MS- knee Flashcards
femoral-tibial joint type of joint motion/ DOF accessory motions (2)
- complex (because of meniscus)
- modified hinge joint, dual condylar
- does flex/extend (in transverse axis)
- accessory motions: rotation and
aB/aD from valgus force
femoral- patella joint
type of joint
sellar joint, modified plane joint
resting position of knee
closed pack position of knee
capsular patter
resting position- 25-40deg of flexion
closed pack- max ext (with ER of tibia) screw home mechanism
capsular pattern- lose flex > ext
physiological valgus
anatomy of femur => why favored position is flexion (2)
physiological valgus
- femoral neck overhangs shaft
- femur is angled 5-10 degrees of vertical
articular surfaces of tibial condyle
why favored position is flexion (2)
medial and lateral condyle convexity
relative sizes
flexion is favored because…
- retroversion of tibial condyles (inclined posteriorly)
- retroflexion = tib bent convex for muscle bellies
medial condyle is biconcave
lateral condyle is concave in frontal plane
convex in saggital plane
medial condyle 50% larger > lateral
articular surface 3x thicker > lateral (b/c weight bearing forces and angle of inclination)
femoral condyles
shape
relative sizes to each other
and to tibial condyle
medial vs. lateral
WB stressesbi-convex, longer A/P than M/L
2x as long as tibial condyles because of “runner”
medial condyle juts out more and is narrower which allows knee to be horizontal b/c of angle of inclination => better distribution of force
lateral condyle more in line w/ shaft of femur
WB stresses med and lateral equally in double stance
arthrokinematics of knee joint sitting down (extension -> flexion)
femoral condyles have a “runner” that make it 2x the length of tibial condyle
Ext -> flexion femoral condyles roll posterior w/o gliding, then ACL slides femur anterior
sliding = new points of contact on each bone
** sliding is why its a modified hinge joint*
femoral condyle movements during gait &
how much each moves
condyles mostly roll during gait, which is very efficient
lat condyle moves 20 deg
med condyle moves 10-15 deg
knee capsule
superlative
anterior attachements (4)
M/L attachements (4)
- largest capsule b/c largest joint in our body
- has window anterior for patella
attach anterior: tib med/lateral tibal condyles med/lateral patella surfaces extensor retinaculum
posterior: at level of popliteal notch
med/lateral retinaculum
IT band (not position dependent)
VMO and VL link fascia -> muscle
bicep femoris link fascia -> muscle
ITB relationship to medial collateral
IT band adds secondary reinforcement to MCL because they are complete opposite alignments
not postion dependent so maintains tension throughout ROM
Plicae
what is it
3 compartments and whats in them
left over compartments from embryological development
3 compartments
1. superior compartment - suprapatellar bursa
2. infrapatella plica (fold) = inferior aspect of femur- filled with fatpad (infrapatellar fatpad)
can become edemaneous mostly in people who work on their hands and knees
flex- gastroc pushed fluid forward so palpable
extend - rec fem pushes fluid back
3. mediopatella plica - palpable
6 knee bursae
names and locations
- suprapatellar bursa - quad bursa (located in superior plicae)
- prepatellar bursa - under skin, anterior to patella
- infrapatellar bursa- superficial, anterior to patella ligament
- deep infrapatellar bursa- under patella ligament
- gastrocnemius - under head of gastroc
- popliteus - btwn popliteus and femoral condyle
these two are hard to differentiate but gastroc bursitis is more common
meniscus
shapes
purposes
vascularity
incomplete rings
lateral - ant/post horns closer together => more circular
medial - more half moon shape
purpose: to increase radius of curvature of tibial condyle, distribute WB and decrease friction
inner 2/3 avascular
meniscal transmission of forces
(in flexion and extension)
and what happens if loss of cartilage
50% of force in extension
80% of force in flexion
so loss of cartilage =>
increase 2x force on femur
increase 6-7x force on tibia
common meniscal attachments
anterior horns
to tib (2)
to patella (2)
- intercondylar tubercles of tibia
- coronary ligaments (meniscotibial) are comprised of fibers of jt capsule
- anterior horns attached to eachother by transverse ligament
attach to patella by
- patellomeniscal
- patellotibial ligaments (capsule thickenings)
3 lateral meniscal attachements
connections are considered ______ => _______
- posterior cruciate ligament
- popliteus muscle (vis coronary lig & posterior capsule)
- femoal condyles
connections are considered loose => less injuries
3 medial meniscal attachements
- medial collateral ligament -deep fibers
direct attachement - semimembranous (indirect, thru capsule)
- anterior horn from ACL
connections are tight => more tears
unhappy triad of knee injuries
- ACL
- MCL
- MM
what happens if you lose degrees of Q angle?
