It can be a real challenge figuring out the stiff shoulder. 

Frozen shoulder is a good example. It can be overdiagnosed. Underdiagnosed. Misdiagnosed. One study by Russell et al.2 found that among primary care referrals an accurate diagnosis for frozen shoulder was 17%. They recorded all primary care referrals of frozen shoulder to a physiotherapy department during a 12-month period. Of these referrals, 17% met the inclusion criteria for primary idiopathic frozen shoulder. That is poor accuracy.

Coming up with an accurate diagnosis is crucial. To do this we need to rule out all the other causes of a stiff shoulder.

Differential Diagnosis

Understanding and ruling out the differential diagnoses for a stiff shoulder is key to getting our patients the appropriate care. There are stories of a patient taken to the operating room and having their shoulder manipulation under anaesthesia for a presumed frozen shoulder when, in fact, it was arthritis. Ouch. That’s not good. 

Diff Dx: Arthritis

Glenohumeral joint arthritis is by far the most common differential diagnosis. It can be primary osteoarthritis or secondary arthritis from trauma, fracture, dislocation, inflammatory/crystalline or rotator cuff arthropathy.3

The onset of stiffness is progressive over many years and will cause significant functional deficit, typically in patients over 60 years of age, where 32% of patients have been reported to have shoulder arthritis.4

These patients will typically report pain, ‘cracking’ and catching sensations with arm movements. They’ll also report a deep ache deep in the shoulder or in the back of the shoulder. They’ll tell you that it’s been going on for years. It’s waxed and waned. But looking at the overall trajectory it has progressively worsened over years.

It’s common for these patients to have pain with the biceps tendon. It’s the victim, not the culprit. It’s associated with the arthritic joint and can get irritated very easily in a patient with glenohumeral joint arthritis.

On physical exam you’ll feel crepitus with rotation and circumduction and a bony hard end feel. 

The clincher is arthritis on radiographs. 

Post traumatic arthropathy, from fracture or dislocation, can also lead to a global reduction in range of motion, especially severe loss of passive external rotation in the affected shoulder with arm by the side.14

Normal and advanced glenohumeral joint arthritis on x-ray.

Diff Dx: Rotator Cuff

One of the most common conditions that produces shoulder stiffness and mimics a frozen shoulder is rotator cuff pathology. This can be from impingement and bursitis or calcific tendinopathy.6 These conditions can be very painful and the patient can lose some of their range of motion. 

Rotator cuff patients will say that the pain started when they lifted a heavy object or performed repetitive overhead movements. On the other hand, frozen shoulder patients usually describe spontaneous onset without an apparent cause or a history of overactivity. 

The physical exam can also mimic frozen shoulder with painful and limited passive abduction, particularly with the arm in a neutral position or slight internal rotation. 

It’s important to correct the arm rotation with passive abduction testing. Passively abduct the arm in scapution with some external rotation. This will help the greater tuberosity of the humerus and rotator cuff clear the acromion and avoid impingement symptoms.

An acute traumatic event can also cause a rotator cuff tear (partial or complete). These patients can present with reduced range of motion and pain that mimics a frozen shoulder or they might actually develop a secondary frozen shoulder.8 Their story is key to differentiate rotator cuff pathology from a frozen shoulder. 

A cuff tear may be sore at the time but with time it usually settles (at least partially). However, if a secondary frozen shoulder develops, then pain may return. These patients may not separate from the first pain, in time or character.8  It’s important to examine the cuff for true weakness (not pain inhibition). 

Diff Dx: Posterior Dislocation

Mechanism is the most important factor in determining if a patient has a posterior shoulder dislocation. Typically the humeral head is dislocated posteriorly with the arm internally rotated and adducted.9,10,11 In adults, convulsive disorders are the most common cause. Electrocution is a classic but uncommon cause of posterior shoulder dislocation. In both situations, bilateral dislocations are not infrequent.9,10,11

Occasionally, they can be the result of strength imbalance within the rotator cuff muscles. Posterior dislocations may even go unnoticed, especially in elderly patients.9,11

We’ll typically see posterior dislocations in various sports sports such as falls from rugby, football and bikes onto a flexed internally rotated arm.12

These patients will get a reverse hill sachs lesion, an impaction fracture on the anteromedial aspect of the humeral head, on x-ray, wedge which gets locked into the glenoid corner. They’ll also get a reverse bankart lesion, a posterior labral tear. 

