Shoulder instability and Rotator cuff related shoulder pain (RCRSP) FAQ
Shoulder pain is the 3rd most common musculoskeletal condition seen in primary care1, affecting up to 50% of the population each year2. Sadly, it has the greatest impact on physical and mental quality of life out of any musculoskeletal condition3. 1 in 4 people experience recurrent shoulder pain4 and up to 40% of new cases persist after 1 year5. Fortunately, accurate diagnosis and appropriate physiotherapy management has been shown to be effective in improving pain and function6.
Today we’ll be focusing on 2 very common causes of shoulder pain in the athletic and general populations: Rotator cuff related shoulder pain (RCRSP) and shoulder instability.
What is RCRSP and shoulder instability?
RCRSP refers to pain arising from the rotator cuff muscles-tendon unit and sub-acromial bursa of your shoulder. This encompasses a variety of conditions such as subacromial bursitis, rotator cuff tears and tendinopathies. The rotator cuff muscles are the most commonly affected structures in shoulder pain presentations, involved in 80% of cases7.
Shoulder instability refers to excessive movement of the humeral head on the glenoid, resulting in pain or apprehension. People may experience fear and sensations of instability with certain movements. Instability can be categorised according to the direction of instability, mechanism of injury (traumatic or atraumatic), and degree of structural or muscle patterning deficits.
Why is shoulder stability important?
The shoulder is a ball and socket joint formed by the head of the humerus (ball) and the glenoid (socket). The glenoid cavity is small and shallow relative to the humeral head, likening the joint to a golf ball sitting on a tee. This enables us to move our shoulder through great ranges of motion, giving us the capacity to reach overhead, behind our back and out to the side. Due to the lack of bony congruence, the shoulder relies heavily on surrounding soft tissues such as the rotator cuff muscles, labrum, joint capsule and ligaments for stability.
What are the rotator cuff muscles and how do they contribute to stability?
The 4 rotator cuff (RC) muscles arise from different aspects of the shoulder blade (scapula) and attach to the humerus. They merge and blend in tightly with the joint capsule, which is further reinforced by the labrum, coracohumeral and glenohumeral ligaments. The labrum is a fibrocartilaginous rim surrounding the glenoid that deepens the socket, providing extra stability.
Image 1: Anatomy of the glenohumeral joint: bony, muscular and capsuloligamentous restraints
All RC muscles are active whenever we lift our arm8, preventing excessive movement of the humeral head on the glenoid. They do not function in isolation, but work in symphony with the sling of muscles attaching to the scapula. These periscapular muscles function to position and orientate the scapula on the thorax to increase freedom of movement. Together, the dynamic and active stabilisation provided by the rotator cuff and scapula complex enables us to load our shoulders in vulnerable positions. This gives us the ability to perform high level activities such as butterfly swim-stroke, snatching loaded barbells overhead, and high speed throwing.
Image 2: The shoulder complex is capable of withstanding high loads in extreme ranges of motion
Now that we have established a bit of background behind these 2 conditions, let’s dive in to some questions specific to RCRSP…
What are the causes and risk factors for RCRSP?
Although the definition of RCRSP relates to pain originating from the rotator cuff and subacromial bursa, it is a multifactorial condition influenced by far more than just structural pathology. Certain factors make people more susceptible to RCRSP and are important considerations when managing this condition:
The biggest risk factor for sustaining a RC tear is age, with rates increasing dramatically after the age of 509. This may be partly explained by a combination of age-related structural and biochemical changes within the RC tendons. Surprisingly, you are twice as likely to have an asymptomatic RC tear than a tear WITH pain as you advance past 60 years of age9.
We all know that excessive loading that exceeds our shoulder’s capacity can cause sensitivity and pain. People in occupations or participating in sports that require repetitive overhead movements are at greater risk of developing RCRSP through overuse10,11.
However, underloading the shoulder can be just as detrimental to shoulder health and rehab outcomes12. It is known that both overloading and underloading have a catabolic effect on tendons, reducing its capacity to withstand load.
