knee Flashcards
week 9
what is the mechanical axis also known as?
weightbearing line
what is the mechanical axis
a weightbearing line that is drawn from the middle of the calcaneus to the head of the femur
where should the weightbearing line pass through?
knee joint center
tibiofemoral alignment
what is the normal angulation of femur?
femur is 5° off of vertical = 185°
tibiofemoral alignment - knee
what is the genu valgum degree?
> 185°
bigger angle!!
tibiofemoral alignment -knee
what is genu varum degree?
≤ 175°
smaller angle
knee
what are the functions of the menisci?
- shock absorption (50-70% WB –> redistrubutes back)
- increased congruence of the joint (stability)
- lubricates the joint (reduce friction) –> fluid filled barrier
- provides proprioception
knee
what are the zones of vascularization in the meniscus?
red zone: 25% of meniscus
pink zone: 25%-33% of meniscus
white zone: 33%-50% of meniscus
as an adult
knee
what zone of the meniscus takes the most load, and takes the load first?
white zone
knee
mensical tears can be?
acute or chronic
knee
what makes a meniscal tear acute? chronic?
acute - often a twisting and loading component
chronic - older patietnes
knee
what are symptoms of a meniscal tear?
- popping, locking
- giving way
- pain with activites (e.g. stair climbing)
- pain and tenderness with palpation at the joint line
- effusion (swelling) –> intracapsular so local to knee
- difficulties with full extension
- pain with full flexion or limited ROM
- antalgic gait
knee
where does the ACL orignate and attach?
originate: posteriomedial aspect of the lateral femoral condyle
attach: tibia on the lateral and anterior aspect of the medial intercondylar tibial spine
knee
Ground reaction force vector (GRFV) is the sum of what?
2 or 3 directions
knee
what is needed for the ground reaction force to be calculated?
first the body is seperated into two masses: knee down and the rest of body
3 things needed:
- contact time - heel on ground
- limb was in air (body in air -aerial time)
- limb acceleration –> determines GRF
knee
does the lateral or medial meniscus have more artiuclar cartilage? why?
lateral meniscus has more articular cartilge becasue it moves more A and P than medial
knee
the medial meniscus and medial collateral ligament have an attachment but the lateral does not. what does this attachment do?
aides in stability
knee
what orthopedic procedure is the most common in the US for meniscus?
partial medial menisectomy
knee
what is the structure of the ACL from its origin to attachment site?
twists laterally as it travels distally
knee
what are the 2 bundles of the ACL?
anteromedial bundle (AMB)
posterolateral bundle (PLB)
bundles - think tibial insertions
knee
when is the anteromedial bundle slack?
in extension
knee
when is the posterolateral bundle of ACL slack?
in flexion
knee
the ACL remains fairly taut throught knee range of motion. what degree range is the ACL as a whole the most taut?
15°-30° of knee flexion
knee
although the ACL remains failry taut throughout knee ROM when is the ACL least taut?
30°-60° of knee flexion
knee
is the ACL intracapsular or extracapsular?
intracapsualr
knee
ACL - list the function
important stabilizer of the knee joint especially in the sagittal plane
knee
ACL function - most fibers of the ACL resist extension by resisting:
- excessive anterior tibial translation
- posterior translation of the femur
- or a combo of both
- resists extreme varus, valgus and axial rotation
- the anterior/posterior translation matters arthrokinematiclly but not for the sake of ligament
knee
ACL - injury mechanisms
plant and cut:
one legged landing, often in combination with:
- large valgus producting force
- large axial rotation torque
- knee close to full extension (opp, already alot of load)
severe hyperextension of the knee
knee
PCL - function:
origin and insertion
orignates: lateral aspect of the medial femoral condyle
attaches: posterior tibial surface, between the posterior horns of the two menisci
knee
PCL - structure
greater cross-sectional area than the ACL
knee
PCL - two bundles
think tibial insertions
Anterolateral Bundle (ALB)
Posteromedial bundle (PMB)
inbetween flexion/extension both taut
knee
how much bigger is the PCL compared to ACL?
150%
knee
PCL - resists knee flexion.
is also primary restraint for what? also resists what?
primary restraint for posterior translation of the tibia
- also resists anterior translation of the femur and the combination of both
- resists extreme varus, valgus and axial rotation
knee
PCL - injury mechanims
- forceful posterior translation of the tibia/anterior translation of the femur while knee is flexed
- large axial rotation or valgus-varus force with foot planted and knee in flexion
- falling on fully flexed knee with ankle fully plantar flexed
- severe hyperextension of the knee
knee
what is a dashboard injury?
PCL injury - forceful posterior translation of the tibia/anteror translation of the femur while knee is flexed
knee
what works against and unloads PCL?
quadriceps
knee
what increases load on PCL?
when you unload ACL you load PCL -there is a balance
hamstring, gastrocnemius
knee
MCL function - superficial fibers
- arise from the medial femoral epicondyle
- insert into the medial aspect of proximal tibia
knee
MCL function - deep fibers
- arise from the inferior aspect of the medial femoral epicondyle
- inserst into the posterior-medial joint capsule, medial meniscus, and tendon of the semimembranosus
knee
the MCL has a rich blood supply which means the MCL has?
a good capacity to heal
knee
MCL function - resists what 2 motions?
- resists knee valgus (abduction) and knee external rotation
- secondary role in resisting anterior translation of the tibia
knee
the MCL tearing will significanlty increase what?
ACL load
knee
MCL injury mechanisms -
- valgus producing force with the foot planted
- severe hyperextension of the knee
knee
is the LCL intra or extra capsular? why?
extracapsular - does not attach to lateral meniscus
knee
LCL origination and attachment?
arises at lateral femoral epicondyle
inserts into fibular head (conjoined tendon with the biceps femoris)
knee
LCL blood supply?
has good blood supply but does not heal as quickly as the MCL
knee
LCL function?
resists knee varus (adduction), knee extension and internal rotation
(to lesser degree external rotation too)
primary varus stabilizer of the knee
knee
LCL- injury mechanisms
- varus prodcuing force with the foot planted
- severe hyperextension of the knee
knee
acl reconstruction is often misdiagnosed due to what?
due to x rays beingtaken to see if there is a fracture. 1 of 3 experience subsequent rupture after ACL reconstruction
