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fabella
- a sesamoid bone located inside the gastrocnemius lateral head tendon on the posterior side of the knee
- in about 25% of people
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which is bigger - the femoral-tibia joint or the femoral-patella joint?
fem-tib
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kind of joint w >2 bones?
compound
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kind of joint w meniscus or articular disc?
complex
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femoral-tibial joint is what kind of mechanical joint? what type of joint (regarding how it moves)? how many degrees of freedom?
- complex due to the meniscus
- ginglymus - modified hinge
- 3 DoF, but mainly just 1 - flex/ext around transverse axis
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type of contour of the knee joint?
dual condylar
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1st DoF in knee is ext/flex. What are the 2nd and 3rd degrees?
- 2nd: rotation - happens only when knee is flexed - it's impossible in ext
- 3rd: abd/add - not voluntary - happens w wt bearing
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femoral-pattela joint - joint type - 2 descriptors
- sellar/saddle: bc opposing surfaces are reciprocally concave-convex
- modified plane joint: because it slides
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resting pos of knee
25-40 degrees flexion
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close-packed pos of knee
max ext w max ER
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capsular pattern of knee
- more limitation of flex (90) than ext (5)
- seldom LOM in rot unless gros restriction
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will knee contractures have capsular patterns?
they're secondary to contractile structure troubles, so no, they're non-capsular
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femoral neck overhangs shaft 170-175 degrees creating...?
physiological valgus
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femur is angled off __ from the vertical
5-10 degrees
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orientation of the femoral and tibial condyles favor what motion of the knee?
flexion - this goes back to our quadruped days
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retroversion as it relates to the articular surfaces of the knee
the tibial condyles incline posteriorly
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retroflexion as it applies to the articular surfaces of the knee
the tibia is bent to be concave posteriorly ... so when the knee is flexed, this place fills with the gastroc
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femoral condyles basic shap
- pulley shaped
- bi-convex
- longer in A/P than M/L
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compare the med and lat fem condyles
- med: justs out more, narrower, angled medially
- lat: more in line w shaft (secondary to obliquity of shaft of femur)
- wt bearing: equally deistributed in bilat stance despite femur being angled to the side bc the med condyle is bigger and extends more distally
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concavity and convexity of tibial condyles
- med condyle is biconcave (in AP and ML directions)
- lat condyle is concave in frontal plane and flatter in sagital plane
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compare the articular surface of the med condyle with that of lat
med articular surface is 50% larger and the articular cartilage is 3x thicker.... so we see more degenerative changes on the medial side
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in axial rotaion of btwn the tibia and femur, what acts as the pivot?
the intercondylar tubercles of the tibia -- lodges in the intercondylar notch of the femur
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rel of circumferential length of femoral condyles ot tibial condyles -- and implication
fem condyles are 2x as long as length of tib condyles --- so you need sliding/gliding to access diff pts of contact
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arthrokinematics in ext to flex
- full ext - fem condyles begin to roll w/o glide (first 10-25 degrees)
- then slide comes in in opp dir
- at end of motion - slide w/o glide -- or glide dominates? my notes are confusing
(aaxis isn't relatively fixed. It moves a considerable extent thru ROM)
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arthrokinematics in rotation
lat rot of tibia on femur: lat fem condyle moves forward over lat tibial condyle, and med fem condyle moves back
during neutral pos for axial rot w knee flexed: post fem condyles in contact w mid part of tib condyles
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plane synovial joint
- permits only sliding/gliding
- opposed surfaces of bones are almost flat
- superior tibio-fubular joint
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10% thing about the sup tib-fib joint capsule
- in 10% of population, the capsule is cont with the fem-tib joint
- for everyone else it has its own capsule
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plicae
- seams in the synovium
- feels like a guitar sting
- infrapatella plica
- mediopatella plica
- ant inf plica
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about the IT band length and which lig it most helps
- it's always same length regardless of position
- LCL
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infrapatella fold is an empty space bounded by what 3?
filled w what?
- ant intercondylar fossa of tibia
- ligamentum patella
- inf aspect of patella surface of femur
adipose tissue - the infrapatellar pad (infraptellar plica is in there)
this region gets a lot of fluid/edema
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popliteus muscle attachments + action
- lateral surface of lateral condyle of femur + intracapsular outer margin of lateral meniscus of knee joint-->posterior surface of shaft of medial tibia above soleal line
- flexion + tibial IR
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location of infrapatellar and deep infrapatellar bursae
- infrapatellar - under the patella but superficial
- deep inf - deeper, in the fat pad area
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