39 Questions
What is the primary function of the elbow complex?
To provide stability for the use of the wrist and hand
How many bones make up the elbow joint?
Three bones: humerus, radius, and ulna
What type of joint is the humero-radial joint, due to the presence of the annular ligament?
Pivot joint
What type of joint is the humero-ulnar joint?
Modified hinge joint
What is the main function of the proximal radioulnar joint?
Pronation and supination of the forearm
What is the degree of freedom of motion in the elbow joint?
1 degree of freedom
What is the purpose of the proximal radio-ulnar joint?
To achieve pronation and supination of the forearm
Which of the following muscles is an extensor of the elbow?
Triceps
What type of ligament connects the radius to the ulna?
Annular ligament
What is the characteristic of an open kinematic chain?
Distal segment is free to move
When does the humero-radial joint make contact?
During elbow flexion > 90dg
In a closed kinematic chain, which segment performs the movement?
Humerus
What type of movement occurs in an open kinematic chain?
Roll and glide in the same direction
What is the relationship between convex and concave movement in the context of roll and glide?
They move in opposite directions
What type of kinematic chain is the humero-radial joint and humero-ulnar joint an example of?
Open kinematic chain
During flexion, which direction does the glide/slide movement occur in the osteokinematics of the elbow joint?
Posterior
What is the term for the rotational movement that occurs when the distal end of the radius moves over the distal end of the ulna?
Pronation and supination
In the anatomical position, what is the orientation of the forearm?
Supine
What is the term for the study of the movement of bones?
Osteokinematics
What is the pivot joint formed by in the context of pronation and supination?
The circular head of the radius, the radial groove of the ulna, and the annular ligament
What is the movement of the forearm in pronation in the anatomical position?
The palm is facing posteriorly
Which muscle is responsible for supination?
Biceps Brachii
What is the average carrying angle in males?
5 to 10 degrees
What contributes to the efficient positioning of the hand for various tasks?
The carrying angle
Why is the carrying angle important?
It helps to keep the hand away from the body
Which ligament's tension limits pronation?
Annular ligament
What is the role of the pronator teres muscle?
Pronation
What is the result of the carrying angle?
The hand is positioned away from the body
What muscle is responsible for pronation?
Pronator teres and Pronator Quadratus
What is the movement of the forearm in pronation in the anatomical position?
The palm is facing posteriorly
Which muscle is responsible for supination?
Biceps brachii
What limits pronation?
Tension of the posterior fibers of the triangular ligament
What is the average carrying angle in females?
10 to 15 degrees
What is the purpose of the carrying angle?
To keep the hand away from the body, providing clearance during activities
Which muscle is responsible for pronation?
Pronator teres
What type of movement occurs in the osteokinematics of pronation and supination?
Rolling and gliding
What is the result of the carrying angle?
Efficient positioning of the hand for various tasks
What ligament's tension limits pronation?
Annular ligament
What is the orientation of the forearm in the anatomical position?
Palm facing anteriorly
Study Notes
Elbow Biomechanics
- The elbow complex consists of the elbow joint and the forearm, working together to position the hand and provide stability for wrist and hand use.
- The elbow joint is a uniaxial, diarthrodial (synovial) hinge joint with 1 degree of freedom of motion in the sagittal plane.
Structure of the Elbow Joint
- The elbow joint is composed of three bones: humerus, radius, and ulna.
- Articulations of the elbow joint include:
- Humeroulnar joint
- Humeroradial joint (no contact until elbow flexion >90°)
- Proximal radio-ulnar joint
Humeroulnar Joint
- Modified hinge joint with 1 degree of freedom: flexion/extension
- "Modified" because the ulna experiences slight axial rotation and side-to-side motion
Humeroradial Joint
- "Mortar and pestle" joint with a "ball and socket" surface
- Behaves like a "pivot" joint due to the presence of the annular ligament, which anchors the radius to the ulna
- Radial head "pivots" around the humeral capitulum
Proximal Radioulnar Joint
- Not part of the hinge joint
- Involved in pronation and supination of the forearm
- Pivot joint (rotation around an axis)
Muscles of the Elbow Joint
- Anterior: Biceps Brachii, Brachioradialis, Brachialis (flexors)
- Posterior: Triceps, Anconeus (extensors)
Ligaments of the Elbow Joint
- Medial collateral ligament (MCL) or Ulnar collateral ligament
- Lateral collateral ligament (LCL) or Radial collateral ligament
- Valgus instability test
- Varus instability test
Kinematics
- Open Kinematic Chain:
- Distal segment is free to move on the proximal segment
- Ulna and radius move on top of the humerus
- Concave on convex movement: roll and glide in the same direction
- Closed Kinematic Chain:
- Distal segment is fixed, and the proximal segment performs the movement
