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Questions and Answers
The medial lip projects farther distally than the lateral lip.
The medial lip projects farther distally than the lateral lip.
True
Muscles insert onto the trochlear groove.
Muscles insert onto the trochlear groove.
False
The triceps brachii originates from the anterior aspect of the humerus.
The triceps brachii originates from the anterior aspect of the humerus.
False
The coronoid process is located on the distal end of the ulna.
The coronoid process is located on the distal end of the ulna.
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The olecranon fossa is deep and broad, situated just proximal to the trochlea.
The olecranon fossa is deep and broad, situated just proximal to the trochlea.
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Muscles originating from the lateral epicondyle include the supinator and wrist extensors.
Muscles originating from the lateral epicondyle include the supinator and wrist extensors.
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The radial notch of the ulna is positioned medial to the trochlear notch.
The radial notch of the ulna is positioned medial to the trochlear notch.
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The trochlear groove spirals slightly toward the lateral direction when viewed from posterior to anterior.
The trochlear groove spirals slightly toward the lateral direction when viewed from posterior to anterior.
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The brachialis muscle originates from the anterior aspect of the humerus.
The brachialis muscle originates from the anterior aspect of the humerus.
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The joint capsule is described as large, loose, and weak anteriorly and posteriorly.
The joint capsule is described as large, loose, and weak anteriorly and posteriorly.
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The medial collateral ligament contains two sets of fibers.
The medial collateral ligament contains two sets of fibers.
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The posterior ligament of the elbow runs transversely across the humerus.
The posterior ligament of the elbow runs transversely across the humerus.
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The lateral collateral ligament has only one set of fibers.
The lateral collateral ligament has only one set of fibers.
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The anterior fibers of the medial collateral ligament are considered the weakest.
The anterior fibers of the medial collateral ligament are considered the weakest.
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The capsule blends with the annular ligament except posteriorly.
The capsule blends with the annular ligament except posteriorly.
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Bardinet's ligament is a term used for the posterior set of the lateral collateral ligament.
Bardinet's ligament is a term used for the posterior set of the lateral collateral ligament.
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The annular ligament is strengthened posteriorly by the radial set of the lateral collateral ligament.
The annular ligament is strengthened posteriorly by the radial set of the lateral collateral ligament.
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Cooper's ligament provides reinforcement through transverse fibers.
Cooper's ligament provides reinforcement through transverse fibers.
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The stability of the elbow is primarily influenced by its movements in the sagittal plane.
The stability of the elbow is primarily influenced by its movements in the sagittal plane.
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Passive flexion can reach up to 170° due to the influence of the radial head against the radial fossa.
Passive flexion can reach up to 170° due to the influence of the radial head against the radial fossa.
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The coronoid fossa is responsible for limiting elbow flexion during movement.
The coronoid fossa is responsible for limiting elbow flexion during movement.
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The olecranon fossa is involved in the process of elbow extension.
The olecranon fossa is involved in the process of elbow extension.
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The humerus makes an angle of 60° with the shaft to promote stability in the elbow joint.
The humerus makes an angle of 60° with the shaft to promote stability in the elbow joint.
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During flexion of the elbow, the triceps muscle develops tension actively.
During flexion of the elbow, the triceps muscle develops tension actively.
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The coronoid process obstructs flexion at the elbow joint.
The coronoid process obstructs flexion at the elbow joint.
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The anterior angulation of the distal humerus provides flexibility for elbow extension.
The anterior angulation of the distal humerus provides flexibility for elbow extension.
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An absence of mechanical factors would allow for complete flexion of the elbow.
An absence of mechanical factors would allow for complete flexion of the elbow.
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The articular surface of the ulna is angled 45° posteriorly to the long axis.
The articular surface of the ulna is angled 45° posteriorly to the long axis.
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There is no space available for muscles during full elbow flexion due to contact between the two bones.
There is no space available for muscles during full elbow flexion due to contact between the two bones.
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The biceps generates more elbow flexor torque when the shoulder is flexed.
The biceps generates more elbow flexor torque when the shoulder is flexed.
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Gravity force performs elbow extension when the arm is unloaded in an open kinematic chain.
Gravity force performs elbow extension when the arm is unloaded in an open kinematic chain.
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The brachialis is affected by the position of the shoulder during elbow flexion.
The brachialis is affected by the position of the shoulder during elbow flexion.
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In a closed kinematic chain, the triceps controls elbow flexion concentrically.
In a closed kinematic chain, the triceps controls elbow flexion concentrically.
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The biceps generates its greatest torque at elbow flexion angles between 80 and 100°.
The biceps generates its greatest torque at elbow flexion angles between 80 and 100°.
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A person with C6 tetraplegia can utilize the pectoralis major muscle for elbow extension.
A person with C6 tetraplegia can utilize the pectoralis major muscle for elbow extension.
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The brachioradialis has its peak moment arm unaffected by the elbow angle.
The brachioradialis has its peak moment arm unaffected by the elbow angle.
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The biceps brachii is a one-joint muscle and works independently of the shoulder position.
The biceps brachii is a one-joint muscle and works independently of the shoulder position.
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The biceps muscle is primarily active during eccentric contractions when the forearm is supinated.
The biceps muscle is primarily active during eccentric contractions when the forearm is supinated.
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During isotonic eccentric action, the biceps controls elbow extension when a weight is held.
During isotonic eccentric action, the biceps controls elbow extension when a weight is held.
