knee Flashcards
tibiofemoral joint - joint type
synovial double condyloid/modified hinge
t/n: this is because of voluntary control of movement is possible in 2 planes (saggital/transverse)
tibiofemoral joint (2) planes
(2) DOF:
1) sagittal - flex/ext.
2) transverse plane - tibial ER/IR
patellofemoral joint - joint type
non-synovial joint/false joint
tibiofemoral joint anatomy (femoral condyles)
FEMORAL CONDYLES
larger medial FEM condyle
- greater radius of curvature
- shifted a bit POSTERIROLY/projects more DISTALLY
lateral FEM condyle
- shifted ANTERIORLY (more directly in line with the shaft of femur)
t/n: there is some ROTATORY movement happening because of IMBALANCE when it comes to lat/med condyles SHAPE
tibiofemoral joint anatomy (tibial condyles & tibial plateaus)
TIBIAL CONDYLES
larger medial TIB condyle / smaller lateral TIB condyle (same w/ femoral)
TIBIAL PLATEAUS
larger medial TIB plateau / smaller lateral TIB plateau (in order to match two tibial condyles)
(3) tibiofemoral alignments
1) physiological valgus angle/anatomical longitudinal axis of femur
2) mechanical axis/weight-bearing line
3) q angle/quadriceps angle
physiologic valgus angle
- anatomical/longitudinal axis of femur
- normal values: 175-185 (180 ave)
- crosses MIDLINE
genu valgum
- knock knees
- greater than 185 deg
- MEDIAL COLL. ligament STRETCHED
- LATERAL COLL. ligament COMPRESSED
genu varum
- bow legs
- lesser than 185 deg
- MEDIAL COLL. ligament COMPRESSED
- LATERAL COLL. ligament STRETCHED
mechanical axis/weight-bearing line
- transmits weight DOWN TO LE / passes through MECHANICAL AXIS
- passes CENTER OF
1) hip joint
2) knee joint
3) ankle joint
mechanical axis during single-leg stance
- shifts MEDIALLY
- MEDIAL aspect COMPRESSIVE FORCE / LATERAL aspect MORE DESTRUCTIVE/TENSILE FORCE
Q angle
- quadriceps angle
- normal value: 10-15 deg
- male ave: 14 deg / female ave: 17 deg (wider pelvis/short stature)
- INTERSECTION lines FROM:
1) ASIS to midpoint of patella
2) tibial tubercle to midpoint of patella - represents vector for combined pull of quads fem & patellar tendon
- will influence the amt. of force that quadriceps muscle & patellar tendon are generating
menisci of the knee characteristics
- fibrocartilaginous discs (gel-like structure)
- reduces frictional forces
- increases concavity of tibial plateau > increases congruence of joint
- wb function:
1) shock absorber
2) pressure distribution
medial vs lateral menisci (anatomical config.)
MEDIAL
- larger
- C shape
- thick on the outside (on periphery)/thinner on central area
LATERAL
- smaller (almost 4/5 of a circle)
- thick on outside (on periphery)/thinner on central area
(4) menisci attachments
1) transverse ligament
- connecting 2 anterior horns of lateral and medial meniscus
2) coronary ligaments
- stabilize meniscus between femur and tibia (imagine putting a coin in that space > absence of coronary lig. > meniscus unstable) / in place no matter what movement
3) joint capsules
4) tendons of some muscles
medial menisci vs lateral menisci (attachments)
MEDIAL
- MCL
- ACL (anterior horn)
- PCL (posterior horn)
- semimembranosus
LATERAL
- LCL
- ACL (common tibial attachment)
- popliteus
t/n: meniscal motion is influenced by these structures > will dictate stabilization of menisci
medial menisci vs lateral menisci (stability/mobility)
medial meniscus = more attachments = more stable
- medial meniscus being stable cannot go/move with knee joint = has greater risk for injuries
lateral meniscus = less attachments = more mobile
- since LE has many functional activities/involves lots of movements, it requires movement of menisci (lateral)
knee joint OPP/CPP
OPP
- slight knee flexion (25-30 deg)
- not stretched too much
CPP (bony/lig)
- full knee ext.
