"Subacromial shoulder pain" is the current iteration of what has been historically termed "subacromial impingement syndrome" after Neer's 1972 paper describing bursal sided cuff tear associated with underside acromial outgrowth (at least in some of the small series). While it's true that exostosis of the outer end of the acromion can cause a mechanical irritation of the subacromial content (including the subacromial bursa and the superior aspect of the rotator cuff), this is less commonly encountered than rotator cuff dysfunction causing alterations in humeral head migration, and subsequent ossification of the coraco-acromial ligament. Put simply, in most patients, rotator cuff dysfunction causes changes in the acromion, not the other way around.
Knowledge Check
In most patients, rotator cuff dysfunction causes alterations in humeral head migration and subsequent ossification of the coraco-acromial ligament, rather than acromial changes causing cuff pathology.
Some background information is in order to help frame the subjective examination.
The association between age, activity level, and the location of partial thickness rotator cuff tears (partial thickness rotator cuff tearss) is strongly linked, as the likely pathogenesis differs significantly between younger, highly active patients (often traumatic or overuse-related) and older, less active patients (often degenerative).
1. Age and Tear Location¶
The prevalence and typical location of partial thickness rotator cuff tears correlate strongly with age.
Patient Group Pathogenesis Typical Tear Supporting Details (Age) Mechanism Location
Older Patients Intrinsic Primarily Tears in patients **over (Degenerative) factors, the articular side 35 years old are primarily of the supraspinatus overwhelmingly centered in degeneration, tendon**. the anterior half of the aging, and cuff (88% in one study). reduced This location is vascularity. consistent with traditional outlet impingement theory associated with age-related wear.
Younger Patients Extrinsic Located at PASTA lesions were found (Highly factors, the **humeral to be **significantly more Active/Trauma) specifically insertion frequent in the younger repetitive (footprint), often population (patients tensile referred to \<40 years old) compared overload or as rim-rent to the older population. internal tears or PASTA The average age of impingement, lesions (Partial patients with rim-rent are theorized Articular-Sided tears was 31 years, which to play a large Supraspinatus Tendon was statistically role. Avulsions). significantly younger than those with partial tears located more medially in the critical zone (average 40 years). The predominance of PASTA lesions in younger patients suggests a more repetitive traumatic mechanism rather than pure degeneration.
Intratendinous Degenerative **Concealed
Tears (CID) changes and Interstitial
shear forces Delamination
within the (CID)** lesions
tendon. occurred in almost
equal measure in
patients under 40 or
over 40 years of
age, suggesting they
often develop based
on degenerative
changes rather than
purely age-specific
factors.
2. Activity Level and Tear Location/Pathogenesis¶
Activity level, particularly involvement in overhead athletics or demanding work, significantly influences both the location and mechanism of the tear.
A. Overhead Athletes partial thickness rotator cuff tearss in overhead throwing athletes, such as baseball pitchers, represent a distinct pathology.
• Location: Tears in younger overhead athletes are typically articular-sided tears of the dominant arm, specifically initiating at the supraspinatus-infraspinatus interval. This location is described as being posterior to the location commonly seen in the older, non-athlete population.
• Mechanism: The tear is often attributed to mechanisms resulting from the throwing motion, including:
◦ Internal impingement caused by compression of the posterior articular surface of the rotator cuff tendons between the humeral head and glenoid rim during specific movements (abduction and external rotation).
◦ Repetitive tensile overload from the eccentric traction forces required to decelerate the arm during the throwing phase.
• Prevalence: The prevalence of full or partial thickness tears in the dominant throwing shoulder of asymptomatic elite overhead athletes was reported to be 40% in one study.
B. General Overuse and Extrinsic Factors partial thickness rotator cuff tearss stemming from extrinsic compression mechanisms often present differently than intrinsic degenerative tears.
• Work Load: Working with the shoulder above **90∘ is associated with an **increased risk of symptomatic rotator cuff tendinopathy.
• Tear Surface Link: There is a relationship between the tear surface and the likely primary mechanism:
◦ Articular-sided tears are thought to result from primarily intrinsic factors such as degeneration, decreased vascularity, and decreased tensile strength.
◦ Bursal-sided tears may have a greater association with extrinsic factors such as compression from coracoacromial arch narrowing (impingement). Cadaveric evidence supports this, showing that bursal-sided tears are always associated with attritional lesions on the coracoacromial ligament and anterior acromion, whereas articular-sided tears typically have an intact acromion undersurface.
