Shoulder Biomech

Question 1

Joint Stabilization

Answer 1

shoulder joint capsule is relatively lax and must rely on muscles for active stabilization.

Question 2

How does the shoulder maintain PASSIVE stability?

Answer 2

When the arm hangs freely to the side (at neutral) there is little or no active contraction of the deltoid or rotator cuff muscles b/c:

a. ) The way the articulating joint surfaces are situated – glenoid cavity is facing lateral, forward, and superior creating a lip for the humeral head.
b. ) The superior joint capsule and the coracohumeral ligament hold the humerus in the glenoid fossa against gravity. This is achieved b/c the superior joint capsule and coracohumeral ligament are usually taut creating an opposing force to the vertical weight of the humerus. This causes the pull the head of the humerus in against the upward facing glenoid cavity

Question 3

How does the shoulder maintain ACTIVE stability?

Answer 3

When the shoulder is raised in any plane away from the side of the body, the superior joint capsule becomes lax. Therefore it is the responsibility of the dynamic ligaments – the rotator cuff muscles - to maintain congruency and stabilization

Question 4

What two conditions cause abnormal alterations and compromises to shoulder stability?

Answer 4

1. ) Thoracic kyphosis- this situates the scapula in a downward rotation. This takes away the stabilizing ‘lip’ of the glenoid fossa and places the humerus into a pseudo-abduction in reference to the newly positioned scapula. In addition, the normally taut superior joint capsule and coracoacromial ligaments become lax. Therefore, the dynamic ligments (rotator cuff) take over with ACTIVE stabilization. This may lead to impingement syndrome because of the constant, increased tone in the rotator cuff group.
2. ) The same occurs in a patient with muscle paresis. Weakness or imbalance may cause the scapular muscles to orient the scapula in the same forward rotation as thoracic kyphosis. Depending on the severity of the muscle paresis, inferior dislocation or subluxation may occur if the rotator cuff muscles are affected.

Question 5

What influence does the GH joint capsule have on the shoulder during movement?

Answer 5

The fibres of the GH joint capsule face anteriorly and medially. As the arm abducts this twist in the joint capsule increases and pulls the head of the humerus into the glenoid cavity.
This increasing tension furthers abduction because the medial fibres become taught. This causes the capsule to pull the humerus into external rotation – untwisting of the joint capsule.
This also allows for further abduction b/c the external rotation also helps to prevent the greater tubercle from colliding with the acromial arch.

Question 6

What is the force couple relationship between the deltoid and the rotator cuff muscles during elevation?

Answer 6

The strong multi-pennate fibres of the deltoid act below the centre of rotation causing an upward and outward force on the humerus – this is for movement and elevation.
The rotator cuff muscles act above the centre of rotation causing an inward, downward force on the humerus – this is to help maintain the congruency of the humeral head in the glenoid cavity. These muscles oppose each other & create a force coupling necessary for shoulder elevation.

Question 7

What are other force couple relationships in the shoulder?

Answer 7

1. The three parts of the trapezius muscle and serratus anterior share a force coupling relationship to help with the rotation of the scapula. With the upward rotation of the glenoid fossa, the scapula needs to track superiorly, anteriorly and laterally.
2. The long head of the biceps helps to depress the head of the humerus with abduction of the arm in external rotation b/c of the pulley system it creates in the bicipital groove.

Question 8

What occurs with the FIRST 15-30˚ of shoulder movement?

Answer 8

During the first 15-30˚ of abduction, most movement occurs at the GH joint.
During this phase the scapular muscles stabilize the scapula against the thoracic wall

Question 9

What occurs after 15-30˚ of shoulder movement?

Answer 9

At this point the scapula begins to contribute to shoulder abduction by rotating superiorly, elevating and moving forward on the chest wall.
Scapular rotation puts tension on the conoid ligament and causes a posterior rotation of the clav (after 90* of ABD), allowing the SC and AC joints to contribute to shoulder abduction.

Question 10

What is the Scapulohumeral rhythm of the shoulder complex?

Answer 10

During 180˚ of abduction, there is a 2:1 ratio of movement of the humerus to the scapula.
Phase 1- first 30˚ is performed by the GH, 0-5˚ clavicular elevation, scapula is stabilized against the thorax and has minimal or no movement. The scapula does not move; therefore, there is no ratio.
Phase 2 – next 60˚ of elevation the scapula begins to rotate (20˚) and there is a 2:1 scapulohumeral rhythm. The clavicle continues to elevate (15˚)
Phase 3 – last 90˚ of elevation there continues to be a 2:1 ratio of scapulohumeral movement. In this final stage the clavicle rotates posteriorly (b/c of the pull on the conoid ligament) and the humerus laterally rotates 90˚ to clear the acromial arch.

Question 11

What are the osseous structures involved to achieve full arm elevation and what movements must they perform?

