Glenohumeral Part 1: An introduction to the Anatomy, Biomechanics and the Incidence of Shoulder Injuries in Golf
Dr. Craig Davies
The shoulder complex is an often-injured area in players of all skill levels. In my experience on the PGA Tour shoulder injuries can steal a significant amount of a player’s season. The injuries can be difficult to manage and recover from if misdiagnosed and / or not respected.
The shoulder must be considered, at minimum, as a complex consisting of the humerus, scapula, thoracic spine / ribs and the cervical spine. In realty, every body part can have an impact on the development and recovery of shoulder pain from the distal phalangeal joint in the big toe to the occiput / cervical spine.
In this first shoulder section, I will focus more on the glenohumeral joint and the more common complaints associated to this area. In future sections I will consider basic assessment and management of injuries associated with the glenohumeral and scapulothoracic regions.
Shoulders are the third most frequently injured body part among professional golfers (lower back and wrist / hand) (McCarroll and Gioe). Lead shoulder injury occurs in 75% of cases (Pink 1990).
By age group the most common type of injury within the shoulder are:
Young golfers: instability / traumatic
Middle age: sub-acromial / AC disease
Older: rotator cuff and glenohumeral degeneration
Obviously these conditions can occur in any age group but they generalizations do provide a rough outline for age related pathologies.
One of the key points to consider when assessing a golfer is the phase of the golf swing resulting in their symptoms. If pain is felt in the back of the lead shoulder at the top of the up swing, tightness to the rotator cuff, posterior capsule or other pathology could be the culprit. If the back of the shoulder, upper back is uncomfortable during the follow through a rib / vertebrae interface may be the pain stimulator.
Another important scenario to consider is whether a decrease in the available rotation throughout the golfer’s body may be placing the soft tissues (muscles, ligaments and capsules) of the shoulder under unnecessary and excessive stress leading to the breakdown within the shoulder complex and the presenting symptomology. The shoulder may be the link attempting to make up for the lack of motion elsewhere and “feels” tight as it reaches its physiological end range. Attempting to increase the range in the shoulder may actually create an unstable environment if the actual pain presentation is a secondary compensatory pattern for the body mechanical limitations elsewhere.
So, is it a shoulder injury or global movement deficiency showing up as shoulder pain? The assessment of the complete athlete, even in the case of an identifiable source of pain, is paramount to their long-term rehabilitative success.
Understanding why the shoulder, or any other body part, broke down is the only way to prevent the recurrence and allow for maximal recovery of the symptomatic region.
What should not be underappreciated is the role of the latisimus in allowing proper movement and control of the shoulder. With its attachment and influence into the lumbar spine and pelvis and fascially the contralateral (opposite) leg, the latisimus can exhibit a heavy influence on shoulder mechanics.
We have and will continue to emphasize throughout this series the importance of examining the entire kinetic chain when treating a golf specific injury. This is of the utmost importance when dealing with an upper extremity issues, specifically the shoulder. As we get to the smaller joints closer to the handle of the club, we are dealing with links moving through greater and greater angular velocities, accelerations and magnitudes of motion. This will obviously increase the amount of strain on the soft tissues supporting the joints. Additionally, these joints are forced to compensate and make up for deficits in movement from the larger more central joints and muscle groups.
An example of this for the shoulder can be visualized in an example of the club head approaching the top of the take away. If there is limited movement within the hips or thoracic spine, the golfer will attempt to reach the top of their take way through an exaggerated range of horizontal adduction and flexion in the scapulothorcic (between the shoulder blade and thoracic spine / ribs) or glenohumeral (arm into shoulder blade) joints.
Understanding and recognizing the limitation in movement can be of great help to the teaching professional to tell them of the limitations in movement. Often the golf pro will work within these new limitations and shorten the swing while the athlete works to regain proper mechanics within the body. The greater the increase in the compensatory motion, the greater the likelihood of rotator cuff, AC or other injury.
The role of the shoulder in golf;
The shoulder is an area with very complex anatomy and biomechanics. Very large ranges of motion in a number of planes create an inherently unstable joint complex. This complex relies predominantly on the soft tissues surrounding the joint for stability. The bony anatomy of this joint includes the glenoid, acromion, humeral head, clavicle and sternum. Secondary bony anatomy includes the ribs, cervical and thoracic spine. If we included only the clavicle, humerus and scapula within our examination, we would still have twenty muscles that serve the three bones, with 95 sites of insertion. The soft tissues directly involved with the shoulder include the glenoid labrum, glenohumeral ligaments, acromioclavicular and coracoacromial ligaments, rotator cuff, pectoralis and scapulothoracic musculature.
The importance of the shoulder within the golf swing cannot be overstated. One of the more significant joints of the body when one considers the golf swing and at times the most limiting to consistent success and efficiency. The need for precision movement within the shoulder and all of its associated articulations should be noted. Many practitioners treat the shoulder as though it is one joint, the glenohumeral joint. This way of thinking needs to be updated. The sternoclavicular, acromioclavicular, scapulothoracic, suprahumeral and costovertebral joints most certainly deserve attention and quite often the spine and lower extremities must be considered when dealing with any pain related to the shoulder. As the shoulder has one of the most complex set of biomechanics, it is often a source of performance limitations.
