Topic 4 Flashcards
identify, classify and state the functions of the patella
Sesamoid bone Base, apex, articular facets Centred in intercondylar groove of femur Mechanical advantage for knee extension
describe the joint capsule of the knee
No complete capsule Deficient anteriorly on femur where quadriceps tendon is Deficient anteriorly on tibia where patella ligament attaches to tibial tuberosity Deficient posteriorly where tendon of popliteus emerges (posterior to lateral tibial condyle) Receives much additional ligamentous reinforcement
describe the synovial membrane in the knee joint
Lines the joint capsule Extensive and complex Anteriorly attaches to patella Posteriorly closes off intercondylar fossa Does not enclose the ACL or PCL Communicates with some bursa
what is knee retinacula
Medial & lateral patellar retinaculum Aponeurosis – flat tendon From vastus medialis & vastus lateralis Medial retinaculum blends with periosteum of tibia Medial patellofemoral ligament Adductor tubercle to vastus medialis onto superomedial patella Lateral retinaculum blends with iliotibial tract Some cross-over of fibres to over side
coming off the vastus lateralis and vastus medialis are the lateral and medial patella retinaculum - which are broad sheets connective tissue that sweep over the gap of the joint capsule. they compensate for the gap in the joint capsule.
the medial retinaculum blends with the periosteum of the tibia. We have an extra ligament called the patelloligament which prevents a lateral displacement of the patella.
lateral retinaculum blends with the iliotibial tract.
list the bursae in the knee joint
Pes anserine Suprapatellar Extends 6cm superior to patella! Infrapatellar prepatella
describe the fibular/lateral collateral
Fibular/Lateral collateral
ligament - extracapsular
Attaches:
Lateral femoral epicondyle
Lateral surface head of fibula
Limits:
Extension
Lateral rotation
Adduction or VARUS forces
describe the popliteofibular ligament
Popliteofibular ligament - extracapsular
Attaches:
Popliteus tendon
Apex of head of fibula
Limits:
Lateral rotation of the tibia
describe the patella ligament
Patella ligament - capsular
From patella to tibial tuberosity
Continuation of quadriceps
tendon
Receives the patellar retinacula
Function:
Mechanical advantage in knee
extension
describe the tibial medial collateral ligament
Tibial/Medial collateral ligament - capsular
Attaches: Medial femoral epicondyle Medial tibial condyle Medial tibial shaft Medial meniscus
Limits:
Extension
Medial rotation
Abduction or VALGUS forces
describe the oblique popliteal ligament
Oblique Popliteal - capsular Strengthens central posterior joint capsule Is an expansion of the tendon of semimembranosus Travels superolaterally to femur
describe the arcuate popliteal ligament
Arcuate Popliteal - capsular Strengthens inferolateral posterior joint capsule Is an expansion of the tendon of biceps femoris attachment Travels superomedially over popliteus
describe the anterolateral ligament
Anterolateral ligament - capsular Attaches lateral femoral condyle midway between anterolateral tubercle (Gerdy’s tubercle) & head of fibula Some sources consider it part of the ITB stabiliser for rotation of the tibia?
describe the ACL
ACL - intracapsular Attaches anterior intercondylar area of tibia posteromedial surface of lateral femoral condyle Extra-synovial Limits medial rotation anterior slide of tibia on femur 3 anteriors on this slide
describe the PCL
PCL - capsular Attaches posterior intercondylar area of tibia lateral surface of medial femoral condyle attaches to lateral meniscus Extra-synovial Limits medial rotation posterior slide of tibia on femur 3 posteriors on this slide
describe the posterior meniscofemoral ligament
Posterior meniscofemoral - capsular Connects lateral meniscus to PCL Secondary restraint to support PCL More in functional knee lecture
describe the lateral and medial meniscus
Crescent shaped wedges of
fibrocartilage, thicker at ‘edges’
Shock absorption
Increase congruence
Medial meniscus - Larger, C-shaped, less
mobile as more attachments
Lateral meniscus - Smaller, almost circular
describe the tibiofemoral joint
Tibiofemoral
Synovial
Condyloid (modified hinge)
Biaxial
Movements:
Flexion 140º
Extension 0º (hyperextension)
Internal/medial rotation 10º-20º if flexed
External/lateral rotation 30º-40º if flexed
describe the patellofemoral joint
Patellofemoral Patella surface of femur Articular surface of patella (facets) Synovial Plane
when is the knee in close packed position
full extension
factors contributing to stability at the hip
- articular fit - reasonable congruency
- acetabulum labrum - deepens socket and increases congruency
- strong capsule - reinforced by ligaments
- angle of inclination - increases contact area
- muscles being parallel to neck of femur.
what are factors contributing to mobility at the hip joint
- acetabulum labrum - provides increased surface area for femoral head.
