Hand

Musculoskeletal overview

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Figure 1: Transverse section of distal forearm¹

Figure 2: Transverse cut of the Hand¹

Figure 3: Mucous sheaths of the tendons of the wrist and digits¹

Figure 4: Mucous sheaths of the dorsal hand¹

Figure 5: Palmar aponeurosis¹

Figure 6: Muscles of the thumb¹

Palmar muscles of the hand (left)¹

Carpal bones

Figure 7: Bones of the left hand (Anterior surface)¹

Figure 8: Bones of the left hand (posterior surface)¹

• Proximal carpal row:
  • Scaphoid
  • Lunate
  • Triquetrum
• Distal carpal row:
  • Trapezium
  • Trapezoid
  • Capitate
  • Hamate
• Pisiform

Note

The distal row of carpals form a relatively rigid structure, whereas the proximal carpal row is a mobile structure². The proximal carpal row acts a mobile structure between the rigidity of the radius and ulna proximally and the rigid distal carpal row distally².

Scaphoid bone

Figure 9: Scaphoid bone (left)¹

The scaphoid bone Articular surfaces:

• 2 distal convex surfaces to articulate with:
  • The proximal aspect of the trapezium²
  • The medial surface of the trapezoid²
• 1 concave articular facet: to articulate with the capitate

Stabilization

• 1st factor
  • scapho-trapezial ligament
  • Scapho-trapezoidal ligament
  • Scapho-capitate ligament
• 2nd factor
  • Radio-capitate ligament extends from anterior border of the radial styloid process to the anterior aspect of the capitate².
    • This ligament forms a sling along the anterior aspect of the scaphoid
    • As this ligament is tensioned, it translates the inferior aspect of the scaphoid posteriorly².
    • This ligament functionally checks anterior tilting of the scaphoid when it “lies down” during flexion².
• 3rd factor
  • Tendon of FCR runs anterior to the scaphoid as it courses distally to its distal insertion on the 2nd metacarpal².

Scaphoid tilting

• When in flexion the scaphoid lies flat:
  • The scaphoid is jammed between the distal trapezium and trapezoid and the proximal radius².
  • The inferior pole of hte scpahoidslides on the proximal articular surfaces of the trapezoid and trapezium².
  • While this occurs, the anterior ligaments tension and limit excessive anterior movement².
  • Simultaneously, the proximal scaphoid is blocked by the posterior border of the radius².
• When the lateral pillar is stretching
  • The contraction of FCR helps to limit excessive elongation of the pillar².

See scaphoid-lunate couple.

Read more about the scaphoid bone here

Lunate

Figure 10: Lunate bone (left)¹

The lunate bone is asymmetrical due to its thickened anterior aspect and thinner posterior aspect². This asymmetry changes the effective distance between the capitate, lunate, and radius².

• In neutral: the distance between these 3 bones corresponds to the average lunate thickness²
• In extension: The distance is decreased due to the less bulky posterior aspect of the lunate²
• In flexion: The distance increases due to the bulkier anterior aspect of the lunate

• Articulation
  • Concave distal surface of lunate articulates with the convex capitate head²

See scaphoid-lunate couple.

Read more about the lunate bone here

Triquetrum

Figure 11: Triquetrum bone (left)¹

• Articulation
  • Concave distal surface of triquetrum articulates with the concave proximal surface of hamate²

Read more about the triquetrum bone here

Trapezium

Figure 12: Trapezium bone (left)¹

• Articulation
  • Concave proximal surface articulates with the convex, distal surface of the scaphoid².

Read more about the trapezium bone here

Trapezoid

Figure 13: Trapezoid bone (left)¹

• Articulation
  • The proximal concave surface of the trapezium articulates with the convex distal surface of the scaphoid².

Read more about the trapezoid bone here

Capitate

Figure 14: Capitate bone (left)¹

• Articulation
  • The convex capitate articulates with the medial, concave facet of the scaphoid².
  • Concave distal surface of lunate articulates with the convex capitate head².
    • The capitate head forms a central hinge allowing the lunate to:
      • Tilt laterally²
      • Rotate around the long axis²
      • Tilt antero-posteriorly (sagittal plane)²

Read more about the capitate bone here

Hamate

Figure 15: Hamate bone (left)¹

• Articulation
  • The hamate is mostly in contact with the triquetrum: the concave distal surface of triquetrum articulates with the concave proximal surface of hamate²
  • The hamate has a small articulation with the lunate².

