KNS 332 Exam 2 Review

Ligaments and cartilage both contribute to the dynamic stability of a joint.

• True

• False

Answer explanation

Correct! Neither ligaments or cartilage are contractile tissues which means that they cannot contribute to joint stability in a dynamic way. Instead, they provide static stability to a joint.

Which type of soft tissue connects bone to bone to help guide joint motion?

• Cartilage

• Tendon

• Muscle

• Ligament

Answer explanation

Correct! Ligaments connect bone to bone and help guide joint motion. They also help keep a joint from moving in a way it shouldn’t and provide the central nervous system with information from their proprioceptors.

In what position is the humeroulnar joint when in anatomical position?

• flexion

• extension

• pronation

• supination

Answer explanation

Correct! The humeroulnar (elbow) joint is in extension when in anatomical position. Flexion means the elbow joint is bent. Remember that supination and pronation occur at the proximal radioulnar joint of the forearm.

The humeroulnar joint moves in the sagittal plane about the mediolateral axis, while the proximal radioulnar joint moves in the transverse plane about the superoinferior axis.

• True

• False

Answer explanation

That’s correct!

Which ligament prevents excessive elbow valgus?

• Annular ligament

• Radial collateral ligament

• Ulnar collateral ligament

Answer explanation

Correct! Elbow valgus means the forearm would move laterally away from the midline in the frontal plane. This is not a normal joint motion for the elbow so the UCL prevents this from happening. If the elbow does move into excessive valgus, the UCL is at risk of injury.

Which of the following muscles is an agonist of humeroulnar extension?

• Biceps brachii

• Brachialis

• Brachioradialis

• Triceps brachii

Answer explanation

Correct! Notice how the triceps brachii muscle is the only one of these 4 that is located on the posterior side of the elbow joint. Its location helps explain why it can perform elbow extension.

Which of the following muscles is an agonist of supination? Select all that apply.

• Brachioradialis

• Supinator

• Biceps brachii

• Pronator teres

Answer explanation

Correct! Brachioradialis can cause proximal radioulnar supination from a pronated position up to the neutral forearm position. As its name suggests, the supinator muscle supinates the proximal radioulnar joint. Biceps brachii is also an agonist of supination due to its attachment on the radial tuberosity which also explains why the biceps brachii is most effective as an elbow flexor when the forearm is in supination.

The anconeus muscle is an agonist of humeroulnar extension, but due to its small size acts more like an assistant to triceps brachii.

• True

• False

Answer explanation

Correct! The anconeus is a small muscle located on the posterior side of the elbow joint. So will it will perform elbow extension when it contracts concentrically, it is not as large as the triceps brachii muscle and will act more as an assistant rather than a prime mover.

On what side of the joint are the elbow flexor muscles located?

• Lateral

• Posterior

• Anterior

Answer explanation

Correct! These muscles all have a line of pull that is anterior to the elbow joint’s mediolateral axis of rotation. This explains why these muscles are all agonists of elbow flexion.

Pulled elbow syndrome occurs when the head of the radius is pulled out of the annular ligament and away from its articulation site on the ulna. Which landmark of the ulna should the radial head articulate with?

• Radial notch

• Capitulum

• Trochlea

• Coronoid fossa

Answer explanation

Correct! The rim of the radial head articulates with the radial notch of the ulna to form the proximal radioulnar joint. The annular ligament wraps around the radial head to hold it firmly to the ulna while still allowing the radius to rotate around itself for pronation and supination.