Dr. Meghan A. Phutane (PT)
BIOMECHANICS OF WRIST
• 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
• Each finger has 2 interphalangeal joints one distal (DIP) & one proximal
(PIP) except thumb having only 1 interphalangeal joint.
• The wrist (corpus) consist of 2 joints –
• Radiocarpal joint
• Midcarpal joint
RADIOGRAPHIC REPRESENTATION SCHEMATIC REPRESENTATION
• 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
• 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
• 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
Flexion 65° - 85°
Extension 60° - 85°
Radial deviation 15° - 21°
Ulnar deviation 20° - 45°
RADIOCARPAL JOINT STRUCTURE
• Formed by radius & radioulnar discs as a part of triangular fibrocartilage
complex (TFCC) proximally & scaphoid, lunate & triquetrum distally.
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 &
• Average inclination of radius is 23° & tilted 11° volarly.
• 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
• Meniscus homolog – region of irregular connective tissue (part o lower
laminae) traverse volarly & ulnarly from dorsal radius to insert on the
• Overall TFCC functions at wrist as an extension of distal radius.
• 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.
• 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
RADIOCARPAL CAPSULE & LIGAMENTS
• Has strong but somewhat loose capsule & reinforced by capsular &
• Most ligaments & muscles crossing radiocarpal joint also contributes
to midcarpal joint stability
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 &
• 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.
LIGAMENTS OF THE WRIST COMPLEX
• The ligamentous structure of carpus is responsible for articular
stability as well as guiding & checking motions between & among the
• In general, dorsal ligaments are thin & numerous volar ligaments are
thicker & stronger.
Connects carpals to radius ulna proximally or
Interconnects the carpals
PROPERTIES EXTRINSIC LIGAMENTS INTRINSIC LIGAMENTS
CONNECTION Carpals to radius ulna
proximally & metacarpals
(intercarpals / inrterosseous)
Stronger & less stiff
Lie within synovial lining
Nutrition Contiguous vascularized
Through synovial fluid
Risk of injury High Low
Healing Fast Slow
Accept forces first
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 &
• Ulnocarpal ligament complex – composed of TFCC including articular
disc & meniscus homolog; ulnolunate ligament & ulnar collateral
• 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.
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.
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.
Flexion / extension of the wrist –
• In 3 proximal carpal bones, scaphoid has greatest motion & lunate
• 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.
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.
MUSCLES OF WRIST COMPLEX
Primary role –
• To provide a stable base for hand while permitting positional
adjustments & allow for optimal length tension relationships.
Volar (cause flexion)
Dorsal (cause extension)
• 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.
CARPOMETACARPAL JOINTS OF FINGERS
• Articulation between distal carpal row with 2nd to 5th bases of
• 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
• Deep transverse metacarpal ligament covers 2nd to 4th MC
volarly – tethers together the MC heads & prevents excessive
abduction which contributes to CMC stability.
• 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.
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 &
• 2nd & 3rd CMC joints – essentially immobile – considered to
have 0° of freedom – as it provides fixed & stable axis for 1st, 4th
& 5th MC heads.
• 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
• Longitudinal arch – traverse length of the digits from proximal
• Deep transverse MC ligament contributes to stability of mobile
arches during grip functions.
• 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.
METACARPOPHALANGEAL JOINTS OF FINGERS
• Convex metacarpal head proximally & concave base of 1st
• Condyloid joint with 2° of freedom (flexion/extension &
• 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.
• 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.
• Also called as palmar plates
• Increases joint congruence; provides stability to MCP joints
(limits hyperextension) – so provides indirect support to the
• Composed of fibrocartilage & is firmly attached to base of
• Becomes membranous proximally to blend with volar capsule at
• During MCP extension, the plate adds up the amount of surface
in contact with large MC heads.
• 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.
• 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
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
• Range of passive hyperextension is used to assess flexibility.
• Abduction/adduction is maximal in MCP extension & restricted
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.
• 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.
EXTRINSIC FINGER FLEXORS
• Muscles of fingers & thumb having proximal attachment above
• 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.