Smoking, obesity and metabolic syndrome promote systemic inflammation which is understood to have negative implications on tendon health and healing13, 14, 15.
External rotation and abduction strength deficits have been frequently reported in people with RCRSP15. However, it is important to note that these strength deficits are not correlated with shoulder pain or disability16.
Certain genes have been linked to the development of RCRSP, and it has been found that siblings are at two time more likely to develop full thickness RC tears than spouses17.
Physio or surgery for RCRSP?
Non-operative conservative management (i.e. physiotherapy) should be the primary intervention for treating RCRSP18. 75% of people with atraumatic full thickness rotator cuff tears achieve good long-term outcomes with physiotherapy19. Exercise has been shown to improve shoulder pain and function just as effectively as surgical treatments in both the short and long term20. In fact, 75-80% of people with atraumatic full thickness RC tears can avoid surgery by engaging in a 12-week exercise program21. Therefore, a minimum trial of at least 3 months physiotherapy should be performed before considering surgery, especially for those with atraumatic tears. Staying patient during the initial trial is important as it takes approximately 12 weeks for significant improvements to be noticed22. Avoiding surgery in this time will significantly reduce the odds of having surgery later down the track21.
What about surgery?
Surgical management for RCRSP usually involves either subacromial decompression surgery (SADS), rotator cuff repair (RCR), or both.
Surgical opinion should only be considered for very select populations including:
- People under the age of 65 years with symptomatic, traumatic, moderate-large full thickness tears that want to return to high level sport23
- those who continue to experience persistent high levels of pain and disability after a sustained trial of physiotherapy24, 25
SADS involves excising the bursa or part of the acromion (acromioplasty) to increase the size of the subacromial space. In theory, this is meant to reduce subacromial impingement of the painful RC tendons and bursa under the roof of the shoulder. The efficacy of this surgery has since been questioned, with studies demonstrating no clinically significant difference between SADS and a placebo surgery26,28. Similarly, long term studies20,27,28 have found no significant difference in shoulder pain and function between groups that i) perform exercises in isolation, compared to ii) groups performing the same exercise program after surgical intervention.
Re-rupture rates following rotator cuff repair surgery are relatively high29,30,31. Research has found that repair surgery does not stop the progression of tears and does not provide superior long term outcomes compared to non-surgical groups32. In light of this evidence, repair surgery should only be considered for people with large traumatic full thickness tears that want to return to sport quickly.
What about injections?
Corticosteroid injections (CSI) are commonly prescribed by GP’s for RCRSP, with almost 20% of presentations referred for CSI33. Although they may provide small and temporary relief (<3 months), they cannot alter the natural course of RCRSP and may increase the risk of future full thickness tears34.
Despite the promise of platelet rich plasma injections, a randomised control trial has shown they are no more effective than a placebo injection in reducing pain and improving function35. Furthermore, they are associated with greater risk of adverse events compared to placebo injection35.
Common misconceptions about RCRSP:
But my scan says I have a rotator cuff tear… surely I will require surgery to fix it!?
Rotator cuff tears are common findings in people without shoulder pain or disability36. A Cochrane review (considered to be the gold standard in evidence) stated that surgery may not improve shoulder pain or function compared with exercise therapy in small to medium atraumatic degenerative RC tears37. Another review concluded that SADS is no better than exercise or placebo and should not be offered unless a sustained trial of physio has been attempted38.
My rotator cuff tendons get impinged when I lift my arms and that is what’s causing my pain.
Subacromial impingement has been widely accepted as the primary cause of shoulder pain. The theory behind this belief is that the rotator cuff tendons become pinched between the humerus and acromion when we raise our arm. Acromioplasty surgery was invented by Dr Charles Neer to treat shoulder based on this concept, and is still used widely today despite clear evidence proving it is no more effective than placebo surgery26,28.
