Elbow Joint Anatomy and Functions

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Questions and Answers

At 0 degrees shoulder elevation, which head of the triceps brachii is most active?

Accessory head

Long head (correct)

Lateral head

Medial head

What is the role of the brachialis muscle at the elbow joint?

Adductor

Extensor

Flexor (correct)

Rotator

Which factor does NOT affect the moment arm of the biceps brachii?

Position of the wrist (correct)

Angle of shoulder elevation

Forearm position

Magnitude of resistance

What type of muscle is the brachialis classified as?

Mobility muscle Signup and view all the answers

When is the moment arm of the brachialis greatest?

At 100 degrees of flexion Signup and view all the answers

Which muscle has the largest volume among the flexors at the elbow joint?

Biceps brachii Signup and view all the answers

Which statement correctly describes the triceps brachii muscle at 90 degrees shoulder elevation?

Medial head is most active Signup and view all the answers

What is the primary action of the biceps brachii?

Flexion Signup and view all the answers

What is the primary function of the elbow joint?

To provide mobility for placing the hand in space and stability for forceful movements Signup and view all the answers

What classification best describes the elbow joint?

Modified or loose hinge joint with one degree of freedom Signup and view all the answers

Which position is considered the closed-pack position of the elbow?

Full extension Signup and view all the answers

Which ligament primarily restrains valgus stress at the elbow?

Medial collateral ligament Signup and view all the answers

What is the functional significance of the carrying angle at the elbow?

It results from the configuration of articulating surfaces Signup and view all the answers

What is the range of motion for active elbow flexion?

135°-145° Signup and view all the answers

Which of the following describes situations leading to active insufficiency of multijoint muscles at the elbow?

The muscle is shortened and can’t apply sufficient force. Signup and view all the answers

Which ligaments stabilize the elbow against varus stress?

Radial collateral ligament and lateral collateral ligament Signup and view all the answers

What does the term 'open chain activities' at the elbow refer to?

Activities where the distal segment is free to move Signup and view all the answers

How is the joint capsule of the elbow characterized?

Loose and large with weak anteriorly and posteriorly Signup and view all the answers

What is the primary role of the ulnar collateral ligament (UCL) during elbow flexion?

To guide joint motion throughout flexion Signup and view all the answers

Which condition is a potential source of stress on the lateral collateral ligament?

Posterior dislocation of the elbow Signup and view all the answers

What causes the variation in the carrying angle between genders?

Differences in bone structure and anatomy Signup and view all the answers

What happens to the carrying angle at 30 degrees of elbow flexion?

It becomes less pronounced Signup and view all the answers

At which angle does the lateral head of the triceps brachii primarily become active during elbow extension?

Beyond 90 degrees Signup and view all the answers

What characteristic best distinguishes the biceps brachii in terms of joint involvement?

It crosses two joints Signup and view all the answers

Which of the following statements about the brachialis muscle is accurate?

It remains unaffected by shoulder position. Signup and view all the answers

Where is the moment arm of the biceps brachii the greatest?

Between 80°-100° of flexion Signup and view all the answers

Which muscle would be considered a mobility muscle that performs elbow flexion at all contraction types?

Brachialis Signup and view all the answers

How does the biceps brachii's activation depend on the magnitude of resistance?

More resistance results in more activation. Signup and view all the answers

What defines the moment arm of the brachialis at 100° of flexion?

It is the greatest. Signup and view all the answers

During isotonic contractions of the elbow, which factor primarily influences the force output of the biceps brachii?

Forearm position Signup and view all the answers

What is the primary role of the lateral collateral ligament (LCL) at the elbow?

Stabilizes against varus stress Signup and view all the answers

Which muscle group's co-contraction aids in the stability of the elbow joint?

Elbow flexors and extensors Signup and view all the answers

At what degree of elbow flexion does the carrying angle disappear?

At 30 degrees Signup and view all the answers

What physical characteristic predominantly influences the normal carrying angle?

Configuration of the articulating surfaces Signup and view all the answers

Which phrase best describes the elbow as a modified hinge joint?

Allows flexion, extension, and slight axial rotation Signup and view all the answers

What type of joint capsule is associated with the elbow joint?

A single joint capsule that is large, loose, and weak anteriorly Signup and view all the answers

Which of the following is true about the closed-packed position of the elbow joint?

It occurs when the elbow is fully extended. Signup and view all the answers

What does active insufficiency mean in the context of multijoint muscles at the elbow?

The muscle is shortened and cannot generate enough force. Signup and view all the answers

Which structure primarily guides joint motion throughout the flexion and extension at the elbow?

The anterior ulnar collateral ligament Signup and view all the answers

Which statement accurately describes the flexion range of motion at the elbow joint?

Passive range of motion exceeds that of active range. Signup and view all the answers

In what ways does the medial collateral ligament (UCL) function at the elbow during flexion?

Restrains valgus stress and guides motion Signup and view all the answers

What anatomical feature significantly affects the medial epicondyle's placement in relation to the carrying angle?

The more caudal extension of the medial epicondyle Signup and view all the answers

Which factor contributes to the normal variation in carrying angle observed between genders?

Differences in the morphology of the medial and lateral epicondyles Signup and view all the answers

Study Notes

Elbow Joint Functions

The elbow is a compound joint that functions both as a modified hinge joint with one degree of freedom.
It provides mobility for positioning the hand, and stability for forceful movements.