Answer 11

Movement of the shoulder girdle isn’t limited to only the GH, AC, SC joints and the scapulothoracic mechanism. In fact, these combined joints contribute about 160˚ to the full ROM of abduction. The remaining movement (approx. 20˚) come from other osseous components.
Upper T/S – EXT; SB and Rotation (Ipsilateral)
Ribs – 1st and 2nd bodies – descend and move posteriorly
Manubrium – SB and Rotate (Ipsilateral)
Lower T/S – SB (contralateral)
The above is for unilateral abduction. Bilateral abduction causes extension. Fixed spinal deformities cannot perform full elevation.

Question 12

History

Location:* WHERE?

Answer 12

– ant brachial pain may indicate bicipital tendonitis or Adhesive Capsulitis
– Lat brachial pain may indicate SupraSpin Tendonitis or bursitis
– Sup/lat pain may indicate an AC sprain
– L/R/B?

Question 13

History

Mechanism of Injury:* HOW?

Answer 13

– RSI: bicipital tendonitis, supraspin tendonitis
– Trauma: bursitis, AC sprain, dislocation, fracture
– Insidious: Adhesive Capsulitis

Question 14

History

Nature

Answer 14

Intermittent or Constant?

Question 15

History

Onset:* WHEN?

Answer 15

Acute, Subacute, or Chronic

Question 16

History

Pain

Answer 16

Frequency (How often does it flare-up? IF applicable)
Intensity (0-10)
Duration (How long does it last? IF applicable)

Question 17

History

Quality:* WHAT does it feel like?

Answer 17

– Muscle………….Tight, cramping, dull, achy
– Ligs/Jnt caps……Dull, achy
– Nerve……………Sharp, shooting, numb, tingling

Question 18

History

Referral/Radiating

Answer 18

Does it travel? If so, ID the specific pattern and quality of travelling pain.

Question 19

History

Systemic

Answer 19

Any underlying conditions that may present w shoulder pain: gallbladder, diaphragm, etc

Question 20

History

Timing

Answer 20

What time of day/week/month is pain at worst? What aggravates/relieves the pain?

Question 21

History

Underlying

Answer 21

Occupation, hobbies, ADLs, age/gender, sleep position, pillowing etc

Question 22

Some specific Questions:

Answer 22

 Can the patient lie on the affect shoulder at night?
 Is it difficult to perform ADLs: brushing hair, pulling off shirt, fastening bra?
 Is it difficult to perform and activities that require reaching above shoulder level?

Question 23

Observation

Answer 23

I.) Holding pattern? Posture of the arm and shoulder girdle – is the guest protecting the affected side, does the patient hold the arm close to the side or across the chest, does the Pt support the arm manually or with a sling?
II.) Functionality – ability to undress, willingness to use the arm.
III.) Anterior view
– Head and neck in midline, in relation to the shoulders
– Bilateral shoulder height: when normal, the dominant side is usually lower due to repetitive stretch to the ligaments and capsule
– Muscle size and tone: dominant side larger due to repeated use.
– Step deformity at the distal end of clavicle: indicative of a separation.
– Sulcus sign: a ‘sagging’/’flattening’ below the acromion process where a rounded deltoid muscle would be; indicative of a dislocation or deltoid paralysis
– Mal-alignment of clavicle: fractures
IV.) Posterior view
- Roundedness of the shoulders – the scapula should be equidistant from the spine.
- Scapular ‘winging’ – when the medial border moves away from the posterior chest wall.
a.) Is it dynamic? This is indicative of serratus anterior injury or a compromised long thoracic nerve, possible muscle imbalance or strain to the rhomboids or upper trapezius
b.) Is it static? This is indicative of structural deformity of the scapula, clavicle, spine, or ribs
- Scapular ‘tilting’ – this is when the superior or inferior angles tilt away from the chest wall. This is also indicative of weakness and instability
V.) Lateral view
- Unilateral shoulder examination – look for anterior rounding
- Check curvature of the spine (kyphosis)

Question 24

Palpation

Answer 24

I.) Skin – temperature, tenderness, texture; moisture, and mobility
II.) Soft tissues – tone consistency, mobility, swelling, pulse, tenderness
III.) Bones and soft-tissue attachments – joint lines, bony contours, tenderness

Question 25

Movement

Answer 25

I.) Functional ROM – assesses combined movements. This tells us which movements are available and pain free and which movements need to be addressed.
a.) Combing the back of head (open chain)
b.) Reaching into the back pocket (open chain)
c.) Apley’s Scratch test (p. 1075- Clinical Massage Therapy - Rattray and Luwig & p. 187 - Orthopedic Physical Assessment – 4th Edition Magee) (open chain)
d.) Getting up out of a chair using the armrests (closed chain)
II.) AROM (Flex-Ext, IR-ER, AB-AD, Horizontal AD-AB, Elevation-Depress, Protract-Retract)
a.) All movement should be observed with the most painful movements performed last.
b.) Movements should be purely performed by the shoulder girdle. Watch to make sure the patient doesn’t ‘cheat’ – abduction should not include external rotation otherwise the biceps will be incorporated. Exaggerated movements of the spine should not be included either.
c.) With abduction, a painful arc should be observed. This pain is a result of the ‘pinching’ of inflamed structures under the acromial arch – subacromial bursitis, calcium deposits, or tendinitis of the rotator cuff muscles.
PROM – If passive over pressure wasn’t performed in AROM due to restriction or pain, determine the end feel with PROM of the shoulder complex. Determine if there is a capsular or non-capsular pattern of restriction.
III.) Resisted muscle testing (ISOMETRIC)
a.) General resistance in various movements tested first to isolate which movements are most affected
b.) Various muscles of the shoulder should be resisted isometrically to pin point the exact muscles influenced. Manual muscle and a break test provide objective findings.
c.) RROM with elbow flexion and extension should be included as triceps and biceps also cross the shoulder joint complex
d.) Note if patient complains that isotonic contraction is painful and symptomatic. These movements should also be tested if needed.

