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Questions and Answers
The elbow complex consists of 3 bones and 3 joints.
The elbow complex consists of 3 bones and 3 joints.
False
The humeroulnar joint is the main joint responsible for elbow motion.
The humeroulnar joint is the main joint responsible for elbow motion.
True
Rotation at the elbow complex does not provide any additional mobility for the hand.
Rotation at the elbow complex does not provide any additional mobility for the hand.
False
The distal radioulnar joint is not considered part of the elbow complex.
The distal radioulnar joint is not considered part of the elbow complex.
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Flexion and extension are the only motions permitted at the elbow.
Flexion and extension are the only motions permitted at the elbow.
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The radius and ulna joints together permit rotation around a lateral axis.
The radius and ulna joints together permit rotation around a lateral axis.
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The trochlea of the humerus has a thread-like shape.
The trochlea of the humerus has a thread-like shape.
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The elbow complex has 2 degrees of freedom.
The elbow complex has 2 degrees of freedom.
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The elbow joint is classified as a diarthrodial joint.
The elbow joint is classified as a diarthrodial joint.
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The brachialis is the least effective elbow flexor due to its small cross-sectional area.
The brachialis is the least effective elbow flexor due to its small cross-sectional area.
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The biceps brachii is most active during flexion and pronation.
The biceps brachii is most active during flexion and pronation.
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The primary elbow extensors include the brachioradialis.
The primary elbow extensors include the brachioradialis.
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Optimal stretch of the muscles leads to more powerful contractions.
Optimal stretch of the muscles leads to more powerful contractions.
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The anconeus is primarily responsible for flexing the elbow.
The anconeus is primarily responsible for flexing the elbow.
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Muscles acting on the wrist usually do not affect the elbow joint.
Muscles acting on the wrist usually do not affect the elbow joint.
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The efficiency of the triceps brachii is maximal between 20°-30° of elbow flexion.
The efficiency of the triceps brachii is maximal between 20°-30° of elbow flexion.
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Both the biceps and the triceps are monoarticular muscles.
Both the biceps and the triceps are monoarticular muscles.
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The brachioradialis can cause full flexion regardless of forearm position.
The brachioradialis can cause full flexion regardless of forearm position.
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Isometric contraction of the elbow flexors and extensors near 90° creates an unstable elbow posture.
Isometric contraction of the elbow flexors and extensors near 90° creates an unstable elbow posture.
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The pronator teres is a strong elbow flexor with primary actions at the shoulder joint.
The pronator teres is a strong elbow flexor with primary actions at the shoulder joint.
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The medial head of the triceps brachii is active during unresisted elbow extension.
The medial head of the triceps brachii is active during unresisted elbow extension.
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Maximum isometric torque generation of the triceps occurs at full elbow extension.
Maximum isometric torque generation of the triceps occurs at full elbow extension.
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The activity of the long head of the triceps brachii is not influenced by the position of the shoulder joint.
The activity of the long head of the triceps brachii is not influenced by the position of the shoulder joint.
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The Anconeus assists in both elbow extension and stabilization during supination and pronation.
The Anconeus assists in both elbow extension and stabilization during supination and pronation.
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The flexors and extensors of the forearm activate independently of stress conditions.
The flexors and extensors of the forearm activate independently of stress conditions.
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Heavy resistance activates all three heads of the triceps brachii.
Heavy resistance activates all three heads of the triceps brachii.
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High levels of activity during forearm motions occur only at slow speeds.
High levels of activity during forearm motions occur only at slow speeds.
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The flexor carpi radialis is primarily a wrist flexor and plays a minor role in elbow flexion.
The flexor carpi radialis is primarily a wrist flexor and plays a minor role in elbow flexion.
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The triceps brachii is affected by changes in the position of the elbow and forearm equally.
The triceps brachii is affected by changes in the position of the elbow and forearm equally.
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A total arc of $100°$ of elbow flexion is sufficient for simple tasks.
A total arc of $100°$ of elbow flexion is sufficient for simple tasks.
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Mobility at the elbow complex enhances the stability of the wrist and hand.
Mobility at the elbow complex enhances the stability of the wrist and hand.
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The biceps brachii muscle is innervated by the axillary nerve.
The biceps brachii muscle is innervated by the axillary nerve.
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Forearm rotation is equally divided between pronation and supination.
Forearm rotation is equally divided between pronation and supination.
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The humerus creates close structural relationships with the wrist due to the attachment of hand muscles.
The humerus creates close structural relationships with the wrist due to the attachment of hand muscles.
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The deltoid muscle is innervated by the musculocutaneous nerve.
The deltoid muscle is innervated by the musculocutaneous nerve.
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The main movement at the proximal radio-ulnar joint is translation of the radial head.
The main movement at the proximal radio-ulnar joint is translation of the radial head.
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The annular ligament contributes to the flexibility of the cuff around the radial head.
The annular ligament contributes to the flexibility of the cuff around the radial head.
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During pronation, the radial head becomes orientated transversely with a lateral shift.
During pronation, the radial head becomes orientated transversely with a lateral shift.
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The axis of pronation-supination in the distal radio-ulnar joint is located near the medial edge of the radius.
The axis of pronation-supination in the distal radio-ulnar joint is located near the medial edge of the radius.
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The radial tuberosity lies between the radius and the ulna during supination.
The radial tuberosity lies between the radius and the ulna during supination.
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The capitulo-trochlear groove of the humerus is involved in the gliding movement of the radial head.
The capitulo-trochlear groove of the humerus is involved in the gliding movement of the radial head.
