Knee Part 2 Flashcards
Articulation Patellofemoral Joint
Convex patellar facets
Concave trochlear groove of femur
Patellofemoral Joint type
modified plane joint
Movements that occur patellofemoral joint
Superior/inferior and medial/lateral translation
Patellar stability is maintained by
bone, passive, and active structures
Tibial on femoral movement
Patellofemoral Joint
Patella slides relative to fixed trochlear groove of femur
femoral on Tibial movement
Patellofemoral Joint
- Trochlear groove of femur slides relative to the fixed patella
Patellofemoral joint problems may be related to weakness of
hip muscles
Patella acts as a ____ for the knee
increases quad power by _____ %
fulcrum
33-50
Patella embedded in the
tendon of the quadriceps femoris
Patella has _____ facets on articular surface
3
At full knee extension patella sits on
anterior surface of distal femur (femoral sulcus) against the suprapatellar fat pad
No bony contact with condyles
with knee flexed patella sits in ________ and contacts the ______
intercondylar notch, condyles
Patellar Tracking Flexion
InFeriorlyand medially
Patellar Tracking Extension
Superiorly and laterally
Abnormal patellar tracking can occur with an imbalance in the activity of the of the
vastus medialis obliquus (VMO) relative to the vastus lateralis (VL)
Most subluxations/dislocations of patella occur when the knee is
close to or fully extended, usually laterally secondary to the lateral pull of the quadriceps
- Path of Patella and Areas of Contact
- 135 deg knee flexion
Contacts the femur primarily in its superior pole
- Lateral facet and odd facet share articular contact with femur
at 135 deg of knee flexion the patella rests well below the trochlear groove, lodged in the
intercondylar notch of femur
Path of Patella and Areas of Contact
90 deg knee flexion
Primary contact region starts to migrate to its inferior pole
Path of Patella and Areas of Contact
90-60 deg knee flexion
Patella engaged within the trochlear groove of femur
Contact area between patella and femur is greatest (1/3 of total surface area contact)
Large level of joint compression secondary to quadriceps activation
Patellofemoral joint compressive forces across functional tasks:
- Walking on level surfaces:
1.3 x BW - SLR exercise:
2.6 x BW - Climbing stairs:
3.3 x BW - Squats:
7.8 x BW
Interrelated factors associated with joint compression
Patellofemoral joint
Knee flexion angle and quadriceps muscle force
Patellofemoral Joint Compressive stress is greatest at
60º-90º knee flexion
The net lateral pull exerted on the patella by the quadriceps is indicated by the
Q angle
The larger the Q-angle, the greater the
lateral muscle pull on the patella
Local Factors Across PFJ
Lateral Directed Forces
IT Band
Lateral patellofemoral ligaments
Bowstringing force on the patella
Lateral patellar retinacular fibers
Local Factors Across PFJ
Medial Directed Forces
Vastus medialis (oblique fibers)
Medial patellofemoral ligaments
medial patellar (retinacular fibers)
- Global Factors Across PFJ that can increase the Q-angle
Excessive knee valgus and knee ER
Increased Knee ER can occur as a combo of excessive
femur IR
Tibial ER
- Patella Alta and Baja
- Ratio of the distance between the
patella and the tibia to the length of the patella
Patella Alta –
increased distance
Patella Baja
decreased distance
Meniscus Function
Improve tibiofemoral congruence
Increase joint stability during motion
Help guide arthrokinematics of the knee
Help distribute WB forces (50-70% of load) and decreases pressure on articular cartilage in the knee joint
Help lubricate articular cartilage in the knee
Provides proprioception
WITHOUT Meniscus
Contact area would reduce by 50% (stress will increase in smaller area on the joint —> OA)
Load on femoral condyle doubled
Load on tibial condyle may increase 6-7 times
Friction increases by 20%
Medial Meniscus
C-shaped (oval)
Open toward intercondylar tubercles
Its external border attach to MCL and adjacent capsule
Lateral Meniscus
Circular shape
Its external border attach to lateral capsule
Popliteus tendon pass between LCL and the external border of lateral meniscus
Both menisci are connected anteriorly by
transverse ligament
Meniscus Attached to patella via
patellomeniscal ligaments (ant. capsular thickenings)
Meniscus attached to periphery by
coronary ligaments
Medial Meniscus is ______ mobile than lateral meniscus
less
more injury prone than lateral meniscus
What muscles attach to both menisci?
Quadriceps and semimembranosus
Popliteus attaches only to the
lateral meniscus
The meniscus is well vascularized during
1st year of life
once WB, begins to decrease
Meniscus
The peripheral (outer) 1/3 is
vascularized (“red zone”)
Mensicus
The central (inner) 2/3 is
avascular (white zone)
Central inner 2/3 of meniscus receives nourishment from
synovial fluid
Meniscus is well innervated with
free nerve endings and mechanoreceptors
With meniscus injuries, proprioceptive deficits may potentially occur
after injury
Most often cause of tears of the menisci
forceful axial rotation of femoral condyles plus a
valgus force over a flexed knee when weight-bearing
Surgery to remove meniscus can increase the contact pressure at the knee by 230% —> increase the risk of
stress-related osteoarthritis in the knee
Meniscus tears in the red zone
can be repaired
Meniscus tears in the white zone are usually
not repaired and sometimes require a meniscectomy
