Dr. Meghan A. Phutane discusses the biomechanics of the wrist and hand complex, detailing joint structures and movements. The wrist consists of two joints facilitating flexion/extension and radial/ulnar deviation, while the hand includes 19 bones across its complex of digits. Various ligaments and muscular interactions are essential for stability, motion control, and functional adaptations in gripping and manipulation.

1. Dr. Meghan A. Phutane (PT)
Cardiorespiratory physiotherapist
BIOMECHANICS OF WRIST
&
HAND COMPLEX

2. • The hand consist of 5 digits – 1 thumb & 4 fingers
• There are 8 carpal bones.
• In hand complex there are 19 bones & 19joints, distal to carpal bones.
• Each digit has a carpometacarpal joint (CMC) & a metacarpophalangeal joint
(MCP).
• Each finger has 2 interphalangeal joints one distal (DIP) & one proximal
(PIP) except thumb having only 1 interphalangeal joint.

3. THE WRIST COMPLEX

4. • The wrist (corpus) consist of 2 joints –
• Radiocarpal joint
• Midcarpal joint
RADIOGRAPHIC REPRESENTATION SCHEMATIC REPRESENTATION

5. • The major contribution of wrist complex is to control length tension
relationship in multiarticular hand muscles & to allow fine adjustments of grip.
• Wrist muscles are designed for balance & control rather than maximizing
torque production.
• Wrist complex as a whole is considered biaxial with motions of
flexion/extension (coronal axis) & ulnar deviation / radial deviation (AP axis).
• The ROM of entire complex is variable & reflect differences in carpal
kinematics which could be due to –
• Ligamentous laxity
• The shape of articular surfaces
• The constraining effect of muscles

6. • Normal varying ranges of wrist joint are –
• The 2 joint rather than single joint complex provides –
• Large ROM with less exposed articular surfaces & tighter joint capsule
• Less tendency for structural pinch at extreme ranges
• Flattened multijoint surfaces that are more capable of withstanding
imposed pressures
Flexion 65° - 85°
Extension 60° - 85°
Radial deviation 15° - 21°
Ulnar deviation 20° - 45°

7. RADIOCARPAL JOINT STRUCTURE
• Formed by radius & radioulnar discs as a part of triangular fibrocartilage
complex (TFCC) proximally & scaphoid, lunate & triquetrum distally.

8. PROXIMAL & DISTAL SEGMENTS OF RC JOINT
• Distal radius has single continuous biconcave curvature that is long &
shallow side to side & sharper & shorter anteroposteriorly.
• Proximal joint surface consist of –
1. Lateral radial facet (scaphoid)
2. Medial radial facet (lunate)
3. TFCC (triquetrum & little with lunate in neutral position)
• Proximal radiocarpal joint surface is oblique & angled slightly volarly &
ulnarly.
• Average inclination of radius is 23° & tilted 11° volarly.

10. TFCC –
• Consist of radioulnar disc & various fibrous attachments providing
support to distal radioulnar joint.
• The disc is connected medially via 2 dense, fibrous connective tissue
laminae. Upper laminae include dorsal & volar radioulnar ligament
whereas lower laminae has connections to sheath of ECU tendon,
triquetrum, hamate & base of 5th metacarpal through ulnar collateral
ligament.
• Meniscus homolog – region of irregular connective tissue (part o lower
laminae) traverse volarly & ulnarly from dorsal radius to insert on the
triquetrum.
• Overall TFCC functions at wrist as an extension of distal radius.

12. • Scaphoid, lunate & triquetrum – proximal carpal row.
• Bones are interconnected by 2 ligaments ie. Scapholunate
interosseous & lunotriquetral interosseous ligaments.
• Proximal carpal row & ligaments together appears as a single
biconvex cartilage covered joint surface that can change shape to
accommodate to the demands of space between forearm & hand.
• In radiocarpal joint distal surface is sharper than proximal both in
coronal & sagittal plane – makes joint incongruent.
• This causes greater range of flexion than extension & greater ulnar
deviation than radial deviation.

