Chapter 4 Shoulder Girdle Notes PDF

**Chapter 4** **Shoulder Girdle Notes** **Overview** - **Shoulder Girdle** ≠ Shoulder Joint (Glenohumeral Joint) - **Shoulder Girdle**: Scapula (shoulder blade) + Clavicle (collarbone) - **Glenohumeral Joint**: Ball-and-socket joint between humerus and scapula (gle...

**Chapter 4** **Shoulder Girdle Notes** **Overview** - **Shoulder Girdle** ≠ Shoulder Joint (Glenohumeral Joint) - **Shoulder Girdle**: Scapula (shoulder blade) + Clavicle (collarbone) - **Glenohumeral Joint**: Ball-and-socket joint between humerus and scapula (glenoid fossa) - **Key Bones** - **Sternum (Manubrium)**: Connects clavicle to axial skeleton. - **Clavicle (Collarbone)**: Connects sternum to scapula. - **Scapula (Shoulder Blade)**: Glides along rib cage, moves with clavicle. **Ligaments of the Shoulder Girdle** - **Acromioclavicular Ligament** - **Trapezoid Ligament** - **Conoid Ligament** - **Costoclavicular Ligament** - **Anterior Sternoclavicular Ligament** These ligaments link the clavicle, scapula, and sternum, allowing **coordinated movement** of the shoulder girdle. **Key Bony Landmarks (Scapula)** 1. **Coracoid Process** (Anterior) - Attachment for muscles that elevate and depress the scapula. 2. **Acromion Process** (Posterior) - Forms the **Acromioclavicular (AC) Joint** with the clavicle. - Common site for injuries (e.g., AC joint separation). 3. **Glenoid Fossa (Cavity)** - Articulates with humerus to form the **Glenohumeral Joint** (ball-and-socket). 4. **Borders and Angles** - **Medial Border**: Attachment for muscles that pull the scapula together. - **Lateral Border**: Important for muscle leverage. - **Inferior Angle**: Rotation point for muscles. **Key Bony Landmarks (Clavicle)** - **Sternal End**: Articulates with the manubrium of the sternum at the **Sternoclavicular Joint**. - **Acromial End**: Articulates with the acromion process at the **Acromioclavicular Joint**. **Clavicle Movement**: - Rotates front to back and moves up and down during shoulder motions. **Joints of the Shoulder Girdle** 1. **Sternoclavicular Joint** - Primary link between the axial skeleton and the upper extremity. - Allows rolling and pivoting of the clavicle. 2. **Acromioclavicular (AC) Joint** - Provides some independent motion for the scapula relative to the clavicle. **Shoulder Girdle Movements** - **Elevation/Depression**: Upward and downward scapular motion. - **Protraction/Retraction**: Lateral (side-to-side) motion. - **Rotation**: Scapula rotates along the rib cage. **Key Points**: - Movement at the scapula is linked to movement at both the **sternoclavicular** and **acromioclavicular joints**. - Joint motion at these points allows the scapula to move freely along the rib cage. **Shoulder Girdle Movements & Muscle Actions** All right, now that we've covered the anatomy and movement points of the shoulder girdle, let's dive into specific movements and the muscles that cause them. An important thing to point out here is that **shoulder girdle movement is essentially scapular movement**. You won't find many cases where muscles pulling on the clavicle alone move the entire girdle. In general, **scapular movement drives the shoulder girdle**, and it's the muscles moving the scapula that lead to clavicular movement. So, we'll focus on the **muscles responsible for scapular motion**. **Scapular Movements:** Let's break down the primary movements of the scapula with their official names: 1. **Elevation** -- Moves the scapula superiorly (straight up). 2. **Depression** -- Moves the scapula inferiorly (straight down). 3. **Abduction (Protraction)** -- Moves the scapula laterally away from the midline (toward the side of the body). 4. **Adduction (Retraction)** -- Moves the scapula medially toward the spinal column (pinching the shoulder blades together). But wait, there's more: 5. **Upward Rotation** -- The **inferior angle** of the scapula moves laterally and upward. This happens when you raise your arm overhead. 