The knee joint Flashcards
What joints make up the knee
- tibiofemoral
- patellofemoral
Tibiofemoral joint
technical knee joint (flex/ext)
Patellofemoral joint
articulation between patella and femur (gliding)
Functions of the knee joint
- transmits loads (that go from low extension or up from the ground)
- participates in motion
- aids in conservation of momentum (when you can’t efficiently walk you need to use other energy-using forces to gain motion)
ROM in sagittal plane of tibiofemoral joint
0 - 140 deg of flexion
ROM in transverse plane of tibiofemoral joint
full extension: 0 degrees (b/c lig and capsules should be tight
@ 90 deg knee flexion:
ER= 45 deg
IR = 30 deg
ROM in frontal plane of tibiofemoral joint
full extension = 0 deg
30 deg flexion = a few degrees only
Degrees of freedom of knee
TWO
- flex/ext in sagittal plane (predominant motion)
- IR/ER in transverse plane
Functional ROM of knee
0 - 117 degrees
range needed to do ADLs
Anatomy of tibiofemoral joint
- Double condyloid joint (one surface convex & one surface concave)
- 2 articulating surfaces: Medial & lateral
- Composed of two bones: femur & tibia
Anatomy of femur
- 2 condyles (articulating surfaces) separated by intercondylar fossa/notch
- notch becomes shallow –> PATELLAR GROOVE
Medial condyle of femur
- is 2/3 inches longer anterior-posterior
- extends further distally
Anatomy of tibia
- 2 condyles separated by intercondylar tubercles
- medial condyle = 50% larger
- 2 articular disks = menisci
Knee Menisci
- Dynamic (as opposed to static) structures
- assymmetric, wedge-shaped, fibrocartilagenous disk-like structures
area of menisci susceptible to tears
- “horns”
- open ends
vascularization of menisci is located
only in the periphery (poor)
Medial knee menisci
- semi-circular or c-shaped
- attaches to MCL
- more firmly attached
- less mobile – doesn’t give as much, therefore susceptible to injury
- MEDIAL = MORE likely to get hurt
Lateral Menisci
- 80% of a ring (O-shaped)
- more loosely attached to tibia - less susceptible to injury
Functions of menisci
1) distribute and absorb force (joint reaction)
2) enhance joint congruency
3) enhance arthrokinematics
4) aids in nutrition & lubrication
Meniscus tears - symptoms
- knee pain
- swelling
- tenderness
- popping/clicking
- limited motion (could be caused by structure interfering with gliding)
debridement
go in, take away pieces & clean it up
central meniscus tear
debride pieces torn
outer periphery meniscus tear
- debride if small tear
- repair if large tear
post operative treatment – debridement (meniscus)
- walking in 1 - 2 days
- full activity in 4 weeks
IMMEDIATE post op repair - meniscus
- knee immobilizer/brace
- flexion to 60 deg
- WBAT (weight bearing as tolerated) with knee locked in extension
1 month post op repair - meniscus
- continue with brace but not in extension
- ROM greater than 60 deg – let person go beyond 60
3 - 4 months post op repair - meniscus
return to activities
normal tibiofemoral alignment
185 - 190 degrees (slight valgus)
genu valgum
greater than 195 degrees
knock knee – knees stick together
increase compressive forces laterally
increase tensile forces medially
genu varum
less than 180 degrees
bow legged – knees spread apart
increase compressive forces medially
increase tensile forces laterally
Q angle
(quadriceps angle) – supine
- more clinical
- midpoint of patella to the tibial tuberoisty
normal q angle for males
less than 10 deg
normal q angle for females
less than 16 deg because females have a wider pelvis
pathological q angle
greater than 20 deg
causes the patella to track incorrectly
this is b/c the quads pull obliquely, causing patella to move laterally
AOR moves as knee moves through ROM…. this is typical of what type of motion???
curvilinear
spin
pure rotation (top) axis of rotation is fixed
glide/slide
skid
pure translation & no rotation
roll
ball/wheel
translation & rotation (curvilinear)
convex on stable concave surface
convex surface slides in opposite direction as motion of bony lever
concave on stable convex surface
concave surface slides in same direction as motion of bony lever
arthrokinematics of tibiofemoral joint in a standing position
flexed & stable tibia
0 to 25 degrees flexion of tibiofemoral joint (arthrokinematics)
primarily roll
beyond 25 degrees flexion of tibiofemoral joint (arthrokinematics)
anterior gliding of femur along with a roll = pure spin
in arthrokinematics of the tibiofemoral joint, why is there gliding with a roll???