A basic breakdown of the shoulder movement desired in the golf swing:
During the takeaway the lead shoulder undergoes near to maximum horizontal adduction, internal rotation and a significant amount of flexion at the glenohumeral joint and the scapulothoracic articulation requires significant protraction. The trail shoulder undergoes near maximum external rotation, abduction and flexion at the glenohumeral joint and the scapulothoracic articulation undergoes retraction and depression.
On the downswing the target side scapulothoracic articulation must allow for retraction and depression while the trail shoulder will go through protraction during the follow through.
As the golfer approaches their finishing position post-ball strike, the lead shoulder performs near maximum flexion, external rotation and abduction and the trail shoulder undergoes internal rotation, flexion and horizontal adduction. Limitations in these ranges of motion will result in unpredictable swing mechanics and decrease the efficiency and effectiveness of the swing. In addition to requiring such large degrees of motion throughout the shoulder complex, these ranges need to produce and absorb very large forces. This combination of rang and stabilization often results in overuse injuries.
Anatomy, Biomechanics and Movement:
MOVEMENTS OF THE STERNOCLAVICULAR JOINT
- Passive movements.
- Types of Movements.
- Acromial end moves as consequence of movements of the scapula
- Sternal end of clavicle moves in a direction opposite from that of the scapula.
- Protraction – scapula is retracted causing the sternal end to move forward
- Retraction – scapula is protracted causing the sternal end to move backward
- Elevation – scapula is depressed causing the sternal end to move upward
- Depression – scapula is elevated causing the sternal end to move downward
MOVEMENTS OF THE SCAPULA Types
Elevation – moving the superior border of the scapula and the acromion in an upward direction.
Depression – moving the superior border of the scapula and the acromion in a downward direction.
Upward Rotation – Moving the scapula so that the glenoid cavity faces upward.
- Increased the ranges of motion during abduction and/or flexion of the shoulder.
Downward Rotation – moving the scapula so that the glenoid cavity faces inferiorly.
- Increases range of motion during extension and / or adduction of the shoulder.
Protraction ( Abduction) – moving the scapula away from the midline
Retraction (Adduction) – moving the scapula toward the midline
MOVEMENTS OF THE GLENOHUMERAL JOINT
Movements of the shoulder joint (glenohumeral joint) usually involve moving the humerus on the scapula.
All movements are to be studied starting from the ANATOMICAL POSITION
Axis of motion
Flexion – Extension
Coronal axis through head of humerus
- Sagittal axis through humeral head
- Longitudinal axis through shaft of humerus
Types of Movements
Flexion moving the humerus forward and upward in the sagittal plane.
Extension – bringing the arm down to the side in the sagittal plane.
Hyperextension – moving the arm in the sagittal plane behind the body.
Abduction – moving the arm in the coronal plane away from the midline
90° – deltoid
180° – deltoid with upward rotation of scapula
Adduction – moving the arm in the coronal plane towards the midline.Inward Rotation – rotating the arm in a transverse plane so that the anterior surface of the bone turns inward.Outward Rotation – rotating the arm in a transverse plane so that the anterior surface of the bone turns outward.
Coordinated movements of the scapula and the humerus increasing the range of motion at the glenohumeral joint
Figure 1 SCAPULA MOVEMENTS
Retraction means the scapula is drawn towards the midline; protraction is movement away from the midline. Elevation is raising the entire scapula upwards as in shrugging ones shoulder; depression is lowering the scapula.
Figure 2 SCAPULA Rotation
Upward Rotation of the scapula involves rotating the glenoid cavity upward while moving the inferior angle laterally; downward rotation involves rotating the glenoid cavity downward while the inferior angle moves medially. Upward rotation occurs during flexion and abduction of the shoulder to increase the range of motion when the humerus moves on the scapula. Downward rotation is used to increase the range of motion of the humerus when it moves on the scapula during shoulder extension and adduction.
The clavicle is an S-shaped bone that connects the trunk to the shoulder girdle. It is a rigid structure that maintains the shoulder in a functional position in relationship to the axial skeleton and helps to allow for the varied hand positions required in sports. It presents a double curvature, the convexity being directed forward at the sternal end, and the concavity at the scapular end. The deltoid, pectoralis major, trapezius, sternocleidomastoid, and subclavius all insert or originate on the clavicle and can cause deforming forces after an injury.
The clavicle articulates with the acromion to form the acromioclavicular (AC) joint and with the sternum to form the sternoclavicular (SC) joint (figure 1: not shown). The lateral aspect of the clavicle and the medial border of the acromion form the diarthrodial AC joint. Several ligaments reinforce the joint capsule to maintain stability. The AC ligament and the capsule provide anterior-posterior and medial-lateral stability, while the coracoclavicular ligaments provide vertical stability. If the distal clavicle is prominent. Only when the coracoclavicular ligaments are completely torn is the distal clavicle prominent in a shoulder separation.
The SC joint depends on the surrounding capsule and ligaments for stability. Ligamentous structures include the SC ligament (or capsular ligament), an intra-articular disk ligament, an interclavicular ligament, and an extra-articular costoclavicular ligament (rhomboid). The SC ligament is the strongest and most important structure preventing upward displacement of the medial clavicle (4). The costoclavicular ligament is an important stabilizer if a proximal resection is necessary.