12: Knee and Ankle - Smith Flashcards
_______ condyle deviates from the femoral midline more
medial
longer and narrower condyle
medial femoral condyle
which condyle facilitates the screw-home mechanism
longer medial condyle
which facet on the tibia is longer?
medial
set a little bit more distally than the lateral facet
describe the shape of lateral and medial menisci
medial - c shaped
lateral - complete circle
the menisci in cross section are ________ shaped
triangular
- wider around periphery, thinner near middle
what are the menisci and what are there function?
- fibrocartilaginous structures attached to tibia between femoral condyles
- shock absorption and spacers within joint
in what motion is knee more stable?
extension
what type of joint is the knee joint?
ginglymus (hinged) with two degrees of freedom
*actually has six degrees of freedom (flex/extend, int/ext rotation, ab/adduction)
describe “roll and glide” of knee
- femur will roll and glide during knee flexion to allow the knee to flex without impinging on post tibial plateau
describe “screw-home mechanism”
- external rotation of tibia on femur during last 15-20 degrees of extension OKC
- internal rotation of the femur CKC
- increases osseous stability of the knee joint
- occurs b/c medial femoral condyle has a longer articular surface? (uses it up on lateral side )(also a soft tissue component)
name the muscles of the anterior thigh
quadriceps femoris (vastus medialis, vastus intermedius, vastus lateralis, rectus femoris)
sartorius
articularis genu
function of the anterior thigh muscles in OKC and CKC
OKC = extend knee CKC = pull thigh over stationary tibia
name the muscles of the posterior thigh
hamstrings (semimebranosus, semitendinosus, biceps femoris)
popliteus
posterior thigh muscles function in OKC
- knee joint flexors
- occurs during swing phase
name the muscles of the medial thigh
adductor magnus
adductor longus
adductor brevis
gracilis
(function is minimal in gait)
(lateral is tensor fascia lata which is also minimal function)
contact phase (knee)
- knee joint flexing to absorb shock
- hamstrings contract to flex knee
- quadriceps contract to keep knee from buckling (counteract hamstrings)
midstance phase (knee)
- quads continue contracting and extend knee until body mass passes over the knee joint
- tensor fascia lata externally rotates the tibia on femur during last 20 degrees of knee extension
propulsive phase (knee)
- tensor fascia lata continues to externally rotate the tibia as knee continues to extend
- adductors contract during double support
- hamstrings start to flex preparing for swing phase
swing phase (knee)
- hamstrings flex to allow foot to clear ground
- knee extends the rest of phase preparing for contact
- quadriceps only needed last 20 degrees of knee extension due to whip like action of hip
- hamstrings contract to counteract the quads and keep knee from fully extending
describe the inferior tibiofibular articulation
- fibrous articulation
- strength is increased by interosseous membrane
*** when is ankle joint more stable?
dorsiflexed position (the thicker portion of talus is in the ankle joint)
which part of the talus is wider?
anterior portion is 25% wider
how is the fibula located in relation to tibia?
more distal and posterior to tibia
what is the ankle joint axis (degrees)
- 8 from transverse
- 20-30 from frontal plane
- roughly perpendicular to sagittal plane
what does this mean???
mild abduction with ankle dorsiflexion/ mild adduction with ankle plantarflexion
what motion occurs at ankle joint with dorsiflexion
mild abduction
mild adduction with ankle plantarflexion
transverse plane motion at ankle reduces amount of frontal plane motion needed at subtalar joint
OKC ankle joint
dorsiflexion
plantarflecion
CKC ankle joint
dorsiflexion - tibia moves anterior over planted foot
plantarflexion - tibia moves posterior over planted foot
ankle joint ROM
dorsiflexion 10 +
plantarflexion 45 +
minimum ROM needed at ankle joint
10 dorsiflexion (if less = equinus) 20 plantarflexion
when you repeat ankle dorsiflexion with knee flexed, what do you expect?
- this releases gastroc
- with knee flexed is normally greater than with knee extended
if body can’t get enough sagittal plane motion in ankle where will it go for compensation?
- knee
- MTJ oblique axis
- STJ
looking for joints close with sagittal plane motion
most common rotational deformity below the knee
tibial torsion “ a change in the axial relationship of foot to thigh”
how do you measure rotational deformity below the knee?
- distal tibiofibular axis created by malleoli in relation to axis of knee
- IMPOSSIBLE to measure any amount of actual torsion or twisting of tibia
malleolar positioning as you grow
- birth = 0-5 external malleolar position
- 1 yo = 10
- increases by one degree for each year of age until 12/13
- final = 18-23 degrees of external malleolar positioning
- actual amount of tibial torsion = 13-18