Q angle is angle femur makes with middle of patella
if lose degrees of Q angle => increase 50% compression on medial knee
movement of meniscus in flexion and extension
lateral menisci movement vs medial
menisci follow point of contact btwn femoral and tibial condyles (pushed by femur)
in flexion => posterior
in extension => anterior
lateral menisci moves 2x > medial
movement of menisci in rotation
in lateral rotation
how do they get injured?
lateral rotation: lateral meniscus is pulled anteriorly and medial pulled posterior
because pushed by femur
injured if they dont follow movement of femoral condyles- can become wedge btwn femoral and tibial condyles
patella
shape
facets (#)
purpose
- triangular shaped
- 7 facets, 3 on each side and odd facet
- purpose- improve efficiency of extension; increases mechanical advantage of quads by 25%
movement of patella in flexion
ration of patella to patella tendon
in flexion patella moves inferiorly 2x its length
patella : patella tendon 1:1
patella displacements (4)
- alta = superior 20% longer tendon > patella
- baja = inferior patella 20% > tendon
- squinting = medial
- bull frog eyes = lateral
patella movement on tibia
during medial rotation
during lateral rotation
during medial rotation: femur is lateral on tib and pulls patella laterally
during lateral rotation: femur is medial on tib and pulls patella medially
b/c patella is stuck btwn femoral condyles
transverse ligament
attaches anterior horns of menisci
attached to patella by strands of infrapatellar fat pads
MCL
attachements
separate from capsule?
extra important facts about what it blends with
medial fem condyle -> upper tib ( posterior to pes anserine)
anterior fibers are separate from capsule posterior fibers (deep) blend with MM
superficial band blends with posteromedial corner of capsule = posterior oblique ligament = popliteal complex
LCL
Location
Part of capsule?
Bands
Purpose (2)
- Lateral aspect of lat condyle => head of fib
- **free of capsule
- 3 bands, ant, posterior and middle
Purpose:
Helps prevent lat rotation of tib
Helps ACL prevent hyperext
Posterior-lateral support of capsule (4)
- PCL
- Bicep femoris
- IT
- Popliteus
transverse stability… What happens to knee after violent valgus force?
knee already had physiological valgus, intense force can => fracture dislocation of lateral tibial condyle and rupture MCL
A/P stability of knee
in flexion
in hyperextension
in slight flexion: body weight is behind axis so quads are essential
In hyperextension: posterior capsule checks ligamentous stretch and prevents genu recurvatum
ACL
direction
max taught degrees
2 bands- when are they taut and lax?
how helpful is it? (%) , when?
runs superior posterior and lateral
max taught 0-20 and 70-90
Anteromedial band max tension 70 degrees
Posterolateral band max tension in extension, lax 70 degrees flexion
takes 87% of load with any translation in extended knee
visco-elastic => adjusts to load and length
very rich vascular supply
PCL
Direction
Superlative, why is it important
2 bands and when they are max taut
runs medial, anterior & superior
strongest stabilizer in knee, 93% of load in extended knee w/ posterior translation
2 bands:
anteromedial: lax in ext, max taut 80- 90 deg flex
posterolateral: taut in extension, lax at 80-90 deg flexion
When is flexed knee maximally displaced?
75-90 deg flexion
Cruciates
relationship to capsule
relative sizes
roles during flex & ext
- Considered thickenings of capsule
- post cruciate 2/3 < ant
- during flexion ACL slides femoral condyle anterior
- During extension PCL glides femoral condyle posterior
posterior capsular ligaments
Posteromedial aspect reinforced by….
Posterolateral aspect reinforced by….
When are they max taut?
What other movements do they add stability to?