- tibial ER
knee joint capsule characteristics
- very thick
- has 2 layers
knee joint capsule (2) layers
1) fibrous capsule/layer
2) synovial membrane/sheath
knee joint capsule: fibrous capsule/layer (characteristics & function)
- superficial
- attached to distal femur/proximal tibia
- attaches to patella/quadriceps tendon/patellar tendon
- creates TIGHT seal
- is part of EXTENSOR RETINACULUM
- ENCLOSES synovial fluid
knee extensor retinaculum (3) contents
1) lateral patellar retinaculum
2) medial patellar retinaculum
3) fibrous capsule
knee joint capsule: synovial membrane/sheath (characteristics & function)
- deeper
- thinner
- SECRETE and ABSORB synovial fluid
knee joint: synovial fluid
- moves when we move tibiofemoral joint (extension = anteriorly / flexion = posteriorly)
- semi-flexed position (usual position of comfort) = equal distribution of fluid / does not impinge any pain-sensitive structures being controlled on CENTRAL area
t/n: if knee joint is injured > inflammation > swelling > excessive fluid in synovial cavity > compression of structures in joint
knee fat pads
- fatty soft tissues found in the knee joint
- reduce frictional forces (between tendon and bone/muscle and bone)
- acts as shock absorbers (when too much pressure is present in the joint, e.g. when you kneel)
- very rich in nerve innervation > compressed too much > pain (fat pad impingement syndrome)
- FOUND SUPERIOR on the PATELLA
(3) knee fat pads
1) anterior suprapatellar fat pad (anterior to quadriceps tendon)
2) posterior suprapatellar fat pad (posterior to quadriceps tendon)
3) infrapatellar (hoffa’s) fat pad
patellar plicae
- joint synovial membrane
- embryonic stage > septum > separate 2 lateral and medial compartments of knee
- plicae stage > synovial septum resorbed > remnants of synovium > patellar plicae
patellar plicae syndrome
- patellar plicae (pain-sensitive structures) irritated/inflamed
(4) patellar plicae locations
inferior (infrapatellar) > superior (suprapatellar) > medial > lateral
*commonly found inferiorly (infrapatellar)
knee bursa
- balloon-like structure
- reduce fictional forces
(5) bursa of the knee
1) prepatellar bursa (between patella & skin)
- if inflamed, popeye’s knee / injured, housemaid’s knee
2) suprapatellar bursa (between quadriceps tendon & femur)
3) infrapatellar bursa (superficial & deep)
- if inflamed, clergyman’s knee
4) pes anserinus (subsartoial bursa/pes anserinus muscles)
5) popliteal bursa (small bursa posteriorly)
(4) knee joint ligament groups
1) collateral ligaments (LCL/MCL)
2) cruciate ligaments (anterior/posterior)
3) ligaments of posterior (joint) capsule
4) meniscofemoral ligament
lateral collateral ligament (LCL)
- fibular collarteral ligament
- lateral side > controls varus forces
- merges with biceps femoris (tendon) > CONJOINED TENDONS
- provides SECONDARY RESTRAINT for TIBIAL ER
medial collateral ligament (MCL)
- controls valgus forces (PRIMARY)
- RESTRAINT ANTERIOR tibial TRANSLATION (SECONDARY)
anterior cruciate ligament (ACL)
- from MEDIAL TIBIAL PLAT
- moves upwards > superior > posterior > lateral
- attached to MEDIAL SURFACE of LAT. FEM CONDYLE
True/False:
Both ACL & PCL are intracapsular & extrasynovial.
true
t/n: intracapsular = inside capsule / extrasynovial = outside synovium
ACL functions (unidirectional control)
- prevent excessive ANTERIOR translation of the tibia on fixed femur
- prevent excessive POSTERIOR translation of femur on fixed tibia
- prevent hyperextension of the knee
ACL functions (multidirectional control)
- provides STABILIZATION (ANTEROLAT/ANTEROMED)
(2) ACL bundles
1) anteromedial bundle (AMB)
- taut in knee flex. >90 degrees (maximal knee flexion)
- also taut in hyperEXT. (but PLB more taut)
2) posterolateral bundle (PLB)
- taut in hyperEXT.
True/False:
Both bundles of ACL are taut in hyperextension.