13. • As the curvature & inclination of the radiocarpal surfaces affects
function, the length of ulna in relation to radius also affects it.
• Ulnar negative variance – shorter ulna than radius at the distal end.
• Ulnar positive variance – longer distal ulna than distal radius.
• Positive variance is associated with changes in TFCC thickness –
potential for impingement of TFCC between ulna & triquetrum.
• Relatively longer ulna is present after distal radius fracture healed in
shortened position – pain at end range of pronation ulnar deviation.
• Negative variance – abnormal force distribution at radiocarpal joint –
potential degeneration – avascular necrosis of lunate (kienbock’s
disease).

14. RADIOCARPAL CAPSULE & LIGAMENTS
• Has strong but somewhat loose capsule & reinforced by capsular &
intracapsular ligaments.
• Most ligaments & muscles crossing radiocarpal joint also contributes
to midcarpal joint stability

15. MIDCARPAL JOINT STRUCTURE
• Articulation between scaphoid, lunate & triquetrum proximally &
trapezium, trapezoid, capitate & hamate distally.
• Functional unit rather than an anatomical unit.
• Has separate fibrous capsule & synovial lining that is continuous with
each intercarpal articulation & some with CMC joint.
• Complex as it has overall reciprocally concave convex configuration.
• Functionally distal carpal row moves as a fixed unit.
• Union of distal carpals also results in equal distribution of loads across
scaphoid-trapezium-trapezoid, scaphoid-capitate, lunate-capitate &
triquetrum-hamate articulations.

16. • Distal row contributes to 2 degrees of freedom to wrist complex with
varying amounts of ulnar/radial deviation & flexion/extension.
• Distal carpal row lads to the foundation of transverse & longitudinal
arches of hand.

17. LIGAMENTS OF THE WRIST COMPLEX
• The ligamentous structure of carpus is responsible for articular
stability as well as guiding & checking motions between & among the
carpals.
• In general, dorsal ligaments are thin & numerous volar ligaments are
thicker & stronger.
•
Ligaments
Extrinsic
Connects carpals to radius ulna proximally or
metacarpals distally
Intrinsic
Interconnects the carpals

18. PROPERTIES EXTRINSIC LIGAMENTS INTRINSIC LIGAMENTS
CONNECTION Carpals to radius ulna
proximally & metacarpals
distally
Interconnect carpals
(intercarpals / inrterosseous)
Stronger & less stiff
Lie within synovial lining
Nutrition Contiguous vascularized
tissue
Through synovial fluid
Risk of injury High Low
Healing Fast Slow
Accept forces first

19. VOLAR CARPAL LIGAMENTS
• Organized into 2 groups : radiocarpal & ulnocarpal ligaments –
composite volar radiocarpal ligaments.
• Has 3 distinct bands – the radioscaphocapitate (radiocapitate); short &
long radiolunate & radioscapholunate ligaments.
• Radioscapholunate – stabilizes scaphoid – disruption causes scaphoid
instability. - ???
• Radial collateral ligament – extension of volar radiocarpal ligaments &
capsule.
• Ulnocarpal ligament complex – composed of TFCC including articular
disc & meniscus homolog; ulnolunate ligament & ulnar collateral
ligament.

20. • 2 Volar intrinsic ligaments – important in wrist function.
• Scapholunate interosseous ligament – maintains scaphoid stability &
so wrist stability.
• Lunotriquetral interosseous ligament – maintains stability between
lunate & triquetrum
• Stretched while wrist extension.

21. DORSAL CARPAL LIGAMENTS
• Dorsal radiocarpal ligament
• Dorsal intercarpal ligament
• Together forms a horizontal ‘V’ that contributes to radiocarpal stability;
notably stabilizes scaphoid during wrist ROM.
• Taut with wrist flexion.