This theory is being put to rest by research looking into the relationship between subacromial space (distance between acromion and humerus) and shoulder pain. It has been shown that impingement is a normal physiological occurrence in people without shoulder pain39. A systematic review and meta-analysis found no correlation between acromiohumeral distance and pain or disability40. The authors also pointed out that improvements in pain and function in those with RCRSP do not correspond with relative increases in subacromial space40. Lawrence et al (2017)41 found the size of this space is not significantly different between symptomatic and asymptomatic shoulders as we raise our arms into abduction.
My shoulder pain is due to the RC tear on my scan
Rotator cuff tear size is not a predictor of pain42,45 or disability43,45. Similar to other body regions like the lumbar spine, pathological findings on imaging do not correlate with pain44. Other factors are far more important in predicting pain and disability. These include fear of movement, low self efficacy46,47 (self-belief in our abilities) and poor expectations of conservative treatments45,46,47. Whether or not this is due to lower exercise adherence or physiological unloading of the shoulder, it is safe to say that people with high self-efficacy and expectations of recovery have far better outcomes47. This rings true even if they present with greater levels of baseline pain and disability47.
What can I do to improve my prognosis?
Engaging in a structured, progressive shoulder strengthening exercise program for a minimum of 12 weeks is highly likely to provide good functional outcomes18,19,21,22. Physiotherapy advice on activity modification and how to deal with flare ups or manage symptoms is important throughout this process. Staying positive, patient and trusting in the process (and your shoulders ability) is key. Addressing modifiable factors such as limiting alcohol consumption, weight loss and improving diet and sleep can assist in the natural healing process.
Shoulder instability and dislocation FAQ:
What is the difference between a subluxation and dislocation?
Subluxation and dislocation are clinical signs of shoulder instability and relate to the degree of translation of the humeral head on the glenoid. Dislocation occurs when the humeral head comes all the way out of the socket, so it does not make contact with the glenoid surface. These usually require a formal reduction to relocate the joint back into place, however, can spontaneously reduce in some cases. A subluxation on the other hand occurs when the humeral head partially comes off the glenoid but there is still contact between the two articulating surfaces. It can be graded according to the amount of contact area between the humeral head and glenoid, e.g. 50% subluxation.
What causes shoulder instability and dislocation?
As we have already touched upon, the shoulder joint is a highly mobile joint that relies heavily on passive and active restraints. It is the most commonly dislocated joint in the body. Like RCRSP, is a frustrating injury that may recur and limit quality of life48. Deficits in muscle function and structural integrity (active and passive restraints) around the joint underpin shoulder instability, increasing the risk of dislocation.
There have been a number of different classification systems developed to provide clarity on the cause, diagnosis and management of instability. These include the FEDS and Stanmore classification systems.
The FEDS system bases classification on:
- Frequency of instability episodes: either a once off ‘solitary’ episode, occasional episodes (2-5), or frequent episodes (>5)
- Aetiology: whether the instability was caused by a traumatic incident or not
- Direction of instability: whether the shoulder is unstable anteriorly, posteriorly, inferiorly, or a combination (multidirectional instability)
- Severity of instability: whether instability episodes involve frank dislocation that require formal reduction, or subluxations that automatically reduce (come back into the socket without manual force).
The Stanmore classification categorises shoulder instability into 3 distinct groups:
- Type 1: associated with a significant traumatic event resulting in structural deficits and significant pain. These include glenoid fractures (Bony Bankart lesion), labral or capsular tears (soft tissue Bankart lesions) or humeral head fractures (Hill Sach’s lesion). They usually present as sporting injuries or a fall onto an outstretched hand (FOOSH).
- Type 2: is referred to as atraumatic structural instability. Existing structural abnormalities such as Bankart lesions, labral tears, capsular insufficiency or large rotator cuff tears contribute to instability. Anterior capsule laxity is not uncommon in this group, often due repetitive microtrauma in overhead sports such as baseball. Repetitive forced end range abduction and external rotation can result in superior labral tears (SLAP) and stretching of the anterior capsule, predisposing these athletes to instability.
