Upper extremity anatomy
Functional anatomy of the upper extremity
Shoulder region
Movement of the shoulder requires the glenohumeral joint (shoulder joint) and the scapular complex (shoulder girdle) to move together in a pattern called scapulohumeral rhythm. The shoulder region is composed of three primary bones: the humerus, scapula, and clavicle. The humerus and scapula form the glenohumeral joint, and the scapula and clavicle together make up the shoulder girdle. The clavicle articulates with the scapula at the acromioclavicular joint and with the sternum at the sternoclavicular joint. Additionally, movement of the scapula on the thorax contributes to scapulohumeral rhythm required for all shoulder movement.
Primary movements of the shoulder
- Shoulder flexion/extension
- Shoulder elevation/depression
- Shoulder external rotation/internal rotation
- Shoulder abduction/adduction
- Scapular elevation/depression
- Scapular upward rotation/downward rotation
- Scapular abduction/adduction
The glenohumeral joint articulates the humeral head into a concave glenoid fossa. The ligaments that aid in stability are the superior, middle, and inferior glenohumeral ligaments.
- The superior glenohumeral ligaments prevent excessive external rotation and inferior translation.
- The middle glenohumeral ligament prevents excessive external rotation and anterior translation.
- The inferior glenohumeral ligament prevents anterior-inferior dislocation, the anterior portion external rotation, and the posterior portion internal rotation.
The glenohumeral joint has other important anatomical features:
- Labrum - a fibrocartilaginous rim around the glenoid fossa that deepens the socket and improves glenohumeral stability
- Bursae - act as fluid-filled sacs that provide cushioning and friction reduction between tendons, joints, muscles, and bone
- Long head of biceps tendon - originates at the supraglenoid tubercle/superior labrum, courses over the humeral head, and helps depress and stabilize the humeral head anteriorly
The sternoclavicular joint articulates with the sternum and the clavicle via a fibrocartilage. This articulation is the only point of connection between the axial skeleton and the appendicular limbs.
The sternoclavicular joint is essential for maintaining upper limb stability, facilitating movement, and protecting underlying structures. Its unique structure and design allow for a wide range of motion while assisting with breathing.
The acromioclavicular joint connects the scapula to the clavicle, allowing motion of the shoulder, stabilization and movement of the scapula, and stability to the shoulder girdle.
The acromioclavicular joint is stabilized by the acromioclavicular ligament and the coracoclavicular ligament (made up of the conoid and trapezoid ligaments). This joint lies within a small capsule that provides additional support and protection.
The scapulothoracic joint is a non-synovial, physiological joint formed by the interface between the scapula and the thoracic wall, supported by surrounding muscles and bursae rather than a true bony articulation. Its motion works together with the sternoclavicular and acromioclavicular joints, since scapular movement on the thorax requires motion at those joints, and together they produce full shoulder motion.
Elbow region
The elbow region consists of connections of bony structures between the distal humerus and the proximal radius and ulna. Three joints comprise the elbow: humeroulnar, humeroradial, and proximal radioulnar. The distal radioulnar joint works with the proximal radioulnar joint to produce forearm rotation, but it belongs to the forearm/wrist region rather than the elbow itself.
Primary movements of the elbow
- Elbow flexion/extension
- Forearm supination/pronation
The elbow joint has other important anatomical features
- Capsule - a thin structure that surrounds the anterior and posterior components of the joint
- Bursae - fluid-filled sacs that cushion and reduce friction at the elbow joint
Ligaments of the elbow
- Ulnar collateral ligament
- Ligament is triangular in shape, running anteriorly, posteriorly, and obliquely to reinforce the medial humeroulnar joint
- Radial collateral ligament
- Fan-shaped ligament that runs from the lateral epicondyle to the annular ligament, to support the humeroradial joint laterally
- Annular ligament
- Cone-shaped ligament that envelopes the radial head and attaches to the anterior and posterior margins of the radial notch of the ulna; protects the radial head
- Quadrate ligament
- Extends from the radial notch on the ulna surface to the neck of the radius; reinforces the inferior portion of the joint capsule
- Distal radioulnar ligament
- Composed of the anterior and posterior radioulnar ligaments to provide strength to the capsule
Wrist and hand region
The wrist and hand region is composed of the distal radius, the distal ulna, the carpals, the metacarpals, and the phalanges. There are six joints of the wrist and hand: radiocarpal joint, midcarpal joint, carpometacarpal joint (CMC), metacarpophalangeal joint (MCP), proximal interphalangeal joint (PIP), and distal interphalangeal joint (DIP).
Primary movements of the wrist and hand
- Wrist flexion/extension
- Wrist radial deviation/ulnar deviation
- Finger flexion/extension
- Finger abduction/adduction
- Intrinsic finger movement
The wrist and hand joint has other important anatomical features
- Capsule of wrist and hand - provide support to internal structures
- Volar plate - present on the palmar aspect of the MCP, PIP, and DIP to protect joints
- Palmar aponeurosis - sheet of fibrous tissue in the palm that protects underlying tendons and nerves.
- Extensor hood - fibrous connection on the dorsum of the finger that aids in extension of the PIP and DIP
- Nerves - radial, median, and ulnar are the primary nerves of innervation for the wrist and hand
Ligaments of the wrist
- Dorsal radiocarpal
- Limits flexion, pronation
- Radiate
- Stabilizes the hand
- Radial collateral ligament
- Limits ulnar deviation
- Ulnar collateral ligament
- Limits radial deviation
- Palmar ulnocarpal
- Limits extension and supination
- Palmar radiocarpal
- Limits extension and supination through the knuckles
Ligaments of fingers
- Collateral ligaments
- Oriented from the lateral condyle to the distal phalanx and on the lateral volar plate to each metacarpal, PIP, and DIP
- All fibers tighten during flexion, but only volar fibers tighten during extension
- Accessory
- Oriented from the condylar head to the volar plate
- Transverse
- Provide stability linking the MCP joints and reinforcing the anterior capsule
Upper extremity range of motion normals
Shoulder range
- Flexion: 160 - 180 degrees
- Extension: 50 - 60 degrees
- Abduction: 170 - 180 degrees
- Adduction: 50 - 75 degrees
- External rotation: 80 - 90 degrees
- Internal rotation: 60 - 100 degrees
Elbow range
- Flexion: 140 - 150 degrees
- Extension: 0 - 10 degrees
- Supination: 90 degrees
- Pronation: 80 - 90 degrees
Wrist range
- Flexion: 60 - 70 degrees
- Extension: 60 - 75 degrees
- Radial deviation: 15 degrees
- Ulnar deviation: 30 - 45 degrees
MCP range
- Flexion: 85 - 90 degrees
- Extension: 30 - 45 degrees
PIP range
- Flexion: 100 - 115 degrees
- Extension: 0 degrees
DIP range
- Flexion: 80 - 90 degrees
- Extension: 20 degrees
1st CMC range
- Flexion: 45 - 50 degrees
- Abduction: 60 - 70 degrees
- Adduction: 30 degrees
1st MCP range
- Flexion: 50 - 55 degrees
- Extension: 0 degrees
1st IP range
- Flexion: 85 - 90 degrees
- Extension: 0 - 5 degrees
This anatomical foundation sets up the special tests and clinical conditions covered in the chapters that follow, including comparing clinical presentation and interventions for the upper extremity.