24. FUNCTIONS OF WRIST COMPLEX
Movements of radiocarpal & midcarpal joints :-
• Proximal carpals acts as mechanical link between radius & distal
carpals & metacarpals to which the muscular forces are directly
applied – intercalated segment.

25. Flexion / extension of the wrist –
• In 3 proximal carpal bones, scaphoid has greatest motion & lunate
moves least.
• The movements of complex from complete flexion to extension are –
distal carpal row moves on proximal carpal row → scaphoid & distal
carpals moves on lunate & triquetrum → carpals as a unit move over
radius & TFCC.
• Extension to flexion – reverse process.

26. Radial / ulnar deviation –
• In radial deviation, carpals slide ulnarly over radius with simultaneous
flexion of proximal carpals & extension of distal carpals. The opposite
occurs in ulnar deviation.
• in full radial deviation, both the radiocarpal & midcarpal joints are in
closed packed position.
• Ranges vary according to the wrist position – more to less – neutral
→ fully flexed → fully extended.

27. MUSCLES OF WRIST COMPLEX
Primary role –
• To provide a stable base for hand while permitting positional
adjustments & allow for optimal length tension relationships.
Muscles
Volar (cause flexion)
PL,FCR,FCU
FDS,FDP,FPL
Dorsal (cause extension)
ECRL, ECRB,ECU
EDC,EIP,EDM,EPL,EPB,APL

28. THE HAND COMPLEX

29. • Hand complex consist of 5 digits – 4 fingers & one thumb.
• Each finger has 1 CMC, 1 MCP & 2 IP (proximal & distal) joints
whereas thumb has 1 CMC, 1 MCP & ONLY 1 IP joint.
• Overall there are 19 bones & 19 joints distal to the carpals.

30. CARPOMETACARPAL JOINTS OF FINGERS
• Articulation between distal carpal row with 2nd to 5th bases of
metacarpals (MC).
• The 2nd MC articulates primarily with trapezoid & secondarily
with trapezium & capitate; 3rd MC with capitate; 4th with capitate
& hamate & 5th MC articulates with only hamate.
• Supported by strong transverse & weaker longitudinal
ligaments.
• Deep transverse metacarpal ligament covers 2nd to 4th MC
volarly – tethers together the MC heads & prevents excessive
abduction which contributes to CMC stability.

31. • Proximal transverse (carpal) arch – affects CMC & hand function
but not the wrist function.
• It is formed by trapezium, trapezoid, capitate & hamate (distal
carpal row) – which is concave volarly.
• This concavity is maintained by transverse carpal ligament &
intercarpal ligament. This forms carpal tunnel which contains
median nerve & 9 extrinsic flexor tendons.

33. CMC JOINT RANGE OF MOTION
• In the articulating surface more range is available at MC heads.
The mobility increases from radial to ulnar side of hand.
• 2nd to 4th CMC joints are plane synovial joints having only 1° of
freedom (flexion/extension) whereas 5th CMC joint is saddle joint
with 2° of freedom. (flexion/extension, abduction/adduction &
limited opposition)
• 2nd & 3rd CMC joints – essentially immobile – considered to
have 0° of freedom – as it provides fixed & stable axis for 1st, 4th
& 5th MC heads.

34. PALMAR ARCHES
• The function of fingers CMC joints & their segment is to
contribute to palmar arch system.
• Proximal transverse arch – concavity formed by carpal bones.
• Distal transverse arch – formed by 1st, 4th & 5th MC heads & is
relatively mobile.
• Longitudinal arch – traverse length of the digits from proximal
to distal.
• Deep transverse MC ligament contributes to stability of mobile
arches during grip functions.

35. PALMAR ARCHES

36. • Allows the palm & digits to conform optimally to the shape of the
object being held – allowing maximum surface contact, enhance
stability & increase sensory feedback.
• Muscles crossing CMC joint contributes to palmar cupping –
hollowing of palm accompanies finger flexion & relative
flattening of palm accompanies finger extension.

