My first blog took an introspective look at how most people might define the shoulder. This blog looks at how medical professionals define the shoulder. To understand a medical definition, you will need to familiarize yourself with some medical terms used to describe shoulder parts.
Anatomy was a core subject during my first year of studying physiotherapy back in 1977. I still remember the smell of formaldehyde when I walked through the doors of the anatomy building at Queens University. Glass receptacles of various shapes and sizes were meticulously arranged throughout the building, each containing a carefully dissected and labelled body part. The “anatomy library’ was an excellent learning resource for all students of anatomy. Physiotherapy and Occupational therapy students did not perform dissection, but when our region of study warranted it, we were provided with dissected upper or lower limbs.
I knew that a dissected upper limb would be waiting for us on the first day we arrived to study the upper limb, but what appeared on the table was puzzling. The arm was there, but a mass of crumpled, shredded-looking tissue was attached to the upper end. My first thought was “What is this…half of the muscle from the back?”
So began my upper limb anatomy education. I soon discovered that the upper limb includes the shoulder blade, collar bone, muscles, joints and the connective tissue (capsules, ligaments and tendons) that hold everything together. Some of the muscles around the shoulder blade are large and do, in fact, attach to the ribs, neck and back. These additional muscles and bones are generally referred to as the 'shoulder girdle’ or the ‘shoulder complex’.
To learn basic shoulder anatomy, there are many educational tools available online. Hopkinsmedicine.org provides an excellent summary, including a short video: Shoulder Anatomy.
When watching the video, notice that there are descriptions for three joints, three bones and numerous muscles.
If human anatomy is to be the resource for our ‘shoulder’ definition, there should be some consistency for what is considered the medical definition of the shoulder.
To get a sense of how the shoulder might be defined by medical professionals, 13 online definitions were reviewed. No two were the same, but many were similar. Only TWO included a description or mention of the shoulder girdle complex, and only ONE described our shoulder girdle's connections with our torso, or ‘axial skeleton’*. The clavicle connects with the breastbone or sternum, and the scapula connects with the ribs.
*Axial skeleton – consists of the bones of the head, the ossicles of the middle ear, the hyoid bone, the rib cage, sternum, and vertebral column.
Rather than read and compare all 13 definitions, a summary of descriptive points is provided here:
1. Refers to the glenohumeral (GH) or ball and socket joint.
2. States that it (‘the shoulder”) is large, and/or freely moving, mobile, and/or subject to dislocation.
3. Describes the shoulder as being ‘complex’. (May refer to GH joint or shoulder joint complex).
4. Describes tissues at or near the GH joint. May include GH joint cartilage, capsule, labrum, the ‘tip of acromion’, GH ligaments, rotator cuff or biceps muscles (GH muscles).
5. Describes or refers to three bones – humerus, clavicle, and scapula. Ref #3,6, and 13 refer to two main bones. Refs # 6 and 8 refer to two joints: GH, acromioclavicular (AC).
6. States that the shoulder connects the arm to the torso. (Ref #5 mentions the GH joint, but no accompanying description of the remaining parts of the shoulder girdle).
7. Describes or refers to four bones: humerus, scapula, clavicle, and sternum (axial skeleton including ribs) and four joints: GH, AC, sternoclavicular (S/C) and scapulothoracic (S/T).
8. Describes shoulder girdle, or upper limb connection with the axial skeleton.
These tables compare the thirteen online definitions:
Descriptive Points | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
Ref#1 | * | * | * | | | | * | * |
2 | * | * | * | | | | * | * |
3 | * | | | * | * | | | |
4 | * | | | * | * | | | |
5 | * | * | | | | * | | |
6 | * | * | | | * | | | |
Descriptive points | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
Ref#7 | * | * | | * | * | | | |
8 | * | | | * | * | | | |
9 | (*) | | * | | * | | | |
10 | * | * | | * | * | | | |
11 | | | | | | * | | (*) |
12 | | | | | | * | *(5) | |
13 | * | | | * | * | | | |
1. physiopedia.com.
3. Rx list
7. Wikipedia
9. Tablers
13. Medicine net.com
Of these 13 ‘shoulder’ definitions, ten identify the glenohumeral or ball and socket joint as the ‘shoulder’ or the ‘shoulder joint’. Reference #9 describes the location of the glenohumeral joint: “…the region of the proximal humerus, clavicle and scapula.” Essentially, #9 can be included as a glenohumeral description.
11/13 (85%) of the definitions identified the glenohumeral joint as the shoulder or the shoulder joint.
Definitions one and two were the only ones that named and correctly described the four joints of this shoulder joint complex.
Five definitions referred to three bones in the shoulder, three indicated that there were two bones, and two references cited two joints in the shoulder. Two references cited four bones and four joints, and one cited five joints – however, I am certain that the coracoclavicular ligament is not a joint.
The shoulder (GH joint) was described as part of the shoulder girdle or shoulder joint complex in two definitions (#1, 2). Definition # 11 however did include the general area: “the laterally projecting part of the human body formed of the bones and joints with their covering tissue by which the arm is connected with the trunk” While it is often thought that the ‘shoulder’ connects with the torso (#5,11,12), the more accurate definition of arm attachment, where the SC and ST joints connect with the axial skeleton (sternum and ribs), is only mentioned in two definitions (#1,2).