Read more about the hamate bone here

Pisiform

Figure 16: Pisiform bone (left)¹

Read more about the pisiform bone here

Midcarpal Joint

Although the midcarpal joint is made up of many bones, it is best to simplify the hand:

• Each row of carpal bones as a single structure
• Divide the midcarpal joint into a lateral and medial part
  • Lateral part: forms a plane joint between the distal trapezium and trapezoid articulating with the scaphoid²
• Medial part forms a condyloid joint consisting of the capitate head and hamate forming a convex aspect that articulates with the concave surface formed by the 3 proximal carpal bones².

Neutral position

In the midcarpal joint’s neutral position, the hand is straight.

In this position, the scaphoid and distal surface of the radius are in contact². The scaphoid and center proximal surface of the trapezium are in contact².

• Ligaments
  • The anterior ligaments of radio-scaphoid are neither stretched or relaxed².
  • Scapho-trapezial ligament are neither stretched or relaxed².

Extension

As the midcarpal joint moves from neutral to extended, the distance reduces and the trapezium moves posteriorly².

• Contact between the articular surfaces of distal radius and the scaphoid².
  • Specifically the contact on the distal radius moves slightly anterior²
  • Contact point on the proximal scaphoid moves slightly posterior²
• Contact between the trapezium and scaphoid².
• Anterior ligaments increase tension²

Flexion

During flexion, the distances between the radius and trapezium also reduces when moving from neutral to flexion².

• Moving into flexion, the scaphoid lies flat and most of its contact is on the posterior aspect of the radius².
• During midcarpal flexion, the trapezium slides proximally and anteriorly on the distal scaphoid².

Scaphoid-lunate couple

The wrist flexion-extension movement divides into 3 sectors:

1. first 20° from neutral: The movements ar small, the ligaments are slack, and intraarticular pressure is minimal².
2. 40° from neutral: the ligaments being to stretch and intraarticular pressure rises
   • Up to this point, the movements involving the wrist and midcarpal joint have roughly the same range².
3. 80° from neutral: Ligament tension and intraarticular pressure reaches a maximum².

Important

Beyond section 3, the ligaments tear and damage. These damages may go undetected. This can lead to instability, fracture, and dislocations².

Note

The concept that as you increase range at the wrist, you increase the restraint or locking mechanism is important². This is an essential concept for understanding how the lunate and scaphoid pillars lock during wrist extension².

Locking scaphoid pillar

Locking lunate pillar

Muscles of the wrist

• Anterior wrist muscles
  • FCR
  • Palmaris longus
  • FCU
• Posterior wrist muscles
  • ECU
  • ECRL
  • ECRB
  • APL
  • EPB
  • EPL
• Groups
  • Group I
  • Group II
  • Group III
  • Group IV

Metacarpal and phalangeal bones

There are 5 metacarpal bones, 1 for each digit.

In terms of size the 1st metacarpal is the shortest and stoutest, the 2nd is the longest, and the length decreases from 3rd-5th metacarpals³.

The metacarpals have distinct osteologic features:

• Base: Proximal end that articulates with the carpals³
• Shaft: Between the base and neck³
• Neck
• Posterior tubercles: Attachment for the collateral ligaments³
• Head: Convex articulation for proximal interphalangeal joint³

1st Metacarpal

Figure 17: 1st metacarpal (left)¹

The “1st metacarpal” is part of the thumb and is the shortest and stoutest³.

Read more about the 1st metacarpal here

2nd Metacarpal

Figure 18: 2nd metacarpal (left)¹

The 2nd metacarpal is generally the longest

Read more about the 2nd metacarpal here

Figure 19: 3rd metacarpal (left)¹

Read more about the 3rd metacarpal here

Figure 20: 4th metacarpal (left)¹

Read more about the 4th metacarpal here

Figure 21: 5th metacarpal (left)¹

Read more about the 5th metacarpal here

Figure 22: Plan of ossification of the hand¹

Proximal phalanx

Osteologic features of the phalanx:

• Base
• Shaft
• Head (Proximal and middle phalanx only)
• Tuberosity (Distal phalanx only)

Rays of the Hand

1st Ray(Thumb)

2nd Ray (Index)

3rd Ray (Middle)

4th Ray (Ring)

5th Ray (Pinky)

Arches

Similar to the arches of the feet, the hand also has palmar concavity known as “arches”³.