(in greater than 25 deg flexion)
b/c gliding offsets the posterior displacement that would occur if rolling occurred alone
how does the meniscus contribute to the anterior glide of the tibiofemoral joint
b/c it is wedge shaped
screw-home/locking mechanism
tibial ER during the last 30 degrees of knee extension (this is b/c the medial condyle is longer)
greatest during the final 5 degrees
b/c of asymmetry of the femoral condyles
screw-home/locking mechanism with full knee extension
- tibial tubercles are lodged in intercondylar notch
- menisci tightly interposed between femur & tibia
- ligaments taut
passive stabilizers of the tibiofemoral joint
- joint capsule
- LCL
- MCL
- ACL
- PCL
- Iliotibial band
MCL
- posteromedial femur –> anterior tibia
- blends with capsule
- attaches to medial meniscus
- resists valgus stressers
LCL
lateral femur –> fibula head
- resists varus stressers
—note kick on the outside of the knee hurts the MCL bc the LCL compresses
ACL
posteromedial aspect of the lateral femoral condyle –> anterior intercondylar region of the tibia
- resists anterior tibial translation & IR of tibia
ACL injury
- flexion with femoral ER (ACL winds around PCL)
- flexion with femoral IR (ACL winds around lateral femoral condyle)
PCL
anterolateral surface of medial femoral condyle –> posterior intercondylar region of the tibia
- primary restraint to posterior tibial translation
- hyperextension is a common mechanism of injury
ITB
- fascia from TFL, gluteus maximus, & medius
- attaches to linea aspera of femur and lateral tubercle of tibia
- gives rise to iliopatellar band –> patella tracking problems
- reinforces anterolateral aspect of knee
*** tight ITB can cause patella to track incorrectly
patella functions:
- aids in extension by increasing moment arm
- —–***** this has the greatest effect at 20-40 degrees flexion
- allows for wider distribution of contact forces, causing decreased pressure and friction between quad tendon & femur
- protection
anatomy of patella
- triangular-shaped
- largest sesamoid bone
- least congruent joint
- 3 facets
with knee flexion the patella translates ________ & ___________
caudally & medial to lateral
full knee ________ —> sinks into femoral trochlea
flexion
patella also ____ (vertical axis) and ______ (anterior-posterior axis)
tilts; rotates
failure of patella to slide tilt or rotate properly can lead to:
- restricted patellar femoral ROM
- restricted knee ROM
- Patellar femoral tracking problems –> pain –> tissue damage
- patellar femoral instability –> subluxation & dislocation (usually laterally)
subluxation
partial dislocation
medial/lateral stabilizers of patella
medial patellar retinacula –> vastus medialis
lateral patellar retinacula –> vastus lateralis
superiorly/inferiorly
patellar tendon (ligament) quadriceps tendon
abnormal lateral forces on patella:
- vastus lateralis (pull too hard on knee)
- ITB (tight iliotibial band)
IN TERMS OF ABNORMAL FORCES ON PATELLA, anything that increases the obliquity (laterally) of the pull could cause
- excessive lateral compression
- subluxation &/or dislocation laterally
Excessive lateral oblique pull
- weakness of VMO
- excessive genu valgum (incr Q angle)
- excessive femoral anteversion
- tight lateral retinaculum/loose medial retinaculum
- tight ITB
- diminished height of lateral femoral lip
other factors affecting patella alignment & tracking
- status of gluteal muscles
- position of tibial tuberosity
- mechanics of feet
specific problems with vastus medialis obliqus
- barely reaches top of patella
- fibers run more vertical than oblique
extensors of knee
QUADICEPS
- vastus medialis (oblique and lateralis)
- vastus lateralis
- vastus intermedius
- recuts femoris
flexors of knee
hamstrings
- lateral (ER tibia) – biceps femoris (short/long)
- Medial (IR tibia) – semimembranosus, semitendinosus
popliteus
gracillis
sartorious
other musculature of knee
gastrocs
