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#439 Shoulder Pain: Impingement, Bursitis, Tendonitis, Cuff Tears, and Arthritis with Dr. Ted Parks

May 13, 2024 | By



Transcript available via YouTube

Repair and replace your old approach to shoulder pain! We cover shoulder anatomy, explain the continuum of impingement syndrome (from bursitis to tendonitis to rotator cuff tears to cuff tear arthropathy), how to take a good shoulder history, perform a high-yield physical exam, when to refer, and when to get an MRI. Plus, how to differentiate glenohumeral joint arthritis from frozen shoulder, and how to diagnose AC joint pathology. We’re joined by everyone’s favorite orthopedic surgeon, inventor, and renaissance man, Dr. Ted Parks.

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Show Segments

  • 00:00 Intro
  • 05:38 Shoulder Anatomy
  • 14:47 Continuum of Impingement Syndrome
  • 33:41 When to order an MRI
  • 36:28 Glenohumeral joint arthritis vs frozen shoulder
  • 51:50 AC joint arthritis 
  • 62:25 Outro

Shoulder Pain Pearls from Ted Parks

  1. In primary care, we can separate shoulder pain into three common buckets: subacromial space impingement, glenohumeral disease vs frozen shoulder, and AC joint arthritis.
  2. The purpose of the rotator cuff is to “hold the ball in the socket”. 
  3. “Impingement is…a blanket diagnosis that covers bursitis, impingement of the rotator cuff, and even the biceps tendon.”
  4. Think of subacromial space impingement as a continuum from subacromial bursitis to tendonitis to cuff tears. 
  5. Patients with either impingement syndrome or glenohumeral joint arthritis might have discomfort reaching overhead. However, patients with impingement syndrome would not be bothered by active or passive external rotation (with elbows at their side) because the subacromial space is wide open in this position.
  6. Frozen shoulder and glenohumeral arthritis have similar exam findings (restricted external rotation) but can be differentiated by shoulder X-ray (normal X-ray in frozen shoulder)

Shoulder Pain Show Notes

Shoulder Anatomy

(Parks, T. (2018). Practical Office Orthopedics. McGraw-Hill.) 

“There isn’t a single shoulder joint. There’s the glenohumeral joint between the ball and socket, the AC joint between the clavicle and the acromion, and the scapulothoracic joint (which we can forget about).” -Dr. Ted Parks

  • Relevant joints include the acromioclavicular (AC) and glenohumeral (GH) joints.
  • The glenoid fossa of the GH joint is shaped more like the surface of a golf te than a bowl to allow for an increased range of motion (especially compared to the hip).
  • The acromion forms the roof of the subacromial space overtop the subacromial bursa and the rotator cuff muscles below. 
  • The rotator cuff muscles attach around the humerus like the cuff of a shirt sleeve.
  • The rotator cuff consists of the supraspinatus, infraspinatus, subscapularis, and teres minor. Their purpose in life is to hold the ball into the socket. The first three muscles can all become impinged in the subacromial space, but we can forget the minuscule teres minor muscle because it does not have clinical relevance. 
  • The long head of the biceps tendon also passes under the acromion and can become impinged.  

Three common buckets of shoulder pain in primary care

  1. Subacromial space Impingement
  2. Glenohumeral arthritis vs frozen shoulder
  3. AC joint arthritis

Kashlak Pearl: Patients with either impingement syndrome or glenohumeral joint arthritis might have discomfort reaching overhead. However, patients with impingement syndrome should not be bothered by passive or active external rotation (with the elbows at their side) because the subacromial space is wide open in this position. AC joint disorders can be identified by inspection and palpation of the AC joint. 

Shoulder Imaging

X-rays (plain films) showing loss of space (cartilage) between the humeral head and the GH fossa can diagnose glenohumeral arthritis and differentiate it from frozen shoulder which has a normal X-ray (Parks, 2018). AC joint arthritis can also be identified with plain films.

Dr. Parks mentions that MRIs are often required by insurance companies prior to surgery for impingement syndrome and rotator cuff tears, but in his opinion, they are not necessary because most patients can be diagnosed clinically by history, exam, and response to treatment (e.g. glucocorticoid injection).

Shoulder Impingement Syndrome

Shoulder Impingement

Impingement is a blanket diagnosis covering bursitis, tendonitis, and cuff tears. Dr. Parks likes to think of it as a continuum progressing from bursitis to rotator cuff/biceps tendonitis to cuff tears to cuff tear arthropathy, with the latter being the most severe. Cuff tear arthropathy involves large, chronic tears with frayed edges, like a pair of ripped, well-worn jeans with a hole in the knee. These cuff tears are difficult to treat, too big to be repaired, and may require a reverse total shoulder arthroplasty (Parks, 2018).

Patients with impingement syndromes complain of pain with overhead reach because this position narrows the subacromial space and causes pain.

Mechanism of impingement/cuff tears

The subacromial bursa, rotator cuff muscles, and the long head of the biceps can all become impinged, irritated, and inflamed by recurrent compression/friction from the acromion (Parks, 2018). Dr. Parks notes that over time the tendons can fray, weaken, and eventually tear even with a trivial force like lifting a garbage bag. These tears are different from sports injuries in which a “normal” muscle experiences “abnormal” force and tears (i.e. the rotator cuff muscles become “abnormal” and tear from “normal” forces).

Long head of biceps tear

Chronic tendonitis of the long head of biceps can lead to fraying and rupture (called a “popeye deformity”), but this injury tends to be well-tolerated and without a need for surgery. Supination is more affected than elbow flexion, which only loses about 5% of its strength (Parks, 2018).