- Type 3: Unlike the previous 2 shoulder groups, structural damage is not a key feature in type 3 shoulders. Type 3 presentations are underpinned by muscle patterning deficits, whereby the muscles around the shoulder are not working in unison to stabilise the joint. This poor coordination of muscle activation and recruitment can result in shoulder instability. Dislocations in this group occur without any significant trauma, and are often associated with very minimal pain.
People can progress from a type 1 to 2 to 3 shoulder whereby structural lesions after significant injury can lead to secondary dislocations in the absence of trauma. Over time, pain inhibition and compensatory movements may lead altered muscle patterning characteristic of a type 3. The same principle can be applied in the opposite direction whereby multiple dislocations in a type 3 shoulder leads to structural pathology over time, resulting in atraumatic type 2 instability.
On episode #182 of the Physical Performance Show, physiotherapist and S&C specialist Adam Meakins explored perhaps the most simple and practical classification system: shoulders that are torn loose, worn loose or born loose.
- Torn loose shoulders: analogous with type 1 shoulders under the Stanmore system, involve traumatic lesions to the stabilising structures of the shoulder joint (glenoid, labrum, ligaments, capsule, humeral head).
- Born loose shoulders: are predisposed to instability through congenital abnormalities affecting the structural integrity of the shoulder. The role of natural anatomic variations such as glenoid orientation, and connective tissue disorders will be discussed in the next section.
- Worn loose shoulders: present without history of significant trauma. These shoulders can develop over time in people that are born loose. Recurrent instability episodes in this group may lead to rotator cuff, labral or capsuloligamentous changes that compromise shoulder stability. Repetitive microtrauma from demanding overhead athletic activities can also result in such changes.
Who are more likely to get shoulder dislocations?
Males are approximately 2.5x more likely to get shoulder dislocations than females49. In particular, males in the 16-20 years old age bracket have the highest rates of dislocations49, potentially due to more risk-taking behaviours. Interestingly, the incidence of dislocation significantly increases in women over the age of 50, but this trend is not observed in men49. The majority of shoulder dislocations are seen in the active population and are due to sporting injury50, with anterior dislocations being the most common51.
Given that shoulder dislocations can compromise the structural integrity of the shoulder, it is of no surprise that history of a previous dislocation is a big risk factor for future episodes52. Interestingly, prior dislocations have been associated with greater risk on the contralateral side53. Contribution from intrinsic factors such as bilateral altered muscle activation and ligament laxity characteristic of “born loose” shoulders are likely explanations.
The orientation of the glenoid in relation to the body can increase the risk of certain types of dislocations. An anteverted glenoid (one that faces anteriorly) predisposes the shoulder to anterior instability/dislocation54. Conversely, a retroverted (posteriorly facing) glenoid may increase the likelihood of posterior dislocations55.
Conditions affecting connective tissue integrity such as generalised joint hypermobility, Marfan’s and Ehlers Danlos syndromes may predispose people to instability and recurrent dislocations56,57. Patients with these conditions are most likely to present with recurrent dislocations without any significant pain or traumatic event. The Beighton score for hypermobility is a quick and easy tool that can screen for such connective tissue disorders.
What is the difference between anterior and posterior dislocations?
Anterior dislocation occurs when the shoulder is forced into excessive abduction, external rotation and extension causing the humeral head to translate forward out of the socket. Classic mechanisms of injury include falling onto an outstretched hand (FOOSH) with the arm out by the side, blocking a basketball shot or tackling in rugby. Anterior dislocations are associated with damage to the anterior glenoid and labrum (bony and soft tissue Bankart lesions) and humeral head compression fractures (Hill Sachs lesions). These injuries occur when the humeral head makes contact with the glenoid labrum as it is forced out of the socket anteriorly.
