General Discussion: General Approach to Shoulder Pain

The initial focus when evaluating this patient should attempt to differentiate local shoulder pathologies versus referred/radiating pain from cervical spine pathologies, although coexisting lesions are possible and common. The areas on which to focus in this patient’s history involve recognizing significant cervical spine symptoms and focal neurologic deficits, including motor and sensory deficit of upper extremities (UE). The mode of onset, the exact location of the pain, aggravating, and relieving factors would be important in establishing a differential diagnosis ( Table 3.1 ). For example, the pain from cervical spine pathologies can be reproducible with cervical spine motion (or movement) rather than shoulder movement. Acute and abrupt onset may suggest trauma or vascular event as the underlying etiology. Rapid development of pain may suggest an inflammatory or infectious process as the underlying etiology.

The presence of sensory or motor deficits in the UEs may implicate neuropathy (cervical root, brachial plexus, mononeuropathy) as the cause of her shoulder pain ( Table 3.2 ). True muscle weakness from neural origin should be differentiated from the weakness caused by musculoskeletal pain or impaired range of motion (ROM).

Physical examination should be geared toward the differential diagnosis based on history taking, including the musculoskeletal examination of cervical and shoulder pathologies and neurologic examination to differentiate neuropathic versus musculoskeletal processes.

Common Differential Diagnoses for Shoulder Pain

• 1.
  

  Subacromial impingement syndrome —process involves impingement of structures in the subacromial region between the acromion (coracoacromial arch) and humeral head/neck (particularly, greater tuberosity). The subacromial subdeltoid bursa and supra/infraspinatus tendon are commonly impinged, causing bursitis and tendinopathy and subsequently tear ( Fig. 3.1 ).

  
  
  
  
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    The pain is located on the anterolateral aspect of the shoulder, beneath the acromion, down to the deltoid tuberosity, typically aggravated by positions or activities to narrow down the subacromial space, such as overhead activities requiring abduction and internal rotation of the humerus (engaging the greater tuberosity under the coracoacromial arch). Although this is the descriptive diagnosis to explain the mechanism, it is frequently used interchangeably with rotator cuff tendinopathy (or syndrome) or subacromial bursitis.

  
  

  
  

  
  

  

  
  

  
  

  A sagittal view of the glenohumeral joint showing the glenohumeral ligament, glenoid labrum, and biceps tendon. Sup ., Superior.

  
  

  From T.S. Mologne, Shoulder Anatomy and Biomechanics. Delee, Drez, & Miller’s Orthopaedic Sports Medicine: Principles and Practice, Elsevier, Philadelphia, 2020, 399–401.

  
  
  
  
• 2.
  

  Other shoulder impingement syndromes —although subacromial impingement syndrome is the most common, there are other shoulder impingement syndromes, including internal impingement syndrome, subcoracoid impingement syndrome, and so on. These conditions were less well known than subacromial impingement syndrome but illustrate distinctive mechanisms with different presentations. Subcoracoid impingement syndrome is the impingement of subscapularis tendon or subcoracoid/subdeltoid bursa between the lesser tuberosity of humerus and coracoid process. The pain is located in the anterior aspect of the shoulder (rather than anterolateral aspect in subacromial impingement) and provocation maneuver/activity is slightly different with adduction added to flexion and internal rotation of the humerus. Internal impingement is a less well-known cause of posterior shoulder pain. However, it is a relatively common cause of shoulder pain in a specific population (e.g., throwing athletes, such as pitcher, tennis player). The posterior part of supraspinatus and infraspinatus tendon is impinged between the humeral head and glenoid labrum during shoulder abduction and external rotation (late cocking phase in pitching).

  
  
• 3.
  

  Strains and sprain —if there is a preceding injury or trauma (such as fall, pull, etc.) to the development of shoulder pain, muscle/tendon strains or ligament sprains can be suspected. Rotator cuff strain is one of the most common diagnoses in the shoulder. Deltoid muscle strain is underrecognized but can also cause similar pain as rotator cuff strains. A subdeltoid bursa is located between the rotator cuff tendon and deltoid muscle. As a result, an accompanying bursitis is not uncommon. Acromioclavicular (AC) joint ligament complex sprain is a well-known cause of pain after trauma. Depending on the degree of ligament involvement (coracoclavicular or coracoacromial ligament) and displacement of the clavicle, a grading system (I‒VI) exists for AC sprain. Other ligament injuries (glenohumeral [GH] ligaments and coracohumeral ligaments) are underrecognized and not easily detected without advanced imaging. An untreated injury can lead to painful instability later. Other structures commonly injured include the labrum of the glenoid. Depending on the injury pattern, it can cause painful clicking and occasionally mechanical locking. Superior aspect of the labrum (superior labrum anterior and posterior) is a common site for the labral tear, and the presentation can be similar to an AC joint sprain. As degenerative labral pathology is very common, the correlation of the event/injury and the imaging finding is important.