• During finger flexion with wrist flexion – FDS & FDP works
• At the proximal phalanx (proximal to PIP), FDP emerges through
split in FDS (camper’s chiasma) & FDS attaches to base of
• 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).
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
• Digital tendon sheaths
• 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
• Flexor pollicis longus (FPL) – pass through carpal tunnel with
FDS & FDP – then radial bursa encases it.
• 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
• 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
• 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
EXTRINSIC FINGER EXTENSORS
• Extrinsic finger extensors are extensor digitorum communis
(EDC), extensor indicis proprius (EIP) & extensor digiti minimi
• Passes from forearm – beneath extensor retinaculum that
maintains proximity of tendons to the joints & improves
• 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.
• EDC, EIP & EDM – extension of MCP joints of fingers via
connection to extensor hood & sagittal band; also causes wrist
• 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)
• 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
• Passive element – oblique retinacular ligament (ORL)
INTRINSIC FINGER MUSCULATURE
• With all attachments distal to radiocarpal joint.
Dorsal & volar interossei muscles :-
• Arise between the MC & are important part of extensor
• 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 &
• 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 &
• 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
• 3 VI muscles – have distal attachment only (lateral band /
• 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.
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
• 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.
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
• The volar migration of interossei is restricted by deep transverse
MC ligament – prevents loss of active tension & serves as
• 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.
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.
• Only muscles in the body that attaches to tendons of other
• 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.
• 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
• 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
• Large range of lumbricals, prevents active insufficiency when
shortening over MCP & IP joints.
• 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
CARPOMETACARPAL JOINT OF THUMB
• Saddle shaped portion of trapezium is concave in sagittal plane
(abduction/adduction) & convex in frontal plane
• 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
• 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
• Dorsoradial & anterior oblique ligaments – key stabilizers of CMC
• 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
• 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.
MCP & IP JOINTS OF THUMB
MCP joint :-
• Between head of 1st MC & base of proximal phalanx.
• Condyloid joint with 2° of freedom – flexion/extension &
• 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.
IP joints :-
• Between head of proximal phalanx & base of distal phalanx.
• Similar to other IP joints of the fngers.
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)
• 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.
• 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
Intrinsic thumb muscles :-
• 5 thenars muscles – originates from carpal bones and flexor
• 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
• FPB has two heads of insertion.
• Large lat. Head attaches to ABL-abduction.
• Medial head attaches to AdP-adduction
• 1ST dorsal interossei- though not consider as a thenar muscle
contributes to thumb function-CMC joint distraction, assist
• 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
• 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.
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
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.
• 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
• Involves use of all finger flexors
• FDP works predominantly
• Interossei muscles – primary MCP
• FPL & thenar muscles- flexion &
adduction of thumb.
• Hypothenar eminence-flex & abduct
• Typically with wrist in neutral /
extension & slight ulnar deviation.
• E.g. turning a door knob.
• Most respect to cylindrical
grip but greater spread of
fingers to encompass the
• More activity of interosseus
for e.g. holding a ball.
• Specialised form of
primarily of fingers.
• Major activity of FDP
• Load – more distally FDP,
• Thumb- moderate to full
• E.g. - carrying a briefcase.
• Contact between two
• MCP & IP joint- in
extension as contigious
MCP joint simultaneously
abduct & adduct
• Extensor musculature pre
• E.g. holding a paper
• Require much finer motor control & more dependent on intact
• 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.
• 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
• Thumb- CMC flexion, abduction &
rotation; MCP & IP joint partially
flexed or extended.
• E.g. holding a foreceps
PAD TO PAD PREHENSION
• 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
• Key grip or lateral pinch.
• Between thumb & side of
• Thumb-more adducted &
less rotated least precise
form of precesion handling.
SIDE TO SIDE PREHENSION
FUNCTIONAL POSITION OF WRIST & HAND
• The functional position is –
• Wrist complex in slight extension (20°) & slight ulnar
• Fingers moderately flexed at MCP joint (45°) & proximal ip
joint (30°) & slightly flexed at distal IP joint