37. METACARPOPHALANGEAL JOINTS OF FINGERS
• Convex metacarpal head proximally & concave base of 1st
phalanx distally.
• Condyloid joint with 2° of freedom (flexion/extension &
abduction/adduction)
• In sagittal plane, MC head has 180° of articular surface
(predominant portion lying volarly), opposed to 20° of articular
surface on 1st phalanx.
• In frontal plane there is less but more congruent frontal plane.

38. • Surrounded by a capsule – lax in extension – allows some
passive axial rotation of phalanx.
• Collateral ligament at the volarly located deep transverse MC
ligament – enhances joint stability.
• Volar plates – accessory joint structure to enhance joint stability.

39. VOLAR PLATES
• Also called as palmar plates
• Increases joint congruence; provides stability to MCP joints
(limits hyperextension) – so provides indirect support to the
longitudinal arch.
• Composed of fibrocartilage & is firmly attached to base of
proximal phalanx.
• Becomes membranous proximally to blend with volar capsule at
MC heads.
• During MCP extension, the plate adds up the amount of surface
in contact with large MC heads.

40. • Fibrocrtilage composition resist both tensile stresses (MCP
hyperextension) & compressive forces (to protect MC heads
from objects held in palm)
• During flexion – glides proximally – prevents pinching of long
flexor tendons in MCP joint.
• Also blends with & are interconnected superficially by deep
transverse MC ligament.
• sagittal bands (dorsal to deep transverse MC ligaments) –
stabilizes volar plates.

42. COLLATERAL LIGAMENT
• The radial & ulnar collateral ligaments of MCP joints are
composed of 2 parts: collateral ligament proper (cordlike) &
accessory collateral ligament.
• Tension in collateral ligament at full MCP joint flexion (closed
pack position) – limits MCP abduction in full flexion.
• Provides stability throughout the MCP joint ROM

43. RANGE OF MOTION
• ROM at each joint varies; flexion/extension increases radially to
ulnarly with index finger (90°) & little finger (110°).
• Hyperextension – consistent between fingers but varies among
individuals.
• Range of passive hyperextension is used to assess flexibility.
• Abduction/adduction is maximal in MCP extension & restricted
in flexion.

44. INTERPHALANGEAL JOINTS OF FINGERS
• Each proximal & distal IP joints is composed of head of the
phalanx & the base of the phalanx distal to it.
• True synovial hinge joint with 1° of freedom (flexion/extension),
a joint capsule, a volar plate & 2 collateral ligaments.
• Structure similar to MCP joint but with little posterior articular
surface (permits hyperextension)
• Volar plates – reinforce each IP joint capsule, enhances stability
& limits hyperextension. Similar to MCP joint plates except no
connection with deep transverse ligament.

45. • Collateral ligaments – cord like, similar to MCP joint, provides
stability. Injuries to proximal IP joint collateral ligament are
common in sports & at workplace (radial > ulnar collateral)
• Flexion/extension of IP joints of index finger – proximal (100°-
110°) > distal (80°).
• Range of PIP & DIP joint flexion increases ulnarly with 5th PIP &
DIP having flexion ranges of 135° & 90° respectively.
• Additional range to ulnarly fingers – favors angulation of fingers
towards scaphoid & opposition with thumb.

46. EXTRINSIC FINGER FLEXORS
• Muscles of fingers & thumb having proximal attachment above
wrist.
• 2 muscles contributing to finger flexion – flexor digitorum
superficialis (FDS) & flexor digitorum profundus (FDP).
• FDS –
• Flexes proximal IP joint & MCP joint.
• Produces more torque than FDP.
• Crosses fewer joints & superficial to FDP at MCP joint.
• Greater moment arm for MCP joint.
• FDP – Flexes MCP, PIP, DIP joints – more active.