Image 3: Classic anterior shoulder dislocation mechanisms of injury
Posterior dislocations are far less common, accounting for less than 5% of shoulder dislocations58. They occur when the arm is forced into flexion, adduction and internal rotation. Such mechanisms of injury include falls directly onto the elbow or seizures and electrocutions that cause violent contraction of the shoulder internal rotators59. These dislocations are associated with posterior labral and capsular damage when the humerus is forced posteriorly out of the socket.
What are the odds of re-dislocating my shoulder?
A systematic review by Wasserstein et al found that overall rate for recurrent instability across all ages is 21%61. However, the risk of recurrence is highly dependent on a number of factors:
- Age: risk of recurrent dislocations is inversely proportionate to age at the time of the initial dislocation60,61, with the exception of females over the age of 5061. Therefore, the younger you are when you first dislocate your shoulder, the more likely you are to sustain a second.
- Time from initial to subsequent dislocation is another know risk factor60. It has been shown that 90% of redislocation occur within the first two years of the primary dislocation62.
- Young males have significantly greater chances (up to 80%) of recurrent instability after dislocation61,62 , especially those who are highly physically active63,64 .
- The presence of a Bony Bankart lesion64 or joint hyperlaxity60 are associated with increased risk of recurrent instability.
Physiotherapy or surgery for dislocations?
When it comes to shoulder dislocations, the evidence clearly distinguishes between surgical and non-surgical candidates.
Surgery provides statistically better outcomes for young athletes after primary (first time) traumatic dislocation that want to return to high level shoulder demanding sports quickly65-69. Criterion indicators that surgeons look out for when considering intervention include the presence of a significant bony Bankart lesion, apprehension and participation in contact sports69. Although early surgical stabilisation provides reduces the risk of recurring instability and improves return to sport outcomes in active people under the age of 30, it does not provide any advantage over conservative management when it comes to everyday function and quality of life65,68,70.
Physiotherapy is highly recommended for almost all other instability presentations, even those with first time traumatic dislocations. This means if you are older than 25, do not participate in high level contact or upper limb demanding sports, and don’t have significant structural pathology, physiotherapy is likely to provide outcomes just as good68
It is already understood that people can have completely normal shoulder function and no pain despite labral and rotator cuff tears44. Improving strength and coordination of the active stabilising muscles around the shoulder can compensate for deficits in structural integrity such as labral tears. Furthermore, surgery cannot address instability underpinned by muscle patterning deficits (as in type 3 shoulders).
The line is less clear for people that experience significant pain and disability with recurrent dislocations over time. Surgical opinion is advised in these “worn loose” shoulders especially if episodes become more frequent and require less force to dislocate.
What does surgery involve for traumatic dislocations?
Bankart lesions will typically undergo arthroscopic repair to stitch up the damaged labrum or glenoid cartilage. For larger lesions involving significant glenoid bone loss, a Latarjet procedure is used to ‘fill in’ the bony gap with bone taken from the coracoid process. Arthroscopic surgery can also be used to fill in humeral head defects (Hill Sachs lesion) using part of the posterior shoulder capsule and supraspinatus tendon.
Do I need to wear a sling?
Sling immobilisation with the arm in external rotation has traditionally been used to prevent recurrence. Recent evidence suggests that the external rotation component does not confer any benefit compared to standard sling immobilisation when it comes to recurrent instability71,72. More importantly, the risk of recurrent instability is not reduced with sling immobilisation for any greater than 7 days73. Therefore, it is advised that shoulders should be only immobilised for a short period of time and it is best to mobilise as early as comfort dictates74.
What can a physiotherapist do for me?
Your physiotherapist will provide advice and education specific to your shoulder presentation. This will encompass load modification, pain management, and an individualised exercise program to improve confidence in your shoulder and help you return to your desired activities. Factors such as direction of instability, presence of structural or muscle patterning deficits, and baseline pain and disability will inform exercise prescription. A guided exercise program combined with a solid understanding of the cause and self management strategies should yield excellent results if given sufficient time. A trial of conservative management for at least 6 months is recommended for people between the age of 25 and 40 after primary dislocation73. A systematic review by Eljabu et al (2017)68 concluded that physiotherapy confers greater functional outcomes and patient satisfaction compared to surgery. Given the fact that the risk of dislocation reduces with age, physio is highly recommended for those over the age of 30 that do not have significant structural pathology, or goals to return quickly to high level sport.
