Anatomical Kinesiology Notes

4 of the 5 muscles have origins on the medial epicondyle of the humerus, forming the common flexor tendon.
All 5 muscles are located on the anterior and medial (ulnar) aspect of the forearm, with attachments on the anterior (volar, palmar) side of the wrist and/or hand bones.
While these muscles cross the elbow joint, their concentric action of flexion is predominantly synergistic.

Extrinsic Wrist Flexors:
- 3 of the 5 muscles insert on the carpals or metacarpals, but do not cross the metacarpophalangeal joints (i.e., they have primary concentric actions at the wrist only).
- The origins of extrinsic muscles are external (radius, ulna, or humerus).
Intrinsic Hand Muscles:
- Have origins that are internal (within) the wrist and hand.
- Extrinsic muscles are grouped by function and location.

Origin: Medial epicondyle of the humerus
Insertion: Base of 2nd & 3rd metacarpals (palmar [volar] surface)
Primary Concentric Actions:
- Sagittal Plane: Wrist flexion
- Frontal Plane: Wrist radial deviation (abduction)

Flexor: Indicates a primary concentric action (flexion)
Carpi: Indicates the muscle does not cross the metacarpophalangeal joint, thus only acts at the wrist
Radialis: Indicates the side of the hand where the tendon of the muscle inserts, useful for determining radial or ulnar deviation

Superficial muscle located medial to the pronator teres, and is the most lateral of the wrist flexors

The origins of all wrist flexors are on the anterior medial (ulnar) surface of the forearm, with attachments on the palmar side of the hand.
Synergist Concentric Actions (Note: Will not be tested): Elbow flexion.

Origin: Medial epicondyle of the humerus
Insertion: Palmar aponeurosis
Primary Concentric Actions:
- Sagittal Plane: Wrist flexion
The Name:
- Palmaris: Indicates the attachment into the palmar aponeurosis
- Longus: Distinguishing characteristic of the palmaris longus is its LONG tendon, as there is also a brevis within the hand
Location:
- Superficial muscle located medial to the flexor carpi radialis
- Absent in about 20% of the population
Insertion Details:
- Palmar aponeurosis (could also identify flexor retinaculum)
- Aponeurosis is a sheet of white fibrous tissue that is an extension of a tendon with a wide area of attachment
Primary Concentric Actions: Wrist flexion
Synergist Concentric Actions (Note: Will not be tested): Elbow flexion

Origin: Medial epicondyle of the humerus
Insertion: Sides of base of middle phalanx of 2nd – 5th fingers
Primary Concentric Actions:
- Sagittal Plane: Wrist flexion
- 2nd – 5th MCP flexion
- 2nd – 5th PIP flexion
The Name:
- Flexor: Indicates a primary concentric action
- Digitorum: Indicates the muscle also has a function in the hand (with the digits), the insertion will be in the hand
- Superficialis: Indicates the muscle is superficial with respect to the flexor digitorum profundus
Location:
- The proximal portion of the muscle is medial to the palmaris longus
- Much of the muscle is deep to the palmaris longus and the flexor carpi radialis
Insertion Details:
- The tendon splits distally into 4 tendons. Each tendon then splits again to insert into the sides of the base of middle phalanx of the 2nd – 5th fingers
Primary Concentric Actions: Wrist flexion, 2nd – 5th finger MCP flexion, 2nd – 5th finger PIP flexion
Synergist Concentric Actions (Note: Will not be tested): Elbow flexion

Origin: Proximal 3/4 anterior medial ulna
Insertion: Sides of base of distal phalanx of 2nd – 5th fingers
Primary Concentric Actions:
- Sagittal Plane: Wrist flexion
- 2nd – 5th MCP flexion
- 2nd – 5th PIP flexion
- 2nd – 5th DIP flexion

Flexor: Indicates a primary concentric action (flexion)
Digitorum: Indicates the muscle also has a function in the hand (with the digits), thus the insertion will be in the hand
Profundus: Indicates the muscle is deep relative to the flexor digitorum superficialis.
- The only one of the wrist flexors that does not originate on the medial epicondyle.
- Its function is significant as it flexes all the joints in the wrist and hand!

The muscle is deep to the flexor digitorum superficialis and other wrist flexors.
Origin: Proximal ¾ of the anterior (volar) and medial surface of the ulna.
Insertion: The tendon splits into 4 tendons, which split again to insert into sides of the base of distal phalanx of the 2nd – 5th fingers. Notice the difference compared to the flexor digitorum superficialis.