47. • During finger flexion with wrist flexion – FDS & FDP works
together.
• At the proximal phalanx (proximal to PIP), FDP emerges through
split in FDS (camper’s chiasma) & FDS attaches to base of
middle phalanx.
• Both FDS & FDP are dependent on wrist position for optimal
length tension relationship.
• Counterbalancing extensor torque at wrist is provided by
extensor carpi radialis brevis (ECRB) or sometimes by extensor
digitorum communis (EDC).

48. MECHANISM OF FINGER FLEXION
• Optimal function of FDS & FDP depends on –
• Stabilization by wrist musculature
• Intact flexor gliding mechanism
• Gliding mechanism consist of –
• Flexor retinacula
• Bursae
• Digital tendon sheaths

49. • The fibrous retinacular structures (proximal flexor retinacula,
transverse carpal ligament, & extensor retinaculum) tethers the
long flexor tendons to hand – prevents bowstringing of tendons.
• Bursae & tendon sheaths facilitate friction free excursion of
tendons on retinacula.
• FDS & FDP tendons – crosses wrist – pass beneath proximal
flexor retinaculum – through carpal tunnel – ulnar bursa (all 8
tendons).
• Flexor pollicis longus (FPL) – pass through carpal tunnel with
FDS & FDP – then radial bursa encases it.

50. • FDS & FDP tendons of each finger pass through a fibroosseous
tunnel which comprises 5 transversely oriented annular pulleys
(vaginal ligaments) & 3 obliquely oriented cruciate pulleys.
• Annular pulleys –
• A1 – at head of MC
• A2 – volar midshaft of proximal phalanx
• A3 – distal most part of proximal phalanx
• A4 – centrally on the middle phalanx
• A5 – base of the distal phalanx

51. • The base of each pulley is longer than the roof superficially &
roof has slight concavity volarly.
• This prevents the pulleys from pinching each other at extremes
of flexion & minimizes the pressure on the tendon when it is
under tension.

53. • The cruciate pulleys –
• C1 – between A2 & A3
• C2 – between A3 & A4
• C3 – between A4 & A5
• A4, A5 & C3 contains only FDP tendon & no FDS.
• Thumb has different pulley system.
• Function of annular pulleys –
• To keep the flexor tendons close to the bone
• To allow only a minimum amount of bowstringing & migration
volarly from the joint axes.
• Enhances tendon excursion efficiency & work efficiency of long
tendons

54. EXTRINSIC FINGER EXTENSORS
• Extrinsic finger extensors are extensor digitorum communis
(EDC), extensor indicis proprius (EIP) & extensor digiti minimi
(EDM).
• Passes from forearm – beneath extensor retinaculum that
maintains proximity of tendons to the joints & improves
excursion efficiency.
• At MCP joint level EDC tendon of each finger merges with broad
aponeurosis known as dorsal hood or extensor hood.
• EIP & EDM tendons inserts into EDC tendon of index & little
finger at or just proximal to extensor hood.

55. • I

56. • EDC, EIP & EDM – extension of MCP joints of fingers via
connection to extensor hood & sagittal band; also causes wrist
extension.
• Distal to the extensor hood, tendon splits into 3 bands, as –
• Central tendon (inserts on base of middle halanx)
• 2 lateral bands – rejoins as terminal tendon (inserts into
base of distal phalanx)

58. EXTENSOR MECHANISM
• Formed by EDC, EIP, EDM, extensor hood, central tendon, &
the lateral bands that merge into terminal tendon.
• Passive components are –triangular ligaments (helps stabilize
the bands on the dorsum of fingers) & sagittal bands (connects
volar surface of hood to volar plates & deep transverse MC
ligament – prevents bowstringing of extensor tendons).
• The dorsal interossei (DI), volar interossei (VI) & lumbrical
(intrinsic musculature) are active components of extensor
mechanism.
• Passive element – oblique retinacular ligament (ORL)

59. INTRINSIC FINGER MUSCULATURE
• With all attachments distal to radiocarpal joint.
Dorsal & volar interossei muscles :-
• Arise between the MC & are important part of extensor
mechanism.
• 4 DI & 3-4 VI muscles
• DI & VI are alike in their locations & some of their actions;
characterized by their ability to produce MCP joint abduction &
adduction respectively.