Physical exam in shoulder impingement

(Parks, 2018)

  • Check for pain with forward flexion above 90 degrees or abduction above 90 degrees.
  • Palpate for tenderness of the anterior shoulder when the patient places both arms behind their back. This maneuver allows palpation of the bursa, rotator cuff, and/or biceps tendon. 
  • Next, assess strength and discomfort during active, resisted external rotation (tests infraspinatus) and internal rotation (tests subscapularis).
  • Then, perform the empty can test to check for pain or weakness of supraspinatus.
  • A glucocorticoid and lidocaine injection of the affected shoulder can help differentiate weakness due to pain from true weakness due to a rotator cuff tear (expert opinion).

Treatment for impingement

“Physical therapy is pretty much the first-line treatment for anyone with shoulder impingement.” -Dr. Ted Parks

(Parks, 2018)

  • Physical therapy (Hopewell, 2021) to strengthen the infraspinatus and subscapularis muscles can provide a downward force to reduce impingement. One caveat: Dr. Parks recommends avoiding repeat overhead exercises which continue to aggravate the irritated shoulder, akin to repeatedly biting the inside of your cheek.
  • A response to glucocorticoid injection can help confirm the diagnosis of impingement and increase confidence that surgery with subacromial decompression with or without tendon repair will be effective (expert opinion).
  • Recall from #307 Hotcakes that in the GRASP trial, a single session of “best practice” physical therapy was non-inferior to multiple sessions and that glucocorticoid injection did not add significant clinical benefit, especially in the long term.
  • There may be an advantage to early surgery in acute rotator cuff tears (rare), but nonoperative treatment should be attempted before considering surgery for chronic tears (common).
  • Small, medium, and even large chronic tears can be fixed surgically along with subacromial decompression to prevent future tears.
  • Massive chronic cuff tears are treated with reverse shoulder replacement surgery.  

Glenohumeral (GH) Arthritis

“The real differentiator on physical exam (between glenohumeral arthritis and impingement syndrome) is how they behave with their elbow at their side for passive or active external rotation.” -Dr. Ted Parks

(Parks, 2018)

  • Osteoarthritis of the GH joint, aka glenohumeral arthritis, occurs when the cartilage of the ball and of the socket is worn away, leaving exposed bone.
  • Cartilage is numb (it has no innervation), but bone does have innervation, so grinding bones hurt!
  • The “high-mileage shoulder”, due to heavy use from athletics or occupation, or adults 60 or older are at risk for GH joint arthritis.
  • The shoulder wears down less quickly than the knees or hips, and GH arthritis is better tolerated because the shoulder is a non-weight-bearing joint.
  • First-line treatments are non-surgical care, including NSAIDS, physical therapy, and glucocorticoid injection.
  • Shoulder replacement is a last resort for patients who do not improve with conservative therapy. Dr. Parks notes the lifespan of a shoulder replacement is uncertain, and this must be weighed against severity of symptoms and a patient’s life expectancy.

Frozen Shoulder vs GH Arthritis

(Parks, 2018)

  • Frozen shoulder and GH arthritis are hard to differentiate on exam alone.
  • Patients with both GH arthritis and frozen shoulder have difficulty with active/passive external rotation with the affected elbow held at their side (e.g. “holding up a bank”).
  • The patient with a frozen shoulder will have a normal X-ray with a clear space representing a preserved coating of cartilage on the humeral head and acetabulum of the glenoid.

Explaining Frozen Shoulder

Dr. Parks tells patients that the layers of muscle in the shoulder are stacked on each other like the sheets on a bed and must glide over one another. If they stop moving (e.g. ICU stay) or if the space fills with blood (e.g. from trauma), then the layers can adhere to each other, and frozen shoulder can develop. Additionally, patients with diabetes are at higher risk of frozen shoulder, but we don’t know why.

Treatment of frozen shoulder is conservative management with a focus on restoring range of motion, but some patients need the adhesions broken and range of motion restored by manipulation under anesthesia (Parks, 2018).

Acromioclavicular (AC) Joint Arthritis

(Parks, 2018)

  • AC joint arthritis is a clinical diagnosis that can be supported by X-ray findings. 
  • Patients will have tenderness to palpation of the AC joint. Dr. Parks recommends palpation of both sides at the same time to compare. 
  • The cross-arm impingement test (positive “scarf sign”) can also be helpful. Ask the patient to tap their opposite shoulder “like they are patting themself on the back”
  • Treatments include NSAIDS, glucocorticoid injection, or surgery in advanced cases.
  • Surgery often involves resection of the clavicular head.


Parks, T. (2018). Practical Office Orthopedics. McGraw-Hill.


Listeners will develop a standard approach for shoulder pain diagnosis and management 

Learning objectives

After listening to this episode, listeners will…

  1. Develop a differential diagnosis for shoulder pain
  2. Perform a high yield shoulder exam
  3. Diagnose and treat common causes of shoulder pain


Dr. Ted Parks is the author of Practical Office Orthopedics (McGraw Hill). The Curbsiders report no relevant financial disclosures. 


Watto MF, Parks T, Garbitell B, Witt L,Williams PN. “#439 Shoulder Pain: Impingement, Bursitis, Tendonitis, Cuff Tears, and Arthritis with Dr. Ted Parks”. The Curbsiders Internal Medicine Podcast. Final publishing date May 13, 2024.

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Episode Credits

Written and Produced by: Matthew Watto MD, FACP

Show Notes: Matthew Watto MD, FACP

Cover Art and Infographic: Beth Garbitelli MD

Hosts: Matthew Watto MD, FACP; Paul Williams MD, FACP   

Reviewer: Leah Witt MD

Showrunners: Matthew Watto MD, FACP; Paul Williams MD, FACP

Technical Production: PodPaste

Guest: Ted Parks MD

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