies where  = 0.05 , d = 0.065 , and p ( ligament laxity prevalence according to other studies ) = 0.15 ,
all the volunteers signed a consent form to confirm their participation in the study , and the study was approved by the ethics committee of hamadan university of medical sciences ( no . :
ir.umsha.rec.1395.101 ) we considered generalized ligamentous laxity as point 4 or more of the beighton score and divided all the participants into two groups : the participants in group a had ligamentous laxity (  with ligamentous laxity  ) and those in group b did not (  without ligamentous laxity  ) .
any acute or chronic shoulder injuries and functional issues among the participants were also assessed according to the standard farsi ( contemporary persian ) translation of the quickdash measure .
a total of 118 volunteer athletes participated in our study , which included 32 athletes with shoulder injuries and 86 athletes without shoulder injuries .
they were divided into two groups according to the beighton score : group a ( with ligamentous laxity ) consisted of 43 participants and group b ( without ligamentous laxity ) consisted of 75 participants .
we then compared the following factors between the two groups : acute shoulder injury , chronic shoulder injury , shoulder instability , chronic shoulder pain , and dash scores ( table 2 ) .
a statistical analysis was carried out using the statistical package for social sciences ( spss ) version 20 software ( spss inc . ,
chicago , il ) . the chi - squared test was used to analyze the effect of the generalized ligamentous laxity on the nominal scale values , namely chronic shoulder pain , and chronic and acute shoulder injuries .
spearman s test was used to analyze the generalized ligamentous laxity effect on the last value ,  successful return to sports activities ,  for which the dash score was ordinal .
first , we evaluated the relationship between ligamentous laxity and chronic shoulder pain ( table 3 ) .
sixteen participants ( 37.2% ) in group a and 13 participants ( 17.3% ) in group b suffered from chronic shoulder pain ( p = 0.016 ) .
we then evaluated the number of chronic shoulder injuries in both groups ( table 4 ) .
thirteen participants in group a ( 30.2% ) and 11 participants in group b ( 14.6% ) had chronic shoulder injuries , which was statistically significant ( p = 0.032 ) .
with respect to acute shoulder injuries , 11 participants in group a ( 25.5% ) and 19 participants in group b ( 25.3% ) had chronic shoulder injuries ( table 5 ) .
we then assessed upper limb function using the quickdash measure ( table 6 ) and found that there was a significant difference between the functional status of the two groups ( p = 0.030 ) .
finally , we compared the history of acute and chronic instability between the two groups based on dislocation documentation or a history of shoulder pain with at least two positive clinical tests for instability ( table 7 ) .
eleven participants in group a ( 25.5% ) and five participants in group b ( 6.6% ) had instability , which was significant ( p = 0.004 ) .
the shoulder joint gets injured frequently in sports like volleyball , handball , swimming , basketball , and overhead sports , and an abnormal increase or decrease in range of motion is an important factor in sports injuries involving the shoulder ( 7 ) .
generalized ligamentous laxity refers to an increased range of joint motion compared to that of the general population .
its prevalence is 5% - 15% but varies among different race groups , with an incidence as high as 57.3% among africans ( 1 , 6 ) .
although there is no standard for defining ligamentous laxity , there are several clinical scoring systems for measuring joint laxity in individuals and populations .
the beighton score is considered an excellent method for screening generalized ligamentous laxity ( 8 , 9 ) .
bin abd razak et al . evaluated generalized ligamentous laxity in the musculoskeletal injuries of 100 young patients in a primary care center for comparison with a healthy control group ( 1 ) .
they found that the individuals who had musculoskeletal injuries were 3.35 times more likely to have generalized ligamentous laxity compared to healthy people .
several studies have demonstrated the relationship between generalized ligamentous laxity and sports injuries in the lower extremities , including cruciate ligament injuries ( 4 ) and patellar dislocation ( 5 ) .
