Clinical Biomechanics Of Knee Flashcards
What joints make up the knee joint?
Tibiofemoral
Patellofemoral
Superior tibiofibular (ankle movement over knee movement)
What plane does the Tibiofemoral joint prevent motion in?
Frontal plane
What are the 2 degrees of freedom of the Tibiofemoral joint?
Flexion/Extension
Medial and lateral rotation
What are the convex/concave parts in the Tibiofemoral joint?
Tibia- concave
Femur- convex
What is the difference between the medial and lateral tibial Condyle?
Medial Condyle is 50% larger with articular cartilage 3x thicker
Where does the menisci attach?
Tibial plateau (between lateral and medial tibial Condyles)
What is the function of the menisci?
Increases stability
Increases contact area
Decreases friction
Enhances proprioception
What does the menisci provide to the joint?
Lubrication and nutrients
What does the menisci transmit?
50-60% of all forces placed on the knee
What is the shape of the medial and lateral meniscus?
Medial- C shaped
Lateral- O shaped
What is the attachment of the medial and lateral meniscus?
Medial- firm attachment to deep layers of MCL
Lateral- loose attachment to lateral capsule
What is the thickness of the medial and lateral meniscus?
Medial- thick posteriorly
Lateral- uniform thickness
What do the medial and lateral meniscus have in common with thickness?
Thicker on periphery, thinner along inner margin
What are the implications if you lose your menisci?
Shock absorption reduced by 20%
Increases load on femur by 2x and on tibial Condyles by 6-7x
How long is the menisci well vascularized?
Age 11
What is the periphery of the menisci well vascularized by?
Joint capsules and synovial membranes
What is the periphery of the menisci known as?
Red-Red zone (more blood flow, heals better)
What is the middle of the menisci known as?
Red-white (pink) zone (some blood flow)
What is the inner of the menisci known as?
White-White zone (poor blood flow, heals worse)
What is another factor that relates to healing of the meniscus besides vascularization?
Complexity of the tear
What does the Tibiofemoral ligaments control?
Hyperextension
Varus/valgus
Anterior/posterior displacement
Medial/lateral rotation
What does the MCL prevent?
Abduction (valgus) stress
What is the superficial layer of the MCL?
Thick, flat band (attaches 6 cm from joint line)
What is the deep layer of the MCL?
Continuation of capsule (attached to medial meniscus)
What does the MCL assist