Question 26

What is a painful arc and why does it occur?

Answer 26

The first 45-60˚of ABD is painless b/c there is no pinching under the acromial arch.
Abduction of 60-120˚ causes the structures to become pinched and abduction may cease.
If abduction continues, pain diminishes after 120˚ bc the pinched structures have passed under the acromion process and are no longer pinched.
The pain may return in the last 10-20˚ of abduction indicating possible impingement (general pain) or AC/SC joint involvement (specific pain).

Question 27

d.) Reverse Scapulohumeral Rhythm

Answer 27

this is when the scapula moves more than the humerus with abduction. The guest tends to hike the shoulder upward to achieve movement. This is indicative of frozen shoulder.

Question 28

Some quickie tests for scapular winging:

Answer 28

Patient bends elbow, GH flexes to 90˚, face guest and push into elbow posteriorly, grasp ventral surface of the scapula and push dorsally against resistance.
Instruct patient to get into a ‘push-up’ position against the wall to push against the wall – observe if the scapula wings. (hands together, with elbows/forearms)

Question 29

Neurological

Answer 29

we do this testing to confirm or rule out neurological involvement (e.g. spinal nerve root involvement)

• Dermatome, myotome (C4, C5, C6)
• Reflex testing:
  1. C5 – Biceps
  2. C6 – Brachioradialis
  3. C7 - Triceps

Question 30

Referred pain

Answer 30

Pain associated with the shoulder is usually non-specific and is generally felt over the lateral brachial region (with the exception to AC joint lesions). Take note if pain goes past the elbows and into the hands.

Question 31

Special tests

Answer 31

The value and purpose of doing a special test:
 Used to confirm or refute a specific pathology or condition.
 Tells us which structures are involved in an injury or condition.
 RMTs cannot diagnose a condition or pathology but instead, can make strong conclusions (We can say that the objective findings lead to a possible condition).
 Proficient special testing leads to higher reliability.
 Many of the structures involved in different pathologies are inter-related
(ie: impingement syndrome and shoulder instability); the RMT must be able to correlate the history with the appropriate special test and understand what a positive or negative test indicates.
 A positive special test indicates which tissues are affected and determines treatment.
 An RMT must know when performing a special test is appropriate. Eg: it would be inappropriate to perform a shoulder apprehension test with a recent dislocation (10-12 days)

Question 32

Functional Anatomy

Glenohumeral

Answer 32

Osteokinematics-
3 degrees of freedom:
Flex-Ext, AB-AD, ER-IR
Athrokinematics-
Head of humerus= convex
Glenoid fossa = concave
Resting position-
55-70˚ AB & 30˚ horizontal AD
Closed pack position-
Full AB & ER
Capsular pattern of restriction-
ER > AB > IR
ROM and end feel-
Flex-180˚ (0-60˚= GH, 60-180˚= GH, scapula, trunk); firm
Ext-60˚; firm
ER-90˚; firm
IR-70˚; firm
AB-180˚ (0-30˚= GH, 30-180˚= GH, scapula, trunk); firm/hard
Horizontal AB-45˚; firm
Horizontal AD-135˚; firm/soft

Question 33

Functional Anatomy Acromioclavicular

Answer 33

Osteokinematics-3 degrees of freedom:
Elevation-Depression, Protraction-Retraction, Upward rotation-Downward rotation
Athrokinematics-Acromion= concave
Acromial end of clavicle= convex
Resting position-Arm by side with pillow support
Closed pack position- Arm AB to 90˚
Capsular pattern of restriction-Full elevation with associated pain
ROM and end feel-
Elevation/Depression-30˚
Protract/Retraction-50˚
Rotation-50˚
All motions have a capsular firm end feel

Question 34

Functional Anatomy Sternoclavicular

Answer 34

Osteokinematics-3 degrees of freedom:
Elevation-Depression, Protraction-Retraction, Upward rotation-Downward rotation
Athrokinematics-Clavicular notch of manubrium=
Ant/Post- convex
Sup/Inf- concave
Sternal end of clavicle=
Ant/Post- concave
Sup/Inf- convex
Resting position-Arm by side with pillow support
Closed pack position-Arm maximally elevated
Capsular pattern of restriction-Full eleavation with associated pain
ROM and end feel-Elevation/Depression-15˚
Protraction/Retraction-10˚
Rotation-50˚
All motions have a capsular firm end feel