  
  
• 4.
  

  Osteoarthritis —common locations of osteoarthritis in the shoulder include the AC joint, GH joint, and sternoclavicular (SC) joint. Depending on the location of the joint, the pain can be superior at the AC joint and anteromedial/medial at the SC joint and deep/vague/diffuse in the GH joint osteoarthritis. The pain is gradual in onset, without preceding event or trauma, and worse with activity. Although the disease process is gradual, the patient may feel a relative abrupt onset in the case of flare-up. ROM limitation is more prominent in external rotation than internal rotation (with abduction) as in impingement syndrome. Although ROM restriction varies with the severity of osteoarthritis, it is not as severe as in adhesive capsulitis. Stiffness is present with gradual improvement with movement.

  
  
• 5.
  

  Adhesive capsulitis —the pain is gradual in onset, poorly localized, initially with overhead activity, or at night, then becomes constant. It is accompanied by painful stiffness then the pain eventually improves gradually. It is more common in females than males, peaks at 40 to 50 years old, and typically presents on the nondominant side. Adhesive capsulitis occurs in up to 20% of patients with diabetes and is more common in patients with thyroid dysfunction, Dupuytren contracture, autoimmune disease, and stroke survivors. Up to 20% to 30% of patients will later develop the symptoms on the unaffected side. Loss of ROM greater than 30 degrees on two planes (frontal, sagittal, or axial) is a commonly used physical examination criterion for diagnosis. Early loss of external rotation is also common. The diagnosis usually requires imaging studies to rule out other mimicking conditions, such as GH osteoarthritis or other inflammatory arthropathies.

  
  
• 6.
  

  Connective tissue disease— multiple joint arthralgias, fever, weight loss, fatigue, and other systemic symptoms are seen. Rheumatoid arthritis (RA) affects about 1% of adults, with shoulder joint involvement in 65% to 90% of patients with RA. It increases with advanced disease in the hand/wrist and positive rheumatoid factor. Although effusion is common, it can be subtle and can accompany constitutional symptoms. Extraarticular manifestations such as ocular, pulmonary, and cardiac manifestations are not uncommon.

  
  
• 7.
  

  Polymyalgia rheumatica —occurs in the older population, average age at diagnosis is over 70 years old, typically presents with subacute or chronic bilateral shoulder pain, significant morning stiffness (≥30 min), and can be aggravated by overhead activity because of subacromial bursitis (frequently coexisting). Bilateral pelvic girdle pain is less common than shoulder pain but occurs in about 50% of patients with polymyalgia rheumatica. It is often self-limiting over months to years. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are significantly elevated.

  
  
• 8.
  

  Idiopathic brachial plexopathy (Parsonage-Turner syndrome) —rare, but underrecognized disease, with an incidence of 1 to 4/10 ⁵ per year. It is slightly more common in males than females with a peak incidence between the second and third decades. It presents with severe shoulder pain, frequently 7/10 or higher on a numeric rating scale lasting days or weeks. Typically, the improvement of the pain is followed by weakness and atrophy of the muscle. It is a common cause of scapular winging with involvement of the long thoracic nerve and serratus anterior weakness.

  
  
• 9.
  

  Cervical radiculopathy —in C5, C6 radiculopathy, the neck pain can radiate down to the shoulder. Typically, the intensity of neck pain is more than or similar to the shoulder pain;however, significant shoulder pain without neck pain is possible. If the pain is reproduced by the cervical spine movement, particularly the Spurling maneuver (cervical extension and lateral flexion), which narrows down the neural foramen, the suspicion for cervical radiculopathy can be higher. It is often difficult to differentiate from cervical facet arthropathy because the referred pain overlaps with radiating pain. The presence of sensory (especially negative symptom/sign) or motor deficits can favor cervical radiculopathy.

  
  
• 10.
  

  Cervical facet arthropathy —cervical facet arthropathy based on imaging study is prevalent in older adults and increases with age. It is often asymptomatic, and symptomatic arthropathy typically causes pain in the midline neck with/without referred pain. C4‒C5 level is the most common level of degenerative changes, and C5‒C6 is known to be the most common location of pain with referred pain to upper trapezius and shoulder. ^, The pain can be aggravated by cervical spine extension, which is not specific. Reproduction or significant relief of pain with imaging-guided injection is required to confirm facet joint as pain generator. ^, Unlike cervical radiculopathy, it lacks focal neurologic deficits.

  
  
• 11.
  

