Joints And Ligaments of the Thumb Flashcards
CMC joint of the thumb
articulation of the trapezium and base of the 1st metacarpal
the trapezium is ______ and the 1st metacarpal is ______ (CMC joint)
trapezium is concave in the sagittal plane and convex in the frontal plane
1st metacarpal has a congruent shape
what kind of joint is the CMC joint
saddle joint
2 degrees of freedom
what does the CMC joint allow
flexion/extension
ABD/ADD
Rotation
flexion/extension in CMC joint
in the frontal plane around an oblique A/P axis
flexion/extension CMC join ROM
flexion –> 0-15 degrees
extension –> 0-20 degrees
a lot of variability
ABD/ADD in the CMC joint
sagittal plane around an oblique frontal axis
ABD/ADD ROM CMC joint
0-70 degrees
rotation CMC joint
a combination motion
termed opposition and reposition
important for hand function
normal ROM is top of thumb to tip of other fingers
ligaments of CMC joint
radial, ulnar, volar and dorsal ligaments that reinforce the capsule
intermetacarpal ligament
intermetacarpal ligament CMC joint
tethers the bases of the 1st and 2nd metacarpals which limits extreme motions of base of 1st metacarpal
joint capsule CMC joint
relatively lax and reinforced by ligaments
MCP joint of the thumb
articulation is between the concave base of proximal phalange articulating w/ the convex head of the first metacarpal
moves concave on convex (BM, roll and glide in the same direction)
what type of joint is the MCP joint
condyloid joint with 2 degrees of freedom
MCP joint allows for
flexion/extension
ABD/ADD
Rotation
flexion/extension MCP joint
frontal plane around an AP axis
Normal ROM: 0-75 or 80 degrees
ABD/ADD MCP joint
sagittal plane around frontal axis
we don’t need this joint to move alone b/c of CMC joint ABD/ADD
Normal ROM is next to nothing
rotation at MCP joint
is passive movement allowed by the lax capsule
ligaments of MCP joint
radial and ulnar collateral ligaments
accessory collateral ligament
radial and ulnar collateral ligaments
run obliquely from dorsal aspect of metacarpal to ventral aspect of the base of proximal phalanx
are taut in flexion and lax in extension
accessory collateral ligaments
run from dorsal aspect of metacarpal to palmar plate
are slack in flexion
joint capsule MCP joint
moderately loose and lined by synovial membrane
volar plate MCP joint
is fibrocartilage and firmly attached to the phalange
similar in form and function to volar plates of MCP’s of fingers
sesamoid bone MCP joint
presence of 2 sesamoid bones provides reinforcement extra capsularly on the volar surface
appear at approximately 12 years of age
the inter-sesamoid ligaments secure the bones the joint
CMC joint arthrokinematics flexion/extension
concave on convex
everything in the same direction w/in the frontal plane
ABD/ADD arthrokinematics
convex on concave
BM, roll –> same direction
glide –> opposite direction
w/in the sagittal plane***