60. • The interossei muscle fibers join extensor expansion in 2
locations; some fibers attach proximally to the proximal phalanx
& to extensor hood; some attach more distally to lateral bands &
central tendons.
• 1st DI has most consistent attachment - into bony base of
proximal phalanx & extensor hood.
• 2nd & 3rd DI have both proximal & distal attachments.
• 4th DI – not actually present – abductor digiti minimi (ADM) plays
that role

61. • 3 VI muscles – have distal attachment only (lateral band /
central tendon).
• Proximal interossei have predominant effect on MCP joint only,
but distal interossei will produce their predominant action at IP
joints & some effect on MCP joints.
• All DI & VI muscles pass dorsal to transverse MC ligament but
volar to axis of MCP joints flexion/extension.

62. Role of interossei at MCP joint in Extension :-
• Effective stabilizers & prevent clawing due to flexion torque.
• Balances passive tension in the extrinsic extensors at MCP joint
at rest.
• Interossei muscles are effective abductors & adductors at MCP
joint when MCP joint is in extension.
• Proximal insertion muscles are more effective than distal
insertion muscles. So abduction is stronger than adduction.

63. Role of interossei at MCP joint in flexion :-
• From extension to flexion – tendons & action lines of interossei
muscles migrate volarly away from coronal axis of MCP joint –
increases moment arm for MCP flexion – action line being
nearly perpendicular to moving segment.
• Increases the flexion torque at MCP joint as it approaches to full
flexion.
• The volar migration of interossei is restricted by deep transverse
MC ligament – prevents loss of active tension & serves as
anatomical pulley.
• In full MCP flexion, abduction/adduction is restricted due to –
tight collateral ligaments, shape of condyles on MC heads &
active insufficiency of fully shortened interossei muscles.

64. Role of interossei at IP joint in IP extension:-
• Ability to cause IP extension is influenced by its attachments.
• IP joint extension produced by distal interossei is stronger than
MCP abduction/adduction during MCP extension.
• Index & little finger has weaker IP extension than middle & ring
fingers (fewer distal interossei muscles).
• Overall, proximal components are effective in MCP flexion &
distal component in IP extension. So most consistent activity of
interossei is when MCP joints are flexed & IP joints are
extended – advantage of optimal biomechanics for both DI & VI.

66. Lumbrical muscles:-
• Only muscles in the body that attaches to tendons of other
muscles.
• Each muscle originates from tendon of FDP muscle in the palm
– volar to deep transverse MC ligament – attaches to lateral
band of extensor mechanism on radial side.
• Crosses MCP joint volarly & IP joints dorsally.
• Difference in interossei & lumbricals is – more distal insertion of
lumbricals, origin at FDP & great contractile range of lumbricals.

67. • Effective IP extensors than MCP joint position.
• Deep transverse MC ligament prevents lumbricals migration
dorsally & loosing tension as MCP & IP extends.
• Lumbrical contraction increases tension in lateral band & FDP
tendon too.
• Acts as both agonist & synergist for IP extension.
• As lumbricals activate to cause IP extension, there is effective
release of passive tension in FDP tendon.
• Also assist FDP indirectly during hand closure.
• Functionally MCP joint flexion is weaker in lumbricals than
interossei.
• Large range of lumbricals, prevents active insufficiency when
shortening over MCP & IP joints.

69. THE THUMB

70. • Carpometacarpal (CMC) or
trapeziometacarpal (TM) joint
– between trapezium & base
of 1st metacarpal head.
• Saddle joint with 2° of
freedom – flexion/extension,
abduction/adduction ; permits
some axial rotation – net
effect being circumduction
called “opposition” – permits
tip of thumb to oppose tips of
fingers.