true
t/n: that’s why if we have hyperext. injury, you can injure both bundles of ACL
posterior cruciate ligament (PCL)
- from LATERAL TIBIAL PLATEAU
- moves up sup > bit forward ant > medial
- attached to LATERAL SURFACE of MED. CONDYLE
PCL functions (unidirectional)
- prevent excessive posterior translation of tibia on fixed femur
- prevent excessive anterior translation of femur on fixed tibia
PCL functions (multidirectional)
- provides STABILIZATION (POSTEROMED/POSTEROLAT)
- secondarily RESISTS varus forces
- prevent too much tibial IR
True/False:
PCL cross-sectional area > ACL
true
t/n: that’s why ACL is more injured
(3) ligaments of posterior capsule
1) oblique popliteal ligament
2) posterior oblique ligament
3) arcuate ligament
oblique popliteal ligament (characteristics & functions)
- expansion of semimemb. muscle
- merges with (posterior) joint capsule > posteromedial tibial condyle
- support joint posteromedially
posterior oblique ligament
- attached to adductor tubercle
- attached to MCL > posteromedial tibia > medial meniscus
- support joint posteromedially
arcuate ligament
- support joint posterolaterally
- (2) branches: medial / lateral
meniscofemoral ligament
- not true ligament (misnomer)
- attached from meniscus going to femur
- from lateral meniscus > PCL > medial femoral condyle
meniscofemoral ligament (2) fibers
1) anterior = ligament of Humphry
2) posterior = ligament of Wrisberg
knee arthrokinematics (OKC)
- concave tibia moving
extension
- tibia roll ANT. / glide ANT.
flexion
- tibia roll POST. / glide POST.
knee arthrokinematics (CKC)
- femur moving
extension
- condyle roll ANT. / glide POST.
flexion
- condyle roll POST. / glide ANT.
everything about Screw Home Mechanism
EXTENSION
- also called “terminal knee rotation/extension” / “locking mechanism of the knee”
- very important FUNCTIONALLY (e.g. ambulation) so that knee doesn’t buckle
- last 20-30 degrees of extension
- tibial ER
FLEXION
- unlocking knee
- tibial IR
-
(3) factors of Screw Home Mechanism
1) bone & joint (larger medial femoral condyles/medial plateau = GREATER ARC MOTION for knee flex/ext)
2) ligament (obliquity of ACL = generate SOME ROTATIONAL MOTION)
3) muscle (obliquity of Q-angle = lateral pull of quadriceps)
True/False:
Muscle responsible for tibial IR during unlocking of the knee (flexion) is Popliteus.
true
t/n: no muscle is active during tibial ER, locking of the knee (extension) but rather supported by femoral condyles/tibial plateau/passive tension of ACL/Q-Angle
(5) compressive forces on the knee (and their BW contribution)
1) gait (ambulation) = 2x BW
2) stair climbing = 2x BW
3) running = 3-4x BW
4) genu varum = medial compressed > lateral
5) genu valgum = lateral compressed > medial
normal knee ROM (knee flexion/deep squats/normal gait/stair ascent/stair descent/sitting down/hyperext)
F: 130-140 (135)
DS: 160
G: 60-70
SA: 80
SD: 110-120
SIT: >=90
H: -5
patella
- largest sesamoid boin
- inverted triangle (apex = inferior)
- has (2) vertical ridges
- contribute to anatomic pully of quadriceps
- increased moment arm / increased torque generation capacity of quads fem.
patella vertical ridge
- posterior patella
- divided to med. and lat. facets
patella 2nd vertical ridge
- separate med. and odd facets
(5) facets of patella
1) sup
2) inf
3) med
4) lat
5) odd
patellar contact
knee extended = inferior pole > femur
20 deg flexion = inferior facet compressive contact
45 deg flexion = middle portion compressive contact
90 deg flexion = superior facet compressive contact
> 90 degrees (135 deg) flexion = more contact > odd facet
insall-salvati index
- patellar height
- ratio of length of patellar tendon to length of patella
- normal ratio: 1:1 (equal)
patella alta
> 1:1 / >1:2
- patella situated higher
- patellar tendon length increases
patella baja
< 1:1 / <0.8
- patella situated lower
- patellar tendon length decreases
(3) patellar motion
1) upwards
2) downwards
3) side to side
patellar rotational movements (3) axis
(2) X axis
- patellar flexion (inf > backward)
- patellar ext. (inf > forward)
Y axis
- medial tilting
- lateral tilting
Z axis (spinning motion of patella)
- medial rotation
- lateral rotation
patellofemoral joint stress
walking: 25-50% of bw
running: 5-6x of BW (from 25-50%)
***
- knee flexion increased > resultant force increased
- knee flexion decreased > resultant force decreased/lower
True/False:
Too much bending (deep squats) on the knee can result to excessive compression of the patella.
true
t/n: this is called “patellofemoral joint syndrome/stress”
patellar instability (frontal plane instability)
- frontal plane/lateral patellar instability VERY COMMON (motions: IR & ER)
- d/t: physiological valgus of the knee / high q angle (pulled lat. = displaced lat.)
- imbalance of forces (weak VMO) > instable lat