Elbow Joint Structure

The elbow joint is made up of three articulations: humeroulnar, humeroradial, and proximal radioulnar.
The articulating surfaces include the humerus, radius, and ulna.
The joint capsule surrounds all three articulations and is fairly large but weak anteriorly and posteriorly.
The capsule is reinforced by the ulnar collateral ligament (UCL) and the radial collateral ligament (RCL).

Elbow Joint Ligaments

The medial collateral ligament (UCL) is fused with the common flexor tendon and is important for resisting valgus stress at elbow flexion between 20-120°.
The lateral collateral ligament (LCL) is fused with the common extensor tendon and is important for resisting varus stress and combined varus and supination stress at elbow extension.
The LCL is weaker than the MCL.
The UCL helps guide motion throughout flexion.

Elbow Joint Stability

The elbow is most stable in full extension (closed-packed position) due to bony contact and ligamentous integrity.
The UCL and RCL prevent valgus and varus stresses, respectively.
The joint capsule's effectiveness in preventing varus and valgus stress changes depending on elbow position.
Co-contraction of flexor and extensor muscles of the wrist and elbow contribute to stability.

Elbow Joint Axis of Motion

The axis of motion is centered in the middle of the trochlea, and is not as fixed as previously thought.

Carrying Angle

The carrying angle (cubitus valgus) is present in anatomical position and is caused by the configuration of the articulating surfaces.
The angle is usually between 10-15° and is greater in females than males.
The carrying angle disappears at 30° of flexion.
The angle is measured from the long axis of the humerus to the long axis of the ulna.

Elbow Joint Mobility Range

The amount of range of motion available depends on the type of motion (active or passive), position of the forearm, body mass index, position of the shoulder, and any swelling present.
Active ROM for flexion is 135°-145° and passive ROM is 150°-160°.
Supination and pronation affect the available flexion.

Muscle Insufficiency

Active insufficiency occurs when a muscle is shortened and can't apply enough force to provide movement.
Passive insufficiency occurs when a muscle can't stretch any further.

Elbow Joint Muscles

The posterior aspect of the elbow joint is comprised of: triceps brachii, anconeus, and supinator.
The anterior aspect of the elbow joint is comprised of: brachialis, biceps brachii, brachioradialis, supinator, pronator teres, flexor carpi radialis, flexor carpi ulnaris, flexor digitorum superficialis, and palmaris longus.

Muscle Force Vectors

Muscle force vectors are drawn to represent the direction of the force the muscle applies and the moment arm at different degrees of elbow flexion (0°, 20°, 90°, 100°).
Muscles whose force vectors are analyzed: brachialis, biceps brachii, brachioradialis, and triceps brachii.

Elbow Joint Muscle Actions

Brachialis functions as a flexor, one-joint muscle, mobility muscle with a large PCSA (physiological cross-sectional area).
The moment arm of the brachialis is greatest at 100° of flexion.
Brachialis is not affected by forearm position and is active during all types of contractions (isometric, concentric, eccentric), and speeds.

Elbow Joint Muscles Actions

Biceps brachii functions as a flexor, two-joint muscle, and mobility muscle.
The long head of the biceps brachii has the largest volume among the flexors.
The biceps brachii has a relatively small PCSA.
The moment arm of the biceps brachii is greatest between 80°-100° of flexion.
The biceps brachii is affected by shoulder position.
Biceps brachii activation changes based on forearm position and magnitude of resistance. It is more active during heavier resistance, and less active with greater pronation at lighter loads.

Elbow Joint: Function and Structure

The elbow is a compound joint acting as a modified hinge.
It is primarily responsible for flexion and extension in the sagittal plane.
There is also slight axial rotation and side-to-side movement of the ulna during flexion and extension.
The open-pack position is between 70-90 degrees of flexion, while the closed-pack position is in full extension.
The elbow joint includes articulation between the humerus, radius, and ulna.
It is stabilized by a single joint capsule, ligaments (medial and lateral), and muscle co-contraction.
The capsule is loose and weak anteriorly and posteriorly but reinforced by ligaments, particularly the medial and lateral collateral ligaments (MCL and LCL).
The MCL is stronger than the LCL, both play a crucial role in preventing excessive valgus and varus stress at different degrees of flexion.
The carrying angle (cubitus valgus) is a natural characteristic, typically 10-15 degrees, resulting from the configuration of the articulating surfaces.
The amount of range of motion is influenced by various factors, including the type of motion (active or passive), position of the forearm, body mass index, shoulder position, and swelling.

Muscles of the Elbow

The elbow joint is comprised of both flexor and extensor muscles.
Flexors: The elbow flexors include the brachialis, biceps brachii, brachioradialis, pronator teres, and flexor carpi radialis.
Extensors: The extensors include the triceps brachii, anconeus, supinator, and extensor carpi radialis longus and brevis.

### Muscle Actions

The brachialis is a one joint muscle (elbow) and the primary flexor.
It has a large physiological cross-sectional area (PCSA) and a moment arm that is greatest at 100 degrees of flexion.
The biceps brachii is a two-joint muscle (elbow and shoulder) and is a strong flexor. Its moment arm is greatest between 80-100 degrees of flexion.
The triceps brachii is a three-headed muscle that extends the elbow. The long head is most active at 0 degrees of shoulder elevation, while the medial head is most active beyond 90 degrees of shoulder elevation.

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Description

This quiz explores the anatomy, functions, and ligaments of the elbow joint. Understand the structure that comprises this vital joint, as well as its role in mobility and stability. Test your knowledge on the articulations and ligaments contributing to elbow mechanics.