The forearm and wrist (Bones)

Question 1

State the joints and muscle information at the proximal end of the forearm

Answer 1

There is a superior radio-ulnar joint that connects the bones. The head of the radius here is substantially smaller compared to the base of the ulna here. The ulna is much more stable here.

At this region, on the lateral aspect, the muscles are responsible for the extension of the elbow and wrist. They also supinate the forearm

At this region, on the medial aspect, the muscles are responsible for the flexion and pronation of the forearm

The annular ligament of the radius is also location here

Question 2

State the joints and muscle information at the distal end of the forearm

Answer 2

There is an inferior radio-ulnar joint that connects the bones. The head of the ulna here is substantially smaller compared to the base of the radius here. The radius is much more stable here.

At this region, on the posterior aspect, there are 12 muscles and they contribute to the extension and supination of the forearm.

At this region, on the anterior aspect, there are 8 muscles and they contribute to the flexion and pronation of the forearm. Even though there are fewer muscles, they have twice the strength

The head of the ulna attaches to the ulnar notch on the radius and the Triangular Fibrous Complex (TFC)/Fribrous Articular disc on the base of the radius attaches to the ulnar styloid process

Question 3

What joint is between the forearm and the carpals?

Answer 3

The wrist joint proper.

Question 4

Details about articulation of wrist and ulna

Answer 4

The ulna does not contribute to the articulation with carpal bones of the wrist

Question 5

What is the interosseous membrane and what are its functions?

Answer 5

The interosseous membrane joins the radius and ulna by its length. It is attached to the medial border of the radius and the lateral border of the ulna. Together with the intermuscular septa, it separates the anterior compartment from the posterior compartment in the forearm

It acts as a hinge, a place for muscle attachment and force transmission (transmit force from radius to more stable ulna at elbow joint)

Question 6

What is the angle of the forearm wrt the arm when is it supinated?

Answer 6

15 degrees. For females, it may be larger due to the larger hips.

Question 7

What are the 3 joints in the hand?

Answer 7

1. Radiocarpal joint (wrist joint proper)
2. Midcarpal joint
3. Carpometacarpal join

Question 8

State the movements at each of the 3 joint regions in the wrist

Answer 8

1. At the radiocarpal joint, there is adduction/abduction, flexion/extension and rotation of the wrist
2. At the midcarpal joint, there is some flexion/extension
3. At the carpometacarpal joint, there is very little movement

Question 9

How are the carpal bones arranged?

Answer 9

They are arranged into two rows of 4

Question 10

What are the 8 carpal bones found within the hand and what are their locations?

Answer 10

Radiocarpal joint

From lateral to medial on the proximal row.

1. Scaphoid (boat-like)
2. Lunate (crescent-shaped)
3. Triquetral (3 sided)
4. Pisiform

Midcarpal joint

From lateral to medial on the distal row.

1. Trapezium
2. Trapezoid
3. Capitate
4. Hamate (has a hook)

Carpometacarpal joint

Way to remember:
(S)ome 
(L)overs
(T)ry
(P)ositions
(T)hat
(T)hey
(C)annot
(H)andle

Question 11

What is the flexor retinaculum and what are its boundaries?

Answer 11

It is a deep fascia. Retinaculum means fascia that has thickened and forms a strap to hold the fingers in place.

It spans the medial half to two-thirds of the wrist (does not extend near the radial edge of the wrist). It is attached to the pisiform and hook of the hamate medially, and the tubercles of the scaphoid and trapezium laterally.

This forms the carpal tunnel where long flexor tendons can be found.

Question 12

What is carpal tunnel syndrome?

Answer 12

It occurs when there is too much pressure on the carpal tunnel.