71. CARPOMETACARPAL JOINT OF THUMB
• Saddle shaped portion of trapezium is concave in sagittal plane
(abduction/adduction) & convex in frontal plane
(flexion/extension).
• Spherical portion on trapezium – convex in all directions.
• Base of 1st MC has reciprocal shape to the trapezium.
• Flexion/extension & abduction/adduction occurs on saddle
surface but axial rotation at spherical surface.
MOVEMENT PLANE AXIS
Flexion/extension Sagittal Oblique AP axis
Abduction/adduction Frontal Oblique coronal axis

72. • Capsule of 1st CMC joint is relatively lax but is reinforced by radial,
ulnar, volar & dorsal ligaments.
• Intermetacarpal ligament – helps to tether the base of 1st & 2nd MC,
prevents extremes of radial & dorsal displacement of base of 1st MC
joint.
• Dorsoradial & anterior oblique ligaments – key stabilizers of CMC
joint.
• OA changes with aging are common at 1st CMC joint, may be due to
cartilage thinning in high load areas imposed on this joint by pinch &
grasps across incongruent surfaces.
• Closed pack position – extremes of both abduction & adduction

73. • Unique range & direction of motion.
• Opposition is sequential abduction, flexion & adduction of 1st
MC with simultaneous rotation.
• The functional significance of 1st CMC joint is appreciated in all
forms of prehension.

74. MCP & IP JOINTS OF THUMB
MCP joint :-
• Between head of 1st MC & base of proximal phalanx.
• Condyloid joint with 2° of freedom – flexion/extension &
abduction/adduction.
• The joint capsule, volar plates & collateral ligaments are similar
to other MCP joints.
• Function – to provide additional flexion range to thumb in
opposition & to allow thumb to grasp & contour to objects.
• Though structure is same flexion/extension ranges are half of
the other fingers. Abduction/adduction is extremely limited.

75. IP joints :-
• Between head of proximal phalanx & base of distal phalanx.
• Similar to other IP joints of the fngers.

76. MUSCULATURE
Extrinsic thumb muscles :-
• The 4 extrinsic thumb muscles are -
• Flexor pollicis longus (FPL)
• Extensor pollicis longus (EPL)
• Extensor pollicis brevis (EPB)
• Abductor pollicis longus (APL)

77. FPL –
• Inserts on distal phalanx
• Correlates to FDP
• At wrist, invested by radial bursa which is continuous with its
digital tendon sheath.
• Unique; Functions independently; only muscle responsible for
thumb flexion at IP joint.
• Sits between the sesamoid bones – derives some protection
from the bones.

78. • Other 3 muscles are located dorsoradially.
• EPB & APL – common course – dorsal forearm – 1st dorsal
compartment-radial aspect of wrist.
• ABL inserts on base of MC joint. EPB inserts on base of proximal
phalanx - abducts CMC joint , slight radial deviation of wrist.
• EBP-extension of MC joint
• EPL-inserts on base on base of distal phalanx- at proximal phalanx
EPL is joined by expansion from APB, 1st volar interossei & adductor
pollicis (ADP)-extends thumbs IP joint to neutral but no
hyperextension, extends and adducts 1st CMC joint

79. Intrinsic thumb muscles :-
• 5 thenars muscles – originates from carpal bones and flexor
retinaculum.
• Opponens pollicis(OP)- only intrinsic muscle having distal
attachment on 1st MC on the lateral side – very effective in
positioning the MC in an abducted ,flexed and rotated posture
• APB , FPB , AdP &1st volar interossei inserts on proximal
phalanx.
• FPB has two heads of insertion.
• Large lat. Head attaches to ABL-abduction.
• Medial head attaches to AdP-adduction

80. • 1ST dorsal interossei- though not consider as a thenar muscle
contributes to thumb function-CMC joint distraction, assist
thumb adduction.
• Thenar muscles- active in most grasping activities
• Activity of extrinsic thumb muscle in grasp is partially function
of helping to position the MCP and IP joints , main function
being returning the thumb to extension from its position

