An overview of the shoulder joint and some common injuries
In contact sports, the shoulder is one of the most frequently injured joints in the body.
The shoulder often takes the brunt of the force generated by the tackle in contact sports; with dislocations common in Ice Hockey, both codes of rugby, American football, Australian Rules football and Gaelic football to name but a few (Headey et al., 2007; Hrysomallis, 2013; Kaplan et al., 2005; King et al., 2010; O’Conner et al, 2016, Popkin et al., 2017).
The nature of these games as contact sports means that traumatic injury to the shoulder is common, with a high percentage of these injuries reported as dislocations. Wen (1999) reported the shoulder as the most frequently dislocated joint in the body.
Exposure to contact situations has been shown by Orchard (2003) to play a significant part in athletes missing playing and training time accordingly. Kaplan et al (2005) reported that the shoulder joint had a high tendency to be injured in American Football players with increasing exposure.
In association football, shoulder dislocations sustained by goalkeepers are frequent and well-reported; but literature addressing other shoulder injuries of any type and particularly injuries to outfield players is scarce. Longo et al (2012) studied shoulder injuries in association football but were unable to differentiate between goalkeepers and outfield players due to the lack of comparative literature.
Only 80 shoulder injuries were recorded by Ekstrand et al (2011) in the UEFA study of 2008 in which 4483 injuries were audited in total; the vast majority of these being to the lower limb (87%). Earlier work by Hawkins et al (2001) in England, underpinned Ekstrand’s findings.
Basic Anatomy
The shoulder itself is typically referred to as the glenohumeral joint (GHJ), which is the most mobile joint in the human body and also the most unstable (Richards, 1999). It is a ball and socket joint formed by the articulation of rounded part of the bone of the upper arm known as the humeral head, and the socket of the scapula – or shoulder blade - known as the glenoid fossa.
The instability of the GHJ arises as a result of the small contact area between the glenoid cavity on the scapula and the humeral head, which allows movement to take place in all directions, leading to significantly increased injury risk. Rowe & Zarins (1981) provided the classic and often-referred to description of the shoulder joint by likening the relationship between the humeral head and the glenoid cavity to a seal balancing a ball on the end of its nose.
Anatomically, static stabilisation of the shoulder arises from the glenohumeral ligaments, the articular capsule and the fibrocartilaginous glenoid labrum, which effectively deepens the glenoid cavity by 50% (Park et al, 2002). Additionally, negative intra-articular pressure within the glenoid labrum contributes to glenohumeral stabilisation by creating a relative vacuum (Wilson and Price, 2009).
Dynamic stability of the shoulder is provided by the rotator cuff muscles through their ability to position the humeral head in the glenoid fossa and maintain its position during activity and rest, together with the functional restraints provided by the individual glenohumeral ligaments and the scapular and biceps muscles (Seade and Jossey, 2008).
Injury mechanics
Injuries to the shoulder can comprise of bony injuries, traumatic dislocations, ligamentous sprains of glenohumeral ligaments, soft-tissue muscle strains and tears including injuries to the rotator cuff, tendinitis, tendinopathy, and injuries to the joint capsule.
In association football, injuries to the shoulder constitute a relatively small number of injuries by comparison to the lower limbs. Shoulder injuries in football to outfield players often occur as the result of landing after a fall, and in general, this might be because most outfield players are often unprepared for the impact.
Volpi (2006) argues that goalkeepers are much better than outfield players at learning how to hit the ground safely, thus giving themselves the minimal risk of ground-contact injuries and this would partially at least help to account for the variances in injury patterns between goalkeepers and the rest of their teammates.
Statistically, it has been shown that goalkeepers make ground contact 200 times per week through training and playing and this has enabled them to develop better landing techniques as a result.
As with most joints, though, injuries can arise in several ways. This can either be through direct contact or a fall on the outstretched arm or point of the shoulder or as a combination of both. Dislocations are frequent and are usually the result of forced abduction together with external rotation.
Direct contact injuries can occur through the arm being pulled or twisted; as in the so-called and illegal “chicken-wing tackle” in rugby league, while non-contact injuries are often the result of a sudden loss of control such as in weight-lifting for example, when the athlete loses control of the overhead bar.
Additionally, injuries can be the result of overuse – or underuse – mechanisms; and symptoms of one kind of injury or condition can lead to another. A typical example of this is when an inflammatory injury to the rotator cuff leads to a reduced range of movement and this then develops into secondary adhesive capsulitis – aka the familiar "frozen shoulder".
Summary
To relate all the above information to association football, further research into common and less frequent shoulder injuries will be essential. Piero Volpi (2006) discusses this in his excellent book, Football Traumatology (updated 2015), and stresses that just because certain injuries are less prevalent than others, these do occur, albeit only in lesser numbers.
The topic of shoulder injuries is huge and there are many websites devoted solely to the management and treatment of these. It is not the intention of this website to simply replicate the contents of other specialised websites and consequently the focus here will be on the practical aspects of shoulder injury management, drawing on examples from professional sport.
Further shoulder content will be added shortly…