3. Activity Level and Tear Progression Risk¶
Activity level is critical in determining the risk of progression for existing tears, particularly during rehabilitation. This risk is highly dependent on patient-specific tendon properties.
• Small Tears and ADL: Small tears (less than 1 cm in size, or 20--30% of the tendon width) appear unlikely to progress during activities of daily living (ADL), such as drinking or brushing teeth, because the resulting strain does not exceed the tendon\'s failure strain.
• Medium Tears and Strenuous Exercise: Medium-sized crescent tears (1--3 cm, or 40--50% of the tendon width) are at a higher risk of progression during more strenuous physiotherapy exercises, specifically prone abduction or external rotation at **90∘ abduction**. This risk applies to tears located in both the middle and posterior regions of the supraspinatus tendon.
Knowledge Check
Medium-sized crescent tears (1-3 cm or 40-50% of tendon width) are at higher risk of progression during strenuous physiotherapy exercises like prone abduction or external rotation at 90°, while small tears appear unlikely to progress during typical activities.
• Progression Rate: Regardless of activity, nearly half (49%) of patients undergoing non-surgical treatment experience an increase in tear size between the two- and three-year follow-up periods
Patient education¶
As exercise is a primary intervention for this disorder, and its success is completely contingent on adherence to the prescribed exercises, over weeks, patient understanding is crucial to engagement with, and completion of the exercise programme. The following is provided as text that can be modified to your needs to create patient educational material.
What is Rotator Cuff Tendinopathy?¶
Rotator Cuff (RC) Tendinopathy is a very common condition and is frequently cited as the most common cause of shoulder pain seen in primary care.
It refers to persistent pain in the shoulder tendons, coupled with a loss of function. RC tendinopathy is an umbrella term that includes conditions like RC tendinitis/tendinosis and subacromial bursitis.
The main characteristics of this condition are pain and weakness, typically felt during shoulder external rotation and elevation.
1. What Causes This Condition? (Pathogenesis)¶
Rotator cuff tendinopathy is considered multifactorial, meaning it results from a combination of different issues. Experts generally categorize the causes into three areas: Intrinsic (problems within the tendon), Extrinsic (external pressure/overuse), and Central (nervous system factors).
Intrinsic Factors (Related to Tendon Degradation): These factors involve degeneration inside the tendon itself, often when the load placed on the tendon exceeds its ability to heal.
• Age: Degenerative changes and RC tears (both partial and full thickness) become much more common as people age, starting around 40 years. Being over 50 years old is strongly associated with an increased risk of developing symptomatic RC tendinopathy.
• Biology: Systemic diseases like Diabetes are significant risk factors. Diabetes may affect the collagen structure within the tendon, making it weaker.
• Tendon Quality: The unique mechanical properties of a patient\'s tendon tissues play an important role in determining whether an existing tear might grow larger over time.
• Vascularity: Historically, a "critical zone" about 1 cm from the tendon attachment point was believed to have poor blood supply, hindering the healing process, although this idea has been challenged.
Extrinsic Factors (Related to External Compression or Overload):
• Overuse and Biomechanics: Work that requires holding the shoulder above 90° (overhead work) is associated with an increased risk. Heavy manual work and frequent, repetitive movements are also known associated factors.
• Impingement: This occurs when the RC tendons are compressed. This can happen externally (within the subacromial space, perhaps due to a particular acromion bone shape) or internally (common in athletes, involving compression between the humerus and glenoid rim during specific movements). The traditional theory that bone structure mechanically forces compression (impingement) has largely been challenged or rejected as the main cause.
Psychological and Central Factors: Factors known as "yellow flags" can greatly influence the severity and persistence of symptoms, even if the structural pathology is mild.
• Psychological factors include anxiety, psychological distress, fear of movement (kinesiophobia), and pain catastrophising.
• Central Nervous System dysfunction, involving changes in how the brain processes pain and movement, has been identified, suggesting the nervous system itself contributes to chronic symptoms.
2. What Does It Feel Like and How is it Diagnosed? (Presentation & Assessment)¶
Symptoms: Patients typically report pain located in the anterolateral shoulder area. Pain usually increases when resisting movements during activity or training. Passive range of motion is usually preserved.
Diagnosis: The diagnosis is primarily based on a thorough clinical examination, often reached by ruling out other potential causes, as structural changes visible on imaging do not always correlate well with the severity of the symptoms experienced.
