Joints

Anatomy of the Elbow Joint

  • Posterior Aspect

    • Thick along the outside margin.

    • Strong intrinsic ligaments prevent side-to-side movements or hyperextension.

  • Flexion and Extension

    • Flexion: standard bending movement.

    • Extension: straightening movement.

    • Hyperextension: occurs when the elbow bends backward beyond its normal range (e.g., elbow bending too far back).

  • Ligaments Involved

    • Ulnar Collateral Ligament

    • Injury Risk: Often injured from frequent forceful extensions of the forearm (common in baseball pitchers).

    • Surgery: Tommy John surgery addresses injuries associated with this ligament.

    • Radial Collateral Ligament

    • Provides lateral stability to the elbow joint.

  • Collateral Ligaments

    • Both the ulnar and radial collateral ligaments provide stability and prevent hyperextension.

  • Annular Ligament

    • Located around the head of the radius.

    • Secures the radial head into the elbow joint, articulating with the radial notch of the ulna at the proximal radioulnar joint.

    • Important for maintaining joint stability but is not part of the synovial joint of the elbow.

Types of Joints in the Elbow Region

  • Proximal Radioulnar Joint

    • Functions as a pivot joint, allowing for pronation and supination of the forearm.

    • Movement Definitions:

    • Supination: Holding a bowl of soup (palm up).

    • Pronation: Turning the palm downward.

  • Nursemaid's Elbow (Radial Head Subluxation)

    • Common in children due to ligaments still developing.

    • Occurs when the head of the radius slips out of the annular ligament, often caused by swinging a child.

Joints of the Hand

  • Types of Joints

    • Carpal Bones: Allow for gliding or planar movement with limited mobility.

    • Saddle Joint: Between the trapezium and the first metacarpal (thumb), enabling unique opposition movements.

    • Metacarpophalangeal Joints:

    • Classified as condyloid joints, allowing back-and-forth movements, adduction, and abduction.

    • Interphalangeal Joints:

    • Classified as hinge joints allowing flexion and extension only (similar to the elbow).

The Hip Joint

  • Type of Joint

    • Ball-and-socket joint (like the shoulder).

    • Components:

    • Joint capsule, synovial membrane, and articular cavity.

    • Synovial fluid provides lubrication for smooth movement.

    • Ligament of the Head of the Femur:

    • This small ligament carries an artery to the femoral head but does not stabilize the joint.

  • External Ligaments

    • Iliofemoral Ligament

    • Pubofemoral Ligament

    • Ischiofemoral Ligament

    • Stabilize against hyperextension, arranged to enhance stability of the hip joint.

  • Dislocation Risks

    • Weaker posterior and inferior aspects are more prone to dislocation, often occurring during high-impact activities (e.g., motor vehicle accidents).

  • Articular Cartilage

    • Essential for smooth movement; trauma or blood flow interruption can lead to degeneration or arthritis.

The Knee Joint

  • Overall Characteristics

    • Largest and most complex joint in the body, functions as a modified hinge joint.

    • Differences in stability between anterior (less complete) and posterior (more complete) sides, influencing injury risk.

  • Articulations in the Knee Joint

    • Femoral Patellar Joint: Between femur and patella.

    • Medial Tibiofemoral Joint: Between femur and tibia.

    • Lateral Tibiofemoral Joint: Also between femur and tibia.

  • Movement

    • Provides flexion and extension; slight medial rotation occurs when the knee achieves full extension to lock into a stable position.

  • Menisci

    • Fibrocartilaginous pads absorb shock and cushion the joint, but have poor blood supply, leading to slow healing.

  • Knee Ligaments

    • Extracapsular Ligaments:

    • Lateral Collateral Ligament (LCL)

    • Medial Collateral Ligament (MCL)

    • Stabilize against side-to-side movements.

    • Intracapsular Ligaments:

    • Anterior Cruciate Ligament (ACL) - prevents anterior sliding of the tibia.

    • Posterior Cruciate Ligament (PCL) - prevents anterior sliding of the femur.

  • Common Injuries

    • “Unhappy triad” refers to a common sports injury involving tears in the MCL, medial meniscus, and ACL.

The Ankle Joint

  • Anatomy

    • Inferior ends of tibia and fibula articulate with the talus of the foot, functioning as a hinge joint.

  • Movement Types

    • Dorsiflexion: Drawing toes upward towards knees.

    • Plantar Flexion: Pointing toes downward.

  • Stabilizing Ligaments

    • Anterior Talofibular Ligament

    • Calcaneofibular Ligament

    • Posterior Talofibular Ligament

    • Prevent excessive movement of the talus and protect from inversion and eversion injuries.

  • Medial Deltoid Ligament

    • Shaped like a triangle, prevents anterior and posterior slippage of the talus.

Arches of the Foot

  • Importance

    • Arches absorb shock, support body weight, and provide flexibility, strength, and balance.

  • Arch Types

    • Medial Longitudinal Arch

    • Runs from heel to big toe; the highest arch crucial for shock absorption.

    • Keystone: Talus bone.

    • Lateral Longitudinal Arch

    • Runs along the outer edge from heel to little toe; lower and provides stability.

    • Keystone: Cuboid bone.

    • Transverse Arch

    • Runs across the midfoot.

    • Distributes weight evenly; Keystone: Unknown, possibly navicular bone.

Quiz Preparation Instructions

  • Quiz Details

    • Quiz date: Next Wednesday at 8 AM in the tutorial room.

    • Format: 20 multiple choice questions, 35 minutes.

    • Materials: Bring photo ID, avoid distractions (bags, phones, smartwatches).

  • Quiz Protocol

    • Fill out Scantron sheets correctly (name, student number, test version).

    • Stay seated for the duration of the quiz, and raise your hand for assistance.

    • No talking or disruption allowed during the quiz.

  • Content Covered

    • Quiz covers material on appendicular and axial skeletons, along with joint structures discussed today.