Exercise for RCRSP and shoulder instability:
As you have probably gathered, exercise therapy is a highly effective treatment for RCRSP and shoulder instability. Given that it has comparable outcomes with surgery in the majority of cases, it should be the first line management for these conditions.
The key principles undermining successful exercise rehabilitation and functional outcomes include:
- Exercise must be progressive in nature by increasing load, range of motion, stability demands and cognitive challenge.
- Exercises must be enjoyable and relate to your specific goals
- Exercises should aim to improve not just the overall capacity of the shoulder, but the entire kinetic chain.
- There should be a variety of exercises to challenge the shoulder complex in its different roles and movements. I.e. working on force/torque production and absorption, proprioception and stabilisation through different movements and varying contexts.
- Incorporate both open and closed kinetic chain exercises to prepare the shoulder for the demands of everyday life and sport.
Most people with RCRSP and shoulder instability should be able to tolerate the following exercises. Start off with slow controlled movements through tolerated range of motion. Aim to increase range of motion and increase stability demands over time.
Closed and semi-closed kinetic chain:
- 4 point kneeling variations (weight shift, 1 leg lift, 1 arm lift, bird dogsà progress to knees off ground)
- Wall push ups
- Stability ball against the wall circles/slides
- Serratus pushups
Open kinetic chain exercises:
- Rowing variations (seated cable row, standing row, bent over row, ½ kneeling high to low row, side plank row)
- Shoulder flexion and scaption to 90degrees
- Banded pullaparts
- Shoulder external rotation variations in neutral (dumbbell side-lying, side-plank isometric external rotation into flexion)
Once symptoms have settled, the patient should be progressed to greater loads, range of motion (into >90degree flexion and abduction) and work towards functional movements (lift, push, pull and carry). Add lower body movements to exercises to increase challenge- e.g. adding a squat or lunge to a row or overhead press.
Closed and semi closed kinetic chain:
- Single arm serratus push up
- 4 point kneeling (knees off ground) with shoulder taps/ arm and leg lifts
- Bear crawls (forwards, backwards, multidirectionalà progress to band around wrists)
- Crow stand
- Push ups and pullups (add load)
- Stability ball variations (stir the pot, jack-knifes)
- Tall plank on medicine ball (add side twist)
- Tall plank slides
- Pike variations (pike push up, single arm pike, box pike, pike bear crawl)
- Side plank
Open kinetic chain exercises:
- Farmer’s carry variations (overhead, bilateral, unilateral)
- ½ kneeling press with external rotation bias
- Banded shoulder external rotation in 90/90
- Banded shoulder External rotation to overhead press
- Snow angels
- Reverse fly (banded or bent over)
- Prone raise variations
- Overhead press variations (progress from barbell to dumbbell to bottoms up kettlebell using a variety of grips)
If the athlete has goals to return to shoulder intensive sports such as throwing and swimming, plyometric exercises focusing on power should slowly be introduced into their program:
- Plyometric pushups
- Push ups on unstable surface (e.g. 1 hand on medicine ball)
- Medicine ball rapid rebound passes against wall
- Drop and catch exercise
- Plank ball tosses
- Medicine ball rotational tosses
- Medicine ball bench press throw with partner
- Prowler pushes
- Battle ropes
- Olympic lifting
This is a special acknowledgment Jared Powell, renowned shoulder physiotherapist and Expert Edition guest on episode #167. Jared is changing the way clinicians approach shoulder presentations by presenting the latest research to inform clinical best practice. Click here to listen to episode #167 where Jared and Brad dive deep into all things rotator cuff related shoulder pain.
Julian Tubman (APAM)
Featured in the Top 50 Physical Therapy Blog
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