This small survey was meant to be a ‘snapshot’ of medical definitions for the shoulder. It does not represent ALL sites online because the number of online medical shoulder definitions is very large. This snapshot used definitions from a physiotherapy source, a published medical paper, several medical dictionary sources as well as definitions from organizations (Arthritis society, AAOS), hospitals and clinics. If this survey was composed entirely of hospital and clinic- sponsored sites, the definitions for the shoulder be close to or the same as those for #4 and #8: GH Joint=Shoulder joint, 100% of the time.
Why do medical professionals refer to ‘the shoulder’ when they are talking about the glenohumeral joint?
The noun ‘shoulder’, when referring to a human shoulder, refers to a complex region that cannot be characterized by the description of a single joint. The reality is, we SEE a single joint, and it appears that this single joint is the source of almost all our ‘shoulder' complaints. The ‘separated’ shoulder (A/C joint) and the fractured clavicle are two examples where the source of a ‘shoulder’ problem is not related directly to the glenohumeral joint.
When communicating with the public, it is necessary to highlight information that is the most relevant. A detailed description of the entire shoulder girdle is not light reading and most people, interested only in getting better, will not have any interest in learning the complex details of the shoulder girdle. Furthermore, most shoulder problems do occur at the GH…don’t they?
The best place to begin answering this question is with some information about shoulder diagnosis.
While there is some variation from one country to the next and from one medical profession to the next, shoulder diagnosis is surprisingly consistent.
The clinical assessment is the essential first step toward the shoulder diagnosis. There are now several evidence-based* assessment tools that can assist primary care physicians and allied health professionals at the primary care level. These clinical decision-making tools can help to streamline the assessment, diagnosis, and management of most shoulder conditions.
*Evidence-based: denoting an approach to medicine, education, and other disciplines that emphasizes the practical application of the findings of the best available current research (defn. from Oxford Languages)
Two examples of evidence-based shoulder assessment and management tools are the Consensus for a primary care clinical decision-making tool for assessing, diagnosing, and managing shoulder pain in Alberta, Canada and The Diagnosis and Management of Soft Tissue Shoulder Injuries
and Related Disorders Best practice evidence-based guideline – New Zealand.
Both tools provide an assessment algorithm (flowchart).
Both tools screen out patients who might have more serious medical problems like fractures, cancer, infection or other diseases. These are called ‘red flags’.
Both tools screen out shoulder problems that are the result of another problem, outside of the shoulder. Neck, back, or neurological problems for example. These are sometimes called ‘extrinsic’ problems.
Both groups ultimately direct practitioners to one of a small number of likely shoulder diagnoses:
Alberta Group | New Zealand Group |
Rotator cuff disease | Rotator cuff disorders |
Adhesive capsulitis (frozen shoulder) | Frozen shoulder |
Biceps pathology | |
Superior labral tear (glenohumeral instabilities) | Glenohumeral instabilities |
Osteoarthritis | Acromioclavicular and Sternoclavicular joint disorders |
Guide suitable for adult men and women > 18 yrs presenting with shoulder pain resulting from acute or chronic shoulder conditions | Guideline written for adolescent and adult patients with history of trauma. Excluded patients: arthritis, arthritic conditions, chronic pain and occupational overuse disorders. |
These clinical decision-making tools were designed to improve the quality of care for most shoulder patients. Streamlining and standardization limit diagnostic choices to 5 or 6 individual problems. Most shoulder diagnoses (3/5) in the NZ group are GH, and all the diagnoses listed in the Alberta tool are related to the GH joint.
Scapulothoracic disorders are described as being ‘outside of the shoulder’ according to the NZ group. The Alberta tool suggests that the scapular position should be observed during the initial examination. The scapula is not mentioned again for the remainder of the screening tool. Scapulothoracic dysfunction is not mentioned at all.
According to these guidelines, a problem in the region of the scapula or at the ST joint will not be recognized as a possible shoulder diagnosis.
Is a scapular problem NOT a shoulder problem?
Standardized diagnostic coding guidelines (ICD-10) classify scapular conditions along with other shoulder problems. Where else would they be placed? Technically, we are still describing the upper limb.
A patient, whose 'shoulder' problem is screened out due to a possible neurological problem may be referred to a neurologist, and those with other possible medical conditions are referred appropriately.
If a patient has multiple problems in and around the shoulder (patients with a scapulothoracic (ST) problem and almost all chronic shoulder patients present this way), screening tools designed to isolate a single diagnosis become invalid. A patient with a ST problem and no identifiable pathology at THE shoulder (GH) joint is also left with no specific diagnosis, and as a result, no specific treatment plan.
Like all general screening tools, these shoulder algorithms work for MOST, but not for all.
You may have already guessed that this blog and my subsequent blogs will not provide any specific information about the GH joint or the five or six most common shoulder diagnoses as outlined in these two clinical decision-making tools. If you are looking for information about the rotator cuff, adhesive capsulitis, biceps pathology, glenohumeral instabilities, labral tears, A/C or S/C dysfunction, a Google search will overwhelm you with studies, meta-data, outcome statistics and treatment guidelines. I am in no position to offer any further information about a topic that, in my humble opinion, is already over-represented.
Many shoulder problems are complex, and as a result, they often become chronic. * Chronic problems are more likely to be diagnosed with a non-specific diagnosis. For example, Parsonage-Turner Syndrome, Chronic Pain Syndrome or Myofascial pain syndrome. The ST joint may be the underlying source of a shoulder problem, but medical professionals are reluctant to consider this option. There are many good reasons for this. We can explore these reasons and more, in my next blog…coming soon.
*Chronic – an illness or problem that lasts a long time, is recurrent, persistent or difficult to irradicate.