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The push-pull movements are rooted in the mechanics of the triceps and biceps during lifting tasks.
The push-pull movements are rooted in the mechanics of the triceps and biceps during lifting tasks.
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The biceps muscle becomes less effective as an elbow flexor beyond 100° of flexion.
The biceps muscle becomes less effective as an elbow flexor beyond 100° of flexion.
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The brachioradialis is active during slow, unresisted, concentric elbow flexion.
The brachioradialis is active during slow, unresisted, concentric elbow flexion.
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Eccentric contraction of the triceps is important for controlling elbow flexion during a push-up.
Eccentric contraction of the triceps is important for controlling elbow flexion during a push-up.
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The brachialis is inactive during fast motions involving elbow flexion.
The brachialis is inactive during fast motions involving elbow flexion.
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The position of the shoulder has no effect on the brachioradialis's performance.
The position of the shoulder has no effect on the brachioradialis's performance.
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Study Notes
Distal Humerus
- The medial lip of the distal humerus is prominent and projects farther distally than the lateral lip.
- The trochlear groove is located midway between the medial and lateral lips.
- Muscles originate from the anterior and posterior aspects of the distal humerus.
- Muscles that originate on the shaft: Brachialis, brachioradialis, extensor carpi radialis longus, triceps brachii medial and lateral head
- Muscles that originate on the medial epicondyle: Pronator teres, flexor carpi radialis, palmaris longus, superficial flexor digitorum, and flexor carpi ulnaris
- Muscles that originate on the lateral epicondyle: Supinator, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and anconeus
Distal Ulna
- The ulna has a thick proximal end.
- The concave trochlear notch of the ulna is the large jawlike process located between the anterior tips of the olecranon and coronoid processes.
- The coronoid process projects sharply from the anterior proximal ulna.
- The radial notch of the ulna is an articular depression just lateral to the inferior aspect of the trochlear notch.
Elbow Joint Capsule and Ligaments
- The capsule is large, loose, and weak anteriorly and posteriorly.
- The capsule blends with the proximal border of the annular ligament except posteriorly.
- The capsule is reinforced anteriorly by oblique and vertical bands of fibrous tissue, posteriorly by the posterior ligament, and laterally/medially by the collateral ligaments.
- The medial collateral ligament arises from the medial epicondyle and consists of three sets of fibers: the anterior set, the intermediate set, and the posterior set.
- The lateral collateral ligament arises from the lateral epicondyle and consists of two (or three) sets of fibers: the anterior or radial set, the thicker intermediate or lateral set, and the posterior set.
Elbow Flexion
- Passive flexion is limited by the impact of the radial head against the radial fossa, the coronoid process against the coronoid fossa, the tension in the posterior part of the capsule, and the passive tension developed in the triceps.
Humero-Ulnar Joint
- The distal humerus resembles a bicycle fork, with the axis of the articular surfaces running through the middle portion.
- This midsection contains two fossae: the coronoid fossa (anteriorly) and the olecranon fossa (posteriorly).
- The humeral end angulates anteriorly at 45° with the shaft.
- The articular surface of the ulna is rotated 45° posteriorly to its long axis.
Elbow Flexion and Extension
- Combining active elbow flexion from extension with shoulder extension is an effective way for producing biceps-generated elbow flexor torque.
- In an open kinematic chain, extension of the elbow is performed by gravity when the arm is unloaded, but the biceps controls extension by isotonic eccentric action when weight is held.
- In a closed kinematic chain, the triceps is eccentrically controlled during elbow flexion as the body is lowered to the ground in a push-up and concentrically to extend the elbow.
Clinical Examples of Reverse Concentric Isotonic Contraction
- A person with complete paralysis of the trunk and lower extremity can use near-normal shoulder, elbow flexor, and wrist extensor muscle strength to move up to a sitting position from supine.
- A person with C6 tetraplegia can use the innervated clavicular portion of the pectoralis major and anterior deltoid to pull the humerus toward the midline, rotating the elbow into extension.
Elbow Flexor Muscles
-
Brachialis:
- One-joint muscle
- Works in flexion of the elbow in all positions of the forearm
- Active in all types of contractions
- Active during slow and fast motions
-
Biceps Brachii:
- Two-joint muscle
- Functioning is affected by the position of the shoulder
- Mobility muscle due to its insertion close to the elbow joint axis
- It is less effective in the beginning of the range of motion (ROM) as an elbow flexor rather than a stabilizer
Elbow Flexor Muscle Function
-
Biceps Brachii:
- Has its largest mechanical advantage (MA) between 80° and 100° of elbow flexion.
- Produces its greatest torque in this range.
- Has a small MA when the elbow is in full extension.
- Is active during unresisted elbow flexion with the forearm supinated and when the forearm is midway between supination and pronation in both concentric and eccentric contractions, but it tends not to be active when the forearm is pronated.
- Is active during rapid extension.
-
Brachioradialis:
- It is inserted at a distance from the joint axis, so the largest component of muscle force goes toward joint compression and stability
- Shows no activity during eccentric flexor activity when the motion is slow with the forearm supinated
- Shows no activity during slow, unresisted, concentric elbow flexion
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Description
Explore the anatomy of the distal humerus and ulna in this quiz. Learn about the prominent features of the medial and lateral lips, as well as the muscles that originate from various aspects of these bones. Test your knowledge on the key points related to their structure and function.
