In Depth Notes on the Glenohumeral Joint

Overview of the Glenohumeral Joint

• The lecture focuses on the glenohumeral joint (shoulder joint).
• Key areas covered: Osteology, Arthrology, and Muscle Anatomy.

Glenohumeral Joint Structure

• Composed of: Pectoral girdle (clavicle and scapula) and humerus.
• Joint Type: Ball and socket joint, most mobile joint in human body.
• Trade-Off: High mobility vs. reduced stability due to shallow socket of glenoid fossa.

Comparison with Hip Joint

• Mobility: Glenohumeral joint allows extensive arm movements (e.g., reaching high, lifting).
• Stability: Unlike the hip (deep socket for stability), the shallowness of the shoulder socket requires stabilization from surrounding muscles and structures.

Joints of the Pectoral Girdle

• Three main joints:
  • Sternoclavicular Joint (SC): Clavicle meets sternum.
  • Acromioclavicular Joint (AC): Clavicle meets acromion of scapula.
  • Scapulothoracic Joint: Scapula moves over thorax; important for arm movement.

Scapula Key Features

• Anterior View:

  • Subscapular fossa: Bowl-like structure supporting muscles.
  • Coracoid process: Hook-like projection for muscle attachments (e.g., pectoralis minor).

• Posterior View:

  • Spine of scapula: Palpable ridge separating supraspinous and infraspinous fossae.
  • Acromion: Lateral extension of spine, forms articulation point with clavicle.

• Lateral View:

  • Glenoid fossa: Shallow socket where the humerus head articulates, forming the glenohumeral joint.

Humerus Key Features

• Structure:

  • Long bone with a head, neck (anatomical neck), and shaft (diaphysis).

• Proximal Features:

  • Head: Covered in articular cartilage for smooth movement within glenoid fossa.
  • Greater and Lesser Tubercle: Raised areas for muscle attachment (e.g., greater tubercle is lateral, lesser is anterior).
  • Intertubercular groove: Space between tubercles, containing tendons (e.g., biceps brachii).
  • Surgical neck: Most common fracture site, located distal to the anatomical neck.
  • Deltoid tuberosity: Mid-shaft area for deltoid muscle insertion.

• Radial groove:

  • Located on posterior aspect, houses the radial nerve; important for understanding nerve pathways.

Importance of Connections

• Synergistic action: Muscle movements at the shoulder joint (pectoralis major, rotator cuff) are enhanced by movements in the scapulothoracic joint.
• Understanding anatomy is crucial for comprehending muscle function and movements in upper limb activities.