81. PREHENSION

82. • Prehension activities involves grasping or taking hold of an
object between any 2 surfaces of hand. Thumb paticipate in
most but not all the prehension activities.
Prehension
Power grip
(full hand
prehension)
Precision handling
(finger thumb
prehension)

83. POWER GRIP PRECISION
Forceful act resulting in flexion of all
finger joints. The thumb acts as a
stabilizer to the object held in fingers or
palm.
Skillful placement of an object
between fingers or between finger &
thumb. No involvement of palm.
Phases • Opening of hand
• Positioning the fingers
• Bringing the fingers to the object
• Maintaining the static phase
• Opening of hand
• Positioning the fingers
• Bringing the fingers to the object
Object is grasped to move through
space by some proximal joints
Fingers & thumb grasps the object
to manipulate it within the hand
Thumb is generally adducted. Thumb is generally abducted.

85. POWER GRIP
• Fingers function to clamp on or hold an object into the palm.
• Fingers sustain flexion position that varies in degree with size, shape
& weight of the object; palmar arches around it.
• Thumb – serves as additional surface to finger palm by adducting
against the object.
• Different power grips –
• Cylindrical grip
• Spherical grip
• Hook grip
• Lateral prehension

86. • Involves use of all finger flexors
• FDP works predominantly
• Interossei muscles – primary MCP
flexors, abductors/adductors
• FPL & thenar muscles- flexion &
adduction of thumb.
• Hypothenar eminence-flex & abduct
MCP joint.
• Typically with wrist in neutral /
extension & slight ulnar deviation.
• E.g. turning a door knob.
CYLINDRICAL GRIP

87. • Most respect to cylindrical
grip but greater spread of
fingers to encompass the
object.
• More activity of interosseus
for e.g. holding a ball.
SPHERICAL GRIP

88. • Specialised form of
prehension- function
primarily of fingers.
• Major activity of FDP
&FDS.
• Load – more distally FDP,
proximally (FDS)
• Thumb- moderate to full
extension.
• E.g. - carrying a briefcase.
HOOK GRIP

89. • Contact between two
fingers.
• MCP & IP joint- in
extension as contigious
MCP joint simultaneously
abduct & adduct
• Extensor musculature pre
dominates.
• E.g. holding a paper
LATERAL PREHENSION

90. PRECISION HANDLING
• Require much finer motor control & more dependent on intact
sensation.
• In “two – jaw chuck”,one jaw is thumb( abducted & rotated) & 2nd
jaw is by distal tip, the pad or the side of finger.
• 3 varieties of prcesion are –
• Pad to pad prehension
• Tip to tip prehension
• Pad to side prehension.

91. • Involves opposition of pad or pulp
of thumb to pad or pulp of finger.
• The pad has greatest
concentration of tactile corpuscles.
• MCP & proximal IP joint of the
finger – partially flexed
• Distal IP joint- extended or slightly
flexed.
• Thumb- CMC flexion, abduction &
rotation; MCP & IP joint partially
flexed or extended.
• E.g. holding a foreceps
PAD TO PAD PREHENSION

92. • Muscle activity almost
same to pad to pad
prehension with some key
differences like IP joint of
the fingers & the thumb
have range & force to
create full flexion.
• MCP joint of opposing
finger deviates ulnarly.
• E.g. holding a pen.
TIP TO TIP PREHENSION

93. • Key grip or lateral pinch.
• Between thumb & side of
index finger
• Thumb-more adducted &
less rotated least precise
form of precesion handling.
SIDE TO SIDE PREHENSION

94. FUNCTIONAL POSITION OF WRIST & HAND
• The functional position is –
• Wrist complex in slight extension (20°) & slight ulnar
deviation (10°)
• Fingers moderately flexed at MCP joint (45°) & proximal ip
joint (30°) & slightly flexed at distal IP joint