There are 3 arches:

1. Proximal transverse arch: Composed of proximal carpals and forms the carpal tunel³
2. Distal transverse arch
3. Longitudinal arch

Proximal Transverse Arch

The proximal transverse arch is composed of the distal row of carpals³. This arch creates space for the carpal tunnel³. The keystone of this arch is the capitate³.

Proximal Transverse Arch

The distal transverse arch is formed using the MCP joints. Unlike the static proximal transverse arch, the distal transverse arch has great mobility, giving it the freedom to grasp a variety of objects³.

Longitudinal Arch

The longitudinal arch runs proximal to distal and follows the 2nd and 3rd rays³. The proximal end of the longitudinal arch connects to the carpals via the CMC joint³.

Overall Function

The 3 arches are mechanically related to one another³.

Examination

Note

See table 18.2 of Dutton for physical findings on the hand⁴

Table 18.6 Hand and Finger Deformities and Their Possible Causes⁴

Hand Deformities and Their Possible Causes⁴

Deformity	Possible Cause
MCP joint flexion	Rupture of extensor tendon just proximal to MCP joint
Hyperextension of MCP joint	Interossei paralysis
Deepening of anterior (palmar) gutter and inability to fully stretch out the palm	Tightness of anterior aponeurosis
Wasting of hypothenar eminence With clawed hand With flexion of 4-5th digits	Ulnar nerve palsy
Wrist drop with increased flexion of the wrist Flexion of the MCP joint Extension of the DIP joint	Radial nerve lesion
Isolated thenar atrophy	Arthritis of CMC joint Median n lesion C8 or T1 lesion
Apehand deformity with wasting of thenar eminence and inability to perform thumb opposition or abduction	Median n. palsy
Z-deformity of the wrist	Rheumatoid arthritis
Atrophy of hand intrinsics	Pancoast tumor
Claw-hand deformity	Loss of <a href=“/The Archive/Anatomy/Nerves/Upper extremity nerves/ulnar_nerve.html#palsy”>ulnar n. motor innervation to the hand resulting in paralysis of interossei and atrophy of hypothenar eminence. This deformity is more severe when lesions are distal to <a href=“/The Archive/Anatomy/Skeletal Muscles/Upper Limb Muscles/Forearm Anterior Compartment/flexor_digitorum_profundus_FDP.html”>FDP muscle
PIP hyperextension and slight flexion of DIP	Rupture or paralysis of FDS
Fixed flexion deformity of MCP and PIP joints, particularly the 4th finger	Dupuytren contracture
Hook-like contracture of the flexor muscles, which is more evident in wrist extension	Volkmann ischemic contracture

Special Tests

Provocation Tests

• Scapholunate Shear Test

Tendon special tests

• The Integrity of the Central Slip (Extensor Hood Rupture): “The patient flexes the finger to 90 degrees at the PIP joint over the edge of the table. The patient is then asked to extend the PIP joint, while the clinician palpates the middle phalanx (Fig. 18-57). The absence of extension force at the PIP joint and fixed extension at the distal joint indicates complete rupture of the central slip. No diagnostic accuracy”⁴

Ligament Special Tests

• Lunotriquetral Shear (Reagan) Test
• Pisotriquetral Shear Test
• Pivot Shift Test of the Midcarpal Joint
• Scaphoid Shift Test for Carpal Instability
• Gamekeeper’s Thumb test (Skier’s Thumb)
• Murphy Sign

Neurovascular Special Teests

• Allen Test
• Tinel Test for CTS
• APB Weakness for CTS

Pathologies

• Gamekeeper’s Thumb (Skier’s Thumb) pathology

References

1.

Gray H. Anatomy of the Human Body. 20th ed. (Lewis WH, ed.). Lea & Febiger; 1918. https://www.bartleby.com/107/

2.

Jones B. B Project Foundations. b Project; 2025.

3.

Neumann DA, Kelly ER, Kiefer CL, Martens K, Grosz CM. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed. Elsevier; 2017.

4.

Dutton M. Dutton’s Orthopaedic Examination, Evaluation, and Intervention. 5th ed. McGraw Hill Education; 2020.