These patients will classically present with a block to external rotation. They’ll have reasonable flexion but block to external rotation. A lot of time they can’t even get to neutral, stuck in internal rotation.

These patients can be easily diagnosed with frozen shoulder when in fact it was a posterior dislocation. That’s why every patient always needs two x-ray views, axillary and true AP view, which are perpendicular to one another, to adequately diagnose a posterior dislocation.9,11,12 

(1) Posterior labral tear in magnetic resonance arthrography12 and (2) reverse hill sachs lesion.13

Diff Dx: Avascular Necrosis

Avascular necrosis (AVN), also known as osteonecrosis of the humeral head, is a known complication of the proximal humeral.15 AVN of the humeral head can cause significant decreased range of motion at the glenohumeral joint including passive external rotation and abduction.

A pneumonic for the most common causes of avascular necrosis is ‘STARS’ - steroid, trauma, alcohol, radiation, sickle cell.

Another pneumonic is ‘Plastic Rags’ - pancreatitis, pregnancy,  lupus (SLE), alcohol excess (chronic), steroids, trauma, idiopathic, infection, caisson disease, collagen vascular disease, radiation, rheumatoid arthritis, amyloid arthropathy, Gaucher disease, sickle cell disease.

This is where x-rays are important for an accurate diagnosis. 

Post traumatic arthropathy can lead to a global reduction in range of motion, especially severe loss of passive external rotation in the affected shoulder with arm by the side.14

Avascular necrosis due to disruption of humeral head blood supply.16

Diff Dx: Malignancy

One of the worst feelings is missing a diagnosis. The only thing worse is a misdiagnosis of frozen shoulder when someone has cancer. Unfortunately, this does happen and it’s been reported in the literature after prolonged, ineffective treatment for frozen shoulder.7

A patient not getting better, but actually getting worse over a period of time, is one of the cardinal concerns that something is not right. This highlights the importance of reviewing imaging carefully with each of our patients.

Some of the other common red flag symptoms to look out for include chronic fatigue, unintended weight loss, night pain not relieved with medicine and a past history of cancer.

Some of the most common cancers mistaken for a shoulder condition, like adhesive capsulitis, are lung, prostate, kidney, thyroid, breast cancers.7

Diff Dx: Muscle Stiffness & Pain Inhibition

“Frozen in Fear” is another type of frozen shoulder.

Chronic pain can lead to muscle guarding and pain inhibition which can mimic adhesive capsulitis. It can be easy to get tricked into thinking these patients have a true frozen shoulder - it happens to everyone including shoulder specialists.

To err is human.

Pain for a prolonged period of time, say beyond 6 months, can significantly affect pain beliefs and will impact how they move. This chronic pain influences cortical change in the brain.17 The pain makes it more difficult to move and propagates a pain inhibition negative feedback loop.18

Patients with negative psychosocial factors - negative pain beliefs, fear avoidance, worrying and anxiety - impact how they move.19,20 

If you’ve ruled out the other sinister differential diagnoses; How willing is the patient to move on their own?

Some of the simple ways we can test to see if muscular in origin or the static structures like ligaments and capsule is to add compression to ‘wake up’ the glenohumeral joint and surrounding muscles. Add an isometric contraction during movement to see if range of motion improves.  A simple way of doing it is to have a patient perform an isometric contraction on an exercise ball during movement. 

You can also use the kinetic chain to initiate movement such as using the lower extremity in conjunction with the upper extremity to get movement in the shoulders. You can also work both arms at the same time and perform the movements with a tight fist squeeze. These are all little tricks to help differentiate muscle stiffness and pain inhibition from adhesive capsulitis.