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The quadrate ligament limits the movement of the radial head in both supination and pronation.
The quadrate ligament limits the movement of the radial head in both supination and pronation.
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In the dynamic tripod of prehension, the axis of rotation passes through the lower end of the ulna.
In the dynamic tripod of prehension, the axis of rotation passes through the lower end of the ulna.
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Cubitus valgus influences the obliqueness of the forearm's axis.
Cubitus valgus influences the obliqueness of the forearm's axis.
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The proximal surface of the radial head tilts laterally and distally during pronation.
The proximal surface of the radial head tilts laterally and distally during pronation.
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Study Notes
Elbow Complex Function
- The elbow complex is made up of 3 bones and 4 joints.
- The elbow complex provides mobility for the hand in space.
- It allows the hand to be brought close to the face for eating and grooming or to be placed at a distance from the body equal to the length of the entire upper extremity.
- The elbow complex also provides stability for skilled or forceful movements of the hand.
- The elbow and wrist are linked together to enhance hand function.
Elbow Complex Structure
- The elbow joint is a compound joint that functions as a modified or loose hinge (ginglimus) joint.
- The elbow joint allows for flexion and extension.
- The proximal & distal radioulnar joints function as one joint to provide forearm rotation.
- The radioulnar joints are diarthrodial uniaxial pivot joints (trochoid) and permit rotation (supination and pronation).
Distal Humerus
- The shaft of the humerus ends medially as the trochlea and medial epicondyle.
- The shaft of the humerus ends laterally as the capitulum and lateral epicondyle.
Flexor Muscles
- The primary elbow flexors are:
- Brachialis: The workhorse of the flexors, it has the largest cross-sectional area to generate the greatest force.
- Biceps Brachii: Produces maximal activity when performing flexion and supination simultaneously.
- Brachioradialis: Regardless of forearm position, contraction causes full flexion and rotates the forearm towards the neutral, thumb-up position.
- The secondary assisting synergists for the flexor muscles are Pronator Teres and ECRL.
Extensor Muscles
- The primary elbow extensors are:
- Triceps Brachii: Works as a first-class lever and provides maximal efficiency between 20°-30°.
- Anconeus: Useful for producing “background” joint stability and provides forces that stabilize the ulna during active pronation and supination.
Flexion-Extension Considerations
- Biceps and triceps are polyarticular muscles that produce force across multiple joints.
- When speed is increased, the flexors show moderate activity with a loaded forearm.
- Pronator Teres, as well as the palmaris longus, flexor digitorum superficialis, flexor carpi radialis, and flexor carpi ulnaris, is a weak elbow flexor with primary actions at the radioulnar and wrist joints.
Flexion-Extension Considerations for Extensors
- The activity of the long head of the triceps is affected by changing shoulder joint position.
- The medial and lateral heads of the triceps are not affected by the position of the shoulder.
- Maximum isometric torque generation for the triceps brachii is at a position of 90° of elbow flexion.
- The triceps is active eccentrically to control elbow flexion and concentrically to extend the elbow in a closed kinematic chain, such as in a push-up.
- The triceps act as a stabilizing synergist to prevent flexion of the elbow.
Proximal Radio-Ulnar Joint
- The main movement of the proximal radio-ulnar joint is rotation of the radial head about its axis within the fibro-osseous ring.
- The tension of the quadrate ligament limits movement during supination and pronation.
- The radial head is slightly oval, which explains why the annular cuff of the radial head cannot be bony and rigid.
Foream Mobility
- The cup-shaped surface of the radial head spins with respect to the capitulum humeri.
- The beveled ridge of the radial head glides in contact with the capitulo-trochlear groove of the humerus.
- During pronation, the radial head comes to lie transversely with a lateral shift allowing the radius to move out of the way of the ulna.
Distal Radio-Ulnar Joint
- The axis of pronation-supination extends into the hand along the medial edge of the ulna and the fifth finger while maintaining contact with the table.
- The radius glides and rolls on the ulna.
- The axis of pronation-supination is intermediate in location and passes through the lower end of the radius near the ulnar notch, which is collinear with the axis of the hand (the 3rd finger).
- In this case, not only the position of the radius but also the ulna is changing.
Function of the Elbow Complex
- Most activities of daily living require a combination of motion at both the elbow and radioulnar joints.
- A total arc of ~100° of elbow flexion (between 30° and 130°) and ~100° of forearm rotation (~50° supination and ~50° pronation) is sufficient to accomplish simple tasks.
- Mobility of the elbow complex is necessary for normal functioning.
- Compensations for limited range of motion of the elbow complex happen at the shoulder.
- The mobility afforded the hand by pronation and supination of the forearm is achieved at the expense of stability because the movable forearm is unable to provide a stable base for attachment of the wrist and hand muscles.
- Many of the muscles that act on the wrist and hand are attached on the distal end of the humerus.
- The fact that the wrist and most the extrinsic hand muscles cross the elbow create close structural and functional relationships between the elbow and wrist/hand complexes.
- Anatomically, the hand and wrist muscles help reinforce the elbow joint capsule and contribute to stability of the elbow.
Muscle Innervation and Dermatomes
- Musculocutaneous Nerve (C5-7):
- Coracobrachialis Muscle
- Biceps Brachii
- Brachialis Muscle
- Axillary Nerve (C5-6):
- Deltoid Muscle
- Teres Minor muscle
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Description
Explore the anatomy and function of the elbow complex, including its structure and the role it plays in hand mobility and stability. This quiz covers key components such as bones, joints, and their movements, enhancing your understanding of upper extremity dynamics.