• Clinical Tests: Specific physical tests are used. The Painful arc test has the highest diagnostic value to confirm RC tendinopathy, while the Hawkins-Kennedy test is most useful for ruling it out. However, clinicians should not rely solely on special tests to confirm the diagnosis.
• Imaging: Diagnostic imaging (such as MRI or Ultrasound) is generally not recommended in the initial management. If symptoms persist for more than 12 weeks despite appropriate non-surgical care, imaging may be recommended. Diagnostic ultrasound is often prioritized because it has a similar diagnostic accuracy to MRI but is typically lower in cost.
3. What Are the Treatment Options?¶
Conservative management is the initial approach generally recommended for RC tendinopathy.
A. Non-Surgical Management (First-Line Treatment)¶
1. Active Rehabilitation Exercise Program: A personalized, active rehabilitation exercise program is the initial recommended treatment to reduce pain and disability.
◦ Goal: Exercise is vital because it can induce cellular and structural changes, improve the tendon\'s ability to tolerate load, and potentially normalize central motor control (the way the nervous system controls movement).
◦ Principles: Management involves relative rest, modifying activities that cause pain, controlled reloading, and gradually increasing movement complexity.
◦ Effectiveness: All exercise programs aimed at muscle development have been found to be effective, leading to similar improvements in pain and function. Some evidence suggests that eccentric training (where the muscle lengthens under load) may offer advantages over conventional exercises.
Knowledge Check
All exercise programs aimed at muscle development have been found effective with similar improvements in pain and function, though some evidence suggests eccentric training may offer advantages over conventional exercises.
2. Education and Lifestyle: Patient-centered education about the condition, pain management, and activity modification is an essential part of care. Lifestyle factors, such as smoking, stress, and nutrition, should be addressed as they can negatively influence musculoskeletal healing.
3. Manual Therapy: Techniques like joint mobilizations and soft tissue work may be used in addition to exercise programs to help reduce short-term pain.
B. Medical Interventions (Injections)¶
Injections are generally not recommended as a first-line treatment.
• Corticosteroid Injections (CSI): These may provide significant pain reduction in the short term (up to 8 weeks) but are not recommended as the initial treatment. CSI, especially multiple injections, may increase the risk of an existing tear progressing. If used, using ultrasound guidance is preferred for subacromial injections.
• Platelet-Rich Plasma (PRP): The efficacy of PRP injections is currently unclear and the evidence is conflicting. It is not recommended as a first-line treatment. However, leukocyte-poor PRP has shown promise in improving pain and functional outcomes, particularly for Partial-Thickness Rotator Cuff Tears (PTRCTs).
• Calcific Tendinopathy: If calcium deposits are present and the condition has failed to respond to initial treatment, calcific lavage (an ultrasound-guided procedure to remove the deposits) should be used to reduce pain and disability.
C. Surgical Management¶
• Decompression Surgery: Arthroscopic subacromial decompression surgery (acromioplasty) is generally not recommended for treating RC tendinopathy. Long-term studies show that this surgery provides no additional clinical benefits compared to supervised exercise treatment alone.
• Treatment for Tears (PTRCTs): Surgery for partial-thickness rotator cuff tears is usually indicated only if non-surgical treatments fail after 3 to 6 months, or if the tear is large (greater than 50% thickness).
4. What is the Outlook? (Outcomes and Prognosis)¶
Prognosis and Persistent Symptoms: Rotator cuff tendinopathy can cause significant functional limitations. Despite treatment, up to 50% of patients experience ongoing pain and disability beyond 12 months.
Risk factors for persistent pain include being over 55 years old and perceiving high job demands.
Tear Progression (Focus on the Supraspinatus Tendon): If you have a rotator cuff tear, the risk of it getting larger depends on its size and the activities you perform:
• Small Tears (less than 1 cm, or 20--30% of the tendon width) are generally unlikely to progress during activities of daily living (like drinking or brushing teeth). They also appear unlikely to progress during typical physiotherapy exercises.
• Medium Tears (1--3 cm, or 40--50% of the tendon width) are at a higher risk of tear progression during more strenuous physiotherapy exercises, specifically those that involve lifting the arm up and away from the body (like prone abduction or external rotation at 90° abduction).
• Overall, tear size increases were reported in 49% of patients undergoing non-surgical treatment between the two- and three-year follow-up periods.
Success of Exercise: Exercise programs offer outcomes that are comparable to those achieved by surgical intervention, even for atraumatic partial- and full-thickness RC tears. This approach also provides general benefits, reduces sick leave, and minimizes costs.