6. **Downward Rotation** -- The **inferior angle** moves inferomedially (back toward the spinal column) when the arm returns to your side. **Tips for Recognizing Rotations:** When identifying upward or downward rotation, **always focus on the inferior angle** of the scapula. If it moves laterally and upward, that's **upward rotation**. If it moves back toward the spine, that's **downward rotation**. **Movements in Action:** 1. **Abduction (Protraction)** -- The scapula moves laterally away from the spinal column. Think of this as \"pushing forward,\" like when you reach out for something. 2. **Adduction (Retraction)** -- The scapula moves medially toward the spinal column, like when you pinch your shoulder blades together. 3. **Elevation** -- The scapula moves straight up (shoulder shrug). 4. **Depression** -- The scapula moves straight down (returning from an elevated position). For **upward and downward rotation**, watch how the inferior angle swings when the arm raises and lowers. During **upward rotation**, the glenoid fossa tilts upward, and the inferior angle moves superolaterally. **Downward rotation** is the reverse---bringing the inferior angle back inferomedially. **Scapular vs. Shoulder Joint Muscles:** One key thing to remember: **Scapular movement is separate from glenohumeral (shoulder joint) movement.** - Different muscle groups handle scapular movements vs. shoulder joint (glenohumeral) movements. - For example, muscles that cause **upward rotation** of the scapula aren't responsible for **arm abduction** at the glenohumeral joint, even though both actions often happen together. Scapular stabilization is critical for proper shoulder joint function. When the shoulder girdle isn't stable, shoulder joint movements can become dysfunctional, leading to impingements and other issues. These stabilizing muscles form a strong base for the shoulder joint to move through its full range of motion. Would you like this in a more visual format, with diagrams showing the movements and key muscles? I could also add bullet points for muscles if you want to segue into that next! **Shoulder Girdle Movements: Key Notes** **Main Concept** - Shoulder girdle movement = **scapular movement** (not much movement driven by the clavicle). - Muscles moving the scapula also cause shoulder girdle movement. - **Focus: Scapular muscles and their role in movement.** **Scapular Movements** 1. **Elevation** -- Scapula moves upward (superiorly). - Example: Shoulder shrug. 2. **Depression** -- Scapula moves downward (inferiorly). - Example: Returning from a shoulder shrug. 3. **Abduction (Protraction)** -- Scapula moves laterally away from the midline. - Example: Reaching forward. 4. **Adduction (Retraction)** -- Scapula moves medially toward the spine. - Example: Pinching shoulder blades together. 5. **Upward Rotation** -- Inferior angle of scapula moves superolaterally. - Example: Raising the arm overhead. 6. **Downward Rotation** -- Inferior angle moves inferomedially (toward the spine). - Example: Lowering the arm back to the side. **Rotation Tip:** - **Focus on the inferior angle** to identify upward vs. downward rotation. **Movement Summary in Action** - **Abduction (Protraction):** Scapula moves laterally (away from the spine). - **Adduction (Retraction):** Scapula moves medially (toward the spine). - **Elevation:** Scapula moves upward. - **Depression:** Scapula moves downward. - **Upward Rotation:** Inferior angle moves laterally/upward. - **Downward Rotation:** Inferior angle moves medially/downward. **Scapular Muscles vs. Glenohumeral Muscles** - **Separate muscle groups** handle scapular and shoulder joint (glenohumeral) movements. - **Scapular stabilization** is crucial for proper shoulder joint function. - Weak or unstable scapular muscles → Dysfunctional shoulder movement and impingement risks. - **Scapular movement often occurs alongside shoulder joint movement** (but they are caused by different muscles). **Shoulder Girdle Movements: Key Notes** **Main Concept** - Shoulder girdle movement = **scapular movement** (not much movement driven by the clavicle). - Muscles moving the scapula also cause shoulder girdle movement. - **Focus: Scapular muscles and their role in movement.** **Scapular Movements** 1. **Elevation** -- Scapula moves upward (superiorly). - Example: Shoulder shrug. 2. **Depression** -- Scapula moves downward (inferiorly). - Example: Returning from a shoulder shrug. 3. **Abduction (Protraction)** -- Scapula moves laterally away from the midline. - Example: Reaching forward. 