- ball and socket joint - multiaxial
how does the knee unlock?
Popliteus “unlocks”
knee by medially
rotating tibia.
what is the functional significance the locking mechanism of the knee joint?
1. Important contributor to tibiofemoral joint stability in extension 2. “Close packed position” • No muscle effort required to maintain full knee extension • Stable joint position: Maximum contact between joint surfaces, tibial tubercles lodged in the intercondylar notch, ligaments tense • BUT also uncomfortable, not the preferred resting position of the joint
what are the factors contributing to stability at the knee?
- STATIC: combination of non contractile and
bony elements
e.g. menisci, ligaments, capsule, articular cartilage,
ITB - DYNAMIC: muscles acting on or across the
knee joint
e.g. quadriceps, hamstrings, sartorius, TFL, gracilis,
gastrocnemius, popliteus, ITB
describe the menisci as a factor contributing to the stability
Static: Menisci
• Due to their complex anatomy, the menisci serve a variety of
biomechanical functions such as:
1. withstand load bearing forces
2. increase contact area at the tibiofemoral joint reduces stress at
the joint surfaces
3. assist in movement of femoral condyles
4. assist in stabilising translatory movements
• Menisci occupy ~ 60% of contact area between femoral condyles and
tibial plateau
• Menisci transmit >50% total axial load applied to tibiofemoral joint.
what are the attachments of the medial and lateral menisci
attachments of medial meniscus: • medial collateral lig • anterior and posterior cruciate ligs • semimembranosus
attachments of lateral meniscus: • posterior cruciate lig • medial femoral condyle via meniscofemoral ligs • popliteus
medial meniscus has greater ligamentous and capsular
restraint limited motion, contributor to greater
incidence of injury?
what are the movements of the menisci
Movements of the menisci:
- considerable distortion throughout range
- both move posteriorly during flexion (lateral > medial)
- keeps the menisci under the femoral condyles
- both active and passive elements contribute to movt.
describe the ligaments as a factor contributing to stability at the knee joint
Static: Ligaments
• combinations of structures provide stability at the knee –
no single structure in isolation
• concept of primary and secondary restraints
work together to provide stability
primary restraints – ‘workers’
secondary restraints – ‘helpers’
• if primary restraint is damaged, the secondary restraint
takes the load deterioration and increased joint
instability
describe the iliotibial band as a factor contributing to stability
Dynamic: Iliotibial band (ITB)
• part of the more extensive fascia lata
• from the fascia surrounding tensor fascia lata and
gluteus maximus and medius
• extends to the anterolateral tibia
• crosses both hip and knee
• has fibrous connections to biceps femoris, vastus
lateralis and the lateral patellar retinaculum – may
influence patella tracking through these connections
• consistently taut regardless of hip or knee position • falls in front of the axis of the knee in extension, slips behind the axis in flexion (and is more prominent in knee flexion) • affords some lateral joint stability particularly in flexion • assists ACL in preventing anterior slide of tibia on femur
describe the quadrate femoris as a factor contributing the stability of the knee joint
major extensor of knee • all parts of quadriceps femoris work throughout the range of knee extension stabilises the patella within trochlear groove • greatest force needs to be developed at the end of extension range – final 15degs greatest mechanical disadvantage
what are the functions of the vastus medialis oblique and longitudinal
Vastus medialis - longitudinal fibres (strongly
bound to VI proximally):
• knee extensor
Vastus medialis - oblique fibres:
• weak knee extensor
• prominent activation in last 40º of knee
extension
• medial patella stabiliser - prevents vastus
lateralis from laterally dislocating the patella
• increases the efficiency of vastus lateralis in
knee extension by realigning pull (required
force decreased by 13%) (Mirzabeigi et al,
1999)
what is the primary and secondary restraint for anterior tibial displacements
primary - ACL
secondary - medial collateral lig and iliotibial band
what is the primary and secondary restraint for posterior tibial displacement
primary - PCL
secondary - medial collateral, lateral collateral and oblique popliteal
what is the primary and secondary restraint for posterior tibial displacement
primary - PCL
secondary - medial collateral, lateral collateral and oblique popliteal
what is the primary and secondary restraint for abduction (valgus) at the knee
primary - medial collateral
secondary - ACL, PCL, oblique popliteal lig
what is the primary and secondary restraint for adduction (varus) at the knee
primary - not ligamentous
secondary - lateral collateral, posterolateral corner
what is the primary and secondary restraint for internal tibial rotation
primary - medial collateral and posteromedial corner
secondary - ACL and PCL
what is the primary and secondary restraint for external tibial rotation
posterolateral corner complex - which includes the lateral collateral and popliteal fibular ligament