found a significantly increased risk of knee joint injury among hypermobile participants who played contact sports ( 10 ) .
notwithstanding , little evidence exists regarding the relationship between generalized ligamentous laxity and shoulder injuries .
studied generalized ligamentous laxity and increased external rotation of the shoulder as a predisposing factor for primary shoulder dislocation in young , healthy individuals .
they found that men with shoulder dislocation were 6.8 times more likely to have generalized ligamentous laxity ( 6 ) . to the best of our knowledge
, no study has investigated a range of shoulder injuries in athletes with or without ligamentous laxity .
hence , we evaluated the relationship between generalized ligamentous laxity and various shoulder injuries in athletes who had participated in sports activities for at least six months .
the athletes with generalized ligamentous laxity had more chronic shoulder pain , chronic shoulder injuries , shoulder instability ( acute and chronic ) , and less functionality according to their dash scores compared to the athletes without generalized ligamentous laxity .
interestingly , there was no difference in the number of acute shoulder injuries between the two groups .
this was because we considered fractures around the shoulder to be acute injuries in the study .
if we had omitted fractures in both groups , the difference in acute injuries would have been significant .
the strength of our study was the evaluation of all the volunteer professional athletes in our province who had participated in at least six months of regular sports activity , including professional athletes with shoulder injuries . since the treatment of injured athletes is the responsibility of the federation of sports medicine in iran , this federation had a complete list of all the injured athletes in the province .
the limitation of our study was that we only evaluated athletes in one province of iran .
although hamadan province is ethnically diverse and includes most iranian ethnic groups ( azeri , kurd , lur , and fars ) , and parallel research results will thus be quite compatible with the current research findings , it is suggested that the same study be conducted in different provinces of iran with a greater number of athletes .
a sports injury can be influenced by the athlete s level of professionalism . although we excluded athletes who had participated in professional sports activities for less than six months , it is not clear if their knowledge and ability to prevent sports injuries would be the same as those with more experience .
this study highlights the importance of having screening programs in athletic clinics , sports clubs , and sports offices at high schools and universities to identify individuals with generalized ligamentous laxity , and emphasizes the need for physicians and surgeons to practice prophylactic measures .
there may be a role for shoulder - specific proprioceptive and strength training protocols for shoulder injuries in individuals with generalized ligamentous laxity who participate in high - risk sports , especially contact sports .
 backgroundgeneralized ligamentous laxity is defined as an increased range of joint motion compared to that of the general population . 
 it is a predisposing factor for sports injuries , especially in the lower extremities . 
 nevertheless , there is little evidence about the relationship between generalized ligamentous laxity and sports injuries in the upper extremities.objectivesto evaluate the relationship of generalized ligamentous laxity with acute and chronic shoulder injuries in athletes.patients and methodsour study comprised 118 volunteer athletes with a history of at least six months of sports activities and a shoulder injury in the three years prior to participation in our study . 
 the athletes were divided into two groups : those with or without generalized ligamentous laxity . 
 acute and chronic shoulder injuries , shoulder pain , shoulder instability , and functional status assessed via the quickdash measure were determined and compared between the two groups . 
 a p value of less than 0.05 was considered significant.resultsgroup a ( with ligamentous laxity ) consisted of 43 participants ( 36.4% ) and group b ( without ligamentous laxity ) consisted of 75 participants ( 63.6% ) . 
 the athletes in group a had more shoulder pain ( p = 0.016 ) , chronic shoulder injuries ( p = 0.032 ) , and shoulder instability ( p = 0.004 ) , and less functionality ( p = 0.030 ) than those in group b. if fracture were not considered an acute injury in both groups , the athletes with generalized ligamentous laxity would have had more acute shoulder injuries.conclusionsgeneralized ligamentous laxity is an important predisposing factor for acute and chronic shoulder injuries in athletes . prescreening programs for beginners and rehabilitation shoulder programs for sports athletes at high risk are strongly recommended . 