Posteromedial aspect = oblique popliteal ligament, which is reinforced by tendinous expansion of semi-mem + pes anserine
Posterolateral aspect = arcuate popliteal ligament + bicep fem
All taut in extension
Help valgus and varus stability
Rotational stability…
What winds/ unwinds with med/ lat rotation of tibia?
collaterals and cruciates
IR unwinds collaterals
ER winds collaterals
medial rotation tightens cruciates (ACL wraps around PCL during IR)
lateral rotation relaxes cruciates
Ottawa knee rules
definition
5 things
used to determine necessity of ordering x-ray
- pt >55 yo
- isolated tenderness over fibula head
- isolated tenderness over patella
- unable to flex knee to 90 degrees
- unable to WB immediately and in ER
Q angle
normal for males and females
how to measure
10-15 degree in males
10-19 in females
0 in flexion** doesnt exist in flexion, must be done in extension (standing)
Lachman test
ACL
PCL
ACL:
pt supine with slight ER and 20 degrees of flexion
=> testing posterolateral band of ACL
PCL:
pt prone (NO ER) and 20 degrees of flexion
=> testing posterolateral band of PCL
Slocum test (2)
anteromedial stability-
anterior drawer with 15 degrees lateral rotation
anterolateral stability-
anterior drawer with 30 degrees internal rotation
lateral pivot shift test pt position hand position what we do positive sign
- pt supine; hip 20
knee 5
abducted - hold behind head of fib and lateral mall
- medially rotate tib and add valgus
- adding valgus will sublux tib
- flex knee - ITB will act as flexor and pull tib back in
hear a clunk
hughstons test (2)
posteriomedial instability-
posterior drawer with medial rotation
posteriolateral instability-
posterior drawer with ER
“hughston is a pain in the ass” = posterior
meiniscal tests
- tenderness along joint line
- squat with feet IR = pain in lateral meniscus
- squat with feet in ER = pain in medial meniscus
- duckwalk/ childress sign = medial meniscus
- McMurrys test for posterior horn
- apleys test - either meniscus or ligaments
- bounce home test
- helfet test = screw home mechanism
McMurrys test (2)
to test medial meniscus posterior horn:
pt supine, ER, valgus force
to test lateral meniscus posterior horn:
pt supine, internal rotation, varus force
apleys test (2)
- prone, knee flexed to 90, compress and grind knee
2. distract and IR/ER tib to check for ligamentous instability
meniscal swelling tests (3)
- (s)wipe test
- patella tap- check for ballotable patella
- indentation test- E -> flexion, lose normal indentation around patella
plica test
flex knee 30 degrees, push patella medially… will feel pain because compressing plica
tests for patellofemoral dysfunction (5)
- quad sets
- grinding
- clarkes sign
- waldron test
- fairbanks test- apprehension for patella dislocation
causes of patellofemoral dysfunction
any time the patells is not tracking correctly in intrapatellar groove => problems on posterior aspect of patella
this can cause erosion of cartilage = chondromalacia
referred pain of knee (2)
and what posterior pain usually is
L2-L3 - radiate anterior
S1, S2 hip L3- radiate posterior- rare usually anterior knee pain
posterior knee pain is usually bakers cyst- from gastroc or politeus bursa, very visible
predictor variables for knee OA (6)
must have knee pain + >3 variables
- > 50
- morning stiffness < 30min
- crepitus with active motion
- bony tenderness with palpation along joint line
- bony enlargement
- no palpable warmth (b/c not systemic)
McConnell
normal patella alignment
in ext
- center in groove by 30 deg flexion (resting positon)
2. lateral overhand is okay in extension
according to McConnell… forces acting on patella
lateral (3)
medial (2)
lateral:
lateral retinaculum which blends with
ITB
vastus lateralis
*usually tight lateral side
medial side:
medial retinaculum
VMO
factors affecting patella alignment (McConnell) 6
- increased Q angle
- tight lateral structures
- tight gastrocs or hamstrings
- excessive pronation of foot
- patella alta (high patella = long tendon)
- VMO insufficiency
patella movement terminology and nomenclature glide tilt rotation anteroposterior
glide- M -> L
tilt - around Y axis
named for lower side/ side its tilting to
rotation- inferior pole around z axis
named for direction of inferior pole
L most common
anteroposterior- inferior pole around x axis
named for inferior pole
posterior most common
McConnell treatment of PFP
- stretch tight lateral structures (before taping)
- patient self stretch
- passively position with tape