  Myofascial pain syndrome —arguably the most common cause of the shoulder girdle pain. A patient usually complains of shoulder girdle pain with or without referred pain. Sensory abnormalities, such as tingling paresthesia, can be present. Depending on the involved muscle, pain can be referred to the occiput (trapezius), upper arm, and rarely to the distal upper extremity. The patient does not have a preceding injury or trauma but often complains of increased stress or workload. Headaches may present if suboccipital and trapezius muscles are involved. Referred pain may be felt in upper arms, elbows, and forearms with palpation of the associated trigger points. Physical examination is usually negative other than trigger point palpation with reproduction of symptoms. Skilled palpation techniques may help to identify the areas of trigger points. Abnormal postures and biomechanics are often associated with the development of myofascial pain syndrome, therefore it is important to identify and address it.

  
  
• 12.
  

  Fracture —history of trauma usually precedes. Examination reveals pain and focal tenderness with limited ROM because of pain. In patients with risk factors, only minor trauma is required to cause fracture. Subtle nondisplaced fractures can be missed without increased suspicion in elderly patients with osteoporosis. Proximal humeral fracture is particularly common in the elderly after a fall. In contrast, youth throwing athletes can develop an injury at the proximal humeral epiphysis called little leaguer shoulder. It can cause disabling pain in the shoulder, especially during throwing motion, and tenderness on the lateral aspect of the proximal humerus is common.

  
  
• 13.
  

  Septic arthritis —the shoulder is an uncommon location for septic arthritis, 3% to 5% of all septic arthritis, therefore it is underrecognized. It is more common in patients with RA, prosthetic joint, and other risk factors, such as human immunodeficiency virus (HIV). Pain can be exquisite, constant with limited ROM, accompanied by swelling, warmth, and erythema. Because of the lack of typical symptoms and signs initially, delay of diagnosis is common, either by the patient or by healthcare providers. Constitutional symptoms, such as malaise, and low-grade fever may be present. The complete blood count may be normal or show leukocytosis with left shift, but CRP and ESR are frequently elevated.

  
  
• 14.
  

  Charcot neuroarthropathy ^, —rare cause of destructive arthropathy typically related to the syrinx of the spinal cord. Diabetes mellitus is the most common underlying cause of Charcot neuroarthropathy, but more commonly involving the distal lower extremity, such as the foot and ankle. Because of a lack of pain, the patient does not recognize progressive destruction of the humeral head and glenoid until it has progressed significantly. When symptomatic, it presents with shoulder pain with decreased ROM and often with swelling and joint deformity.

  
  
• 15.
  

  Tumor and bony metastasis— the shoulder region is the third most common site for bone and soft tissue tumors. Primary bony tumors of the shoulder are more likely to be malignant with osteosarcoma and chondrosarcoma, with Ewing sarcoma being the most common. Pain from bony and soft tissue tumors is constant when present, and worse in resting position. Systemic manifestations such as weight loss may accompany.

Case Discussion

Our patient presented with indolent development of symptoms over a few months, suggesting chronicity. An acute traumatic or vascular event is less likely to be the underlying etiology of the patient’s presentation. Lack of focal sensory or motor deficit, worsening of pain with shoulder movement (especially overhead activity), and lack of focal neurologic deficit suggests local musculoskeletal pathologies as underlying etiologies.

Recognition of the pain with a specific position can be important information to further localize the lesion. For example, if the pain is reproduced by internal rotation and abduction engaging the supraspinatus or subdeltoid bursa between greater tuberosity and coracoacromial arch, subacromial impingement syndrome should be suspected. If the ROM is limited with pain in multiple directions (planes) of shoulder ROM, capsular or GH joint pathologies, such as adhesive capsulitis or GH arthropathy should be suspected. The characteristics of pain can also be useful information. Persistent pain, even on resting or night pain, may be suggestive of an inflammatory etiology (bursitis and capsulitis) rather than mechanical (tendinopathy by impingement, labral pathology). Lack of symptoms in the contralateral shoulder and other joints are against systemic disease, such as inflammatory arthropathy (RA, polymyalgia rheumatica, etc.). Absence of red flags argues against an infectious underlying etiology or tumors as the underlying cause of pain; however, laboratory tests such as ESR and CRP can be useful if there is any suspicion for an infectious or inflammatory process.

Underlying diabetes mellitus and involvement of the nondominant side with decreased ROM in multiple planes increases the likelihood of adhesive capsulitis as the diagnosis; however, other diagnoses such as GH joint arthropathy or infectious arthropathy should also be ruled out. Other bony or joint pathologies such as avascular necrosis or bony tumor are less likely, and imaging study can be helpful to rule out these conditions.

Objective Data

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