- Radius and ulna are fixed, and the only way to execute movement is to move the humerus
- Convex on concave movement: roll and glide in opposite directions
Extension Kinematics
- Humeroradial joint: open kinematic chain
- Humeroulnar joint: open kinematic chain
- Summary:
- Osteokinematics: glide/slide, roll
- Flexion: posterior glide, anterior roll
- Extension: posterior glide, anterior roll
Arthrokinesis of Pronation and Supination
- Rotational movements occurring at the proximal radioulnar joint
- Pronation: distal end of the radius moves over the distal end of the ulna by rotating the radius in the pivot joint
- Supination: rotation of the forearm so that the palm is facing upwards
Osteokinematics of Pronation and Supination
- Pronation and supination are easily visualized when the elbow is flexed at 90°
- Supination: palm of the hand is facing upwards
- Pronation: palm of the hand is facing downwards
- In the anatomical position, the forearm is in the supine position
- Pronation in the anatomical position: movement of the forearm so that the palm is facing posteriorly
Kinetics: Pronation/Supination Muscles
- Supination: Supinator, Biceps Brachii
- Pronation: Pronator teres, Pronator Quadratus
Carrying Angle
- Angle formed between the long axis of the humerus and the long axis of the forearm when the arm is in the anatomical position
- Average carrying angle:
- Males: 5 to 10 degrees
- Females: 10 to 15 degrees
- Importance:
- Helps to keep the hand away from the body, providing clearance during activities
- Contributes to the efficient positioning of the hand for various tasks
Elbow Biomechanics
- The elbow complex consists of the elbow joint and the forearm, working together to position the hand and provide stability for wrist and hand use.
- The elbow joint is a uniaxial, diarthrodial (synovial) hinge joint with 1 degree of freedom of motion in the sagittal plane.
Structure of the Elbow Joint
- The elbow joint is composed of three bones: humerus, radius, and ulna.
- Articulations of the elbow joint include:
- Humeroulnar joint
- Humeroradial joint (no contact until elbow flexion >90°)
- Proximal radio-ulnar joint
Humeroulnar Joint
- Modified hinge joint with 1 degree of freedom: flexion/extension
- "Modified" because the ulna experiences slight axial rotation and side-to-side motion
Humeroradial Joint
- "Mortar and pestle" joint with a "ball and socket" surface
- Behaves like a "pivot" joint due to the presence of the annular ligament, which anchors the radius to the ulna
- Radial head "pivots" around the humeral capitulum
Proximal Radioulnar Joint
- Not part of the hinge joint
- Involved in pronation and supination of the forearm
- Pivot joint (rotation around an axis)
Muscles of the Elbow Joint
- Anterior: Biceps Brachii, Brachioradialis, Brachialis (flexors)
- Posterior: Triceps, Anconeus (extensors)
Ligaments of the Elbow Joint
- Medial collateral ligament (MCL) or Ulnar collateral ligament
- Lateral collateral ligament (LCL) or Radial collateral ligament
- Valgus instability test
- Varus instability test
Kinematics
- Open Kinematic Chain:
- Distal segment is free to move on the proximal segment
- Ulna and radius move on top of the humerus
- Concave on convex movement: roll and glide in the same direction
- Closed Kinematic Chain:
- Distal segment is fixed, and the proximal segment performs the movement
- Radius and ulna are fixed, and the only way to execute movement is to move the humerus
- Convex on concave movement: roll and glide in opposite directions
Extension Kinematics
- Humeroradial joint: open kinematic chain
- Humeroulnar joint: open kinematic chain
- Summary:
- Osteokinematics: glide/slide, roll
- Flexion: posterior glide, anterior roll
- Extension: posterior glide, anterior roll
Arthrokinesis of Pronation and Supination
- Rotational movements occurring at the proximal radioulnar joint
- Pronation: distal end of the radius moves over the distal end of the ulna by rotating the radius in the pivot joint
- Supination: rotation of the forearm so that the palm is facing upwards
Osteokinematics of Pronation and Supination
- Pronation and supination are easily visualized when the elbow is flexed at 90°
- Supination: palm of the hand is facing upwards
- Pronation: palm of the hand is facing downwards
- In the anatomical position, the forearm is in the supine position
- Pronation in the anatomical position: movement of the forearm so that the palm is facing posteriorly
Kinetics: Pronation/Supination Muscles
- Supination: Supinator, Biceps Brachii
- Pronation: Pronator teres, Pronator Quadratus
Carrying Angle
- Angle formed between the long axis of the humerus and the long axis of the forearm when the arm is in the anatomical position
- Average carrying angle:
- Males: 5 to 10 degrees
- Females: 10 to 15 degrees
- Importance:
- Helps to keep the hand away from the body, providing clearance during activities
- Contributes to the efficient positioning of the hand for various tasks
Learn about the functions of the elbow complex, including shortening and lengthening of the arm, providing stability for wrist and hand use, and its relation to the forearm joints. Understand the mechanics of pronation and supination.
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