4. **Adduction (Retraction)** -- Scapula moves medially toward the spine. - Example: Pinching shoulder blades together. 5. **Upward Rotation** -- Inferior angle of scapula moves superolaterally. - Example: Raising the arm overhead. 6. **Downward Rotation** -- Inferior angle moves inferomedially (toward the spine). - Example: Lowering the arm back to the side. **Rotation Tip:** - **Focus on the inferior angle** to identify upward vs. downward rotation. **Movement Summary in Action** - **Abduction (Protraction):** Scapula moves laterally (away from the spine). - **Adduction (Retraction):** Scapula moves medially (toward the spine). - **Elevation:** Scapula moves upward. - **Depression:** Scapula moves downward. - **Upward Rotation:** Inferior angle moves laterally/upward. - **Downward Rotation:** Inferior angle moves medially/downward. **Scapular Muscles vs. Glenohumeral Muscles** - **Separate muscle groups** handle scapular and shoulder joint (glenohumeral) movements. - **Scapular stabilization** is crucial for proper shoulder joint function. - Weak or unstable scapular muscles → Dysfunctional shoulder movement and impingement risks. - **Scapular movement often occurs alongside shoulder joint movement** (but they are caused by different muscles). **Shoulder Girdle Muscles Notes** **General Overview:** - **5 primary muscles** involved in shoulder girdle movements. - **Origins:** Axial skeleton - **Insertions:** Scapula and/or clavicle - **Key Note:** These muscles **do not attach to the humerus** and do **not cause shoulder joint (glenohumeral) actions**. **Importance:** - Provide **dynamic stability** of the scapula for complex shoulder joint movements (throwing, batting, blocking). - Proper shoulder girdle movement is essential for overhead activities and injury prevention. **Primary Muscles of the Shoulder Girdle:** 1. **Trapezius (Upper, Middle, Lower Fibers)** - **Actions:** - **Upper fibers:** Elevation, head extension/rotation - **Middle fibers:** Retraction (adduction) and upward rotation - **Lower fibers:** Depression, upward rotation - **Key Role:** Involved in most scapular movements, especially **upward rotation and retraction**. 2. **Levator Scapulae** - **Action:** Elevation of the scapula (e.g., shoulder shrugging). - **Mnemonic:** \"Levator\" = elevator → lifts the scapula. 3. **Rhomboids (Major and Minor)** - **Actions:** Retraction (adduction), downward rotation, slight elevation - **Key Role:** Pull scapula toward the spine and stabilize it during rowing movements. 4. **Serratus Anterior** - **Actions:** Protraction (abduction), upward rotation - **Key Role:** Prevents scapular winging and allows overhead movements without impingement. - **Exercise Example:** Scapular push-ups target serratus anterior. 5. **Pectoralis Minor** - **Actions:** Depression, protraction (abduction), downward rotation - **Key Role:** Stabilizes and moves the scapula anteriorly. - **Exercise Example:** Scapular dips 6. **Subclavius** - **Actions:** Stabilizes sternoclavicular joint, assists with depression of the scapula via the clavicle. **Key Movements and Muscle Contributions:** **1. Scapular Elevation** - **Muscles:** Levator scapulae, upper trapezius, middle trapezius - **Example:** Shoulder shrug **2. Scapular Retraction (Adduction)** - **Muscles:** Middle trapezius, lower trapezius, rhomboids - **Example:** Seated row exercise **3. Scapular Protraction (Abduction)** - **Muscles:** Serratus anterior, pectoralis minor - **Example:** Scapular push-up **4. Upward Rotation** - **Muscles:** Serratus anterior, middle trapezius, lower trapezius - **Example:** Overhead arm movement (reaching up) **5. Downward Rotation** - **Muscles:** Rhomboids, pectoralis minor - **Example:** Lat pulldown exercise **6. Scapular Depression** - **Muscles:** Lower trapezius, pectoralis minor, subclavius - **Example:** Scapular dips **Important Functional Notes:** - **Serratus Anterior Dysfunction** → Scapular winging, increased risk of shoulder impingement. - **Trapezius Dysfunction** → Poor scapular control, limited upward rotation, and shoulder instability. - **Pectoralis Minor** → Often tight in individuals with poor posture, contributing to scapular protraction and forward shoulder posture.