References

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2. Russell S, Jariwala A, Conlon R, Selfe J, Richards J, Walton M. A blinded, randomized, controlled trial assessing conservative management strategies for frozen shoulder. J Shoulder Elbow Surg. 2014;23(4):500-507. doi:10.1016/j.jse.2013.12.026
3. Ansok CB, Muh SJ. Optimal management of glenohumeral osteoarthritis. Orthop Res Rev. 2018;10:9-18. Published 2018 Feb 23. doi:10.2147/ORR.S134732
4. Chillemi C, Franceschini V. Shoulder osteoarthritis. Arthritis. 2013;2013:370231. doi:10.1155/2013/370231
5. Lord SM, Barnsley L, Wallis BJ, Bogduk N. Chronic cervical zygapophysial joint pain after whiplash. A placebo-controlled prevalence study. Spine (Phila Pa 1976). 1996;21(15):1737-1745. doi:10.1097/00007632-199608010-00005
6. Mezian K, Coffey R, Chang KV. Frozen Shoulder. In: StatPearls. Treasure Island (FL): StatPearls Publishing; September 3, 2020.
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8. Armstrong A. Diagnosis and clinical assessment of a stiff shoulder. Shoulder Elbow. 2015;7(2):128-134. doi:10.1177/1758573215569340
9. Doehrmann R, Frush TJ. Posterior Shoulder Instability. In: StatPearls. Treasure Island (FL): StatPearls Publishing; June 22, 2020.
10. Bäcker HC, Galle SE, Maniglio M, Rosenwasser MP. Biomechanics of posterior shoulder instability - current knowledge and literature review. World J Orthop. 2018;9(11):245-254. Published 2018 Nov 18. doi:10.5312/wjo.v9.i11.245
11. Magnuson JA, Wolf BR, Cronin KJ, et al. Surgical Outcomes In The Frequency, Etiology, Direction, Severity (feds) Classification System For Shoulder Instability. Orthop J Sports Med. 2020;8(3 suppl2):2325967120S00120. Published 2020 Mar 30. doi:10.1177/2325967120S00120
12. Dhir J, Willis M, Watson L, Somerville L, Sadi J. Evidence-Based Review of Clinical Diagnostic Tests and Predictive Clinical Tests That Evaluate Response to Conservative Rehabilitation for Posterior Glenohumeral Instability: A Systematic Review. Sports Health. 2018;10(2):141-145. doi:10.1177/1941738117752306
13. Moratalla MB, Gabarda RFPosterior shoulder dislocation with reverse Hill–Sachs deformityEmergency Medicine Journal 2009;26:608.
14. Thomas M, Bidwai A, Rangan A, et al. Glenohumeral osteoarthritis. Shoulder Elbow. 2016;8(3):203-214. doi:10.1177/1758573216644183
15. Schoch BS, Barlow JD, Schleck C, Cofield RH, Sperling JW. Shoulder arthroplasty for post-traumatic osteonecrosis of the humeral head. J Shoulder Elbow Surg. 2016;25(3):406-412. doi:10.1016/j.jse.2015.08.041
16. Sugano N. (2014) Osteonecrosis of the Humeral Head. In: Koo KH., Mont M., Jones L. (eds) Osteonecrosis. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-35767-1_54
17. Yang S, Chang MC. Chronic Pain: Structural and Functional Changes in Brain Structures and Associated Negative Affective States. Int J Mol Sci. 2019;20(13):3130. Published 2019 Jun 26. doi:10.3390/ijms20133130
18. Smith BE, Hendrick P, Bateman M, et al. Musculoskeletal pain and exercise-challenging existing paradigms and introducing new. Br J Sports Med. 2019;53(14):907-912. doi:10.1136/bjsports-2017-098983
19. De Baets L, Matheve T, Traxler J, Vlaeyen J, Timmermans A. Pain-related beliefs are associated with arm function in persons with frozen shoulder. Shoulder Elbow. 2020;12(6):432-440. doi:10.1177/1758573220921561
20. Toprak M, Erden M. Sleep quality, pain, anxiety, depression and quality of life in patients with frozen shoulder1. J Back Musculoskelet Rehabil. 2019;32(2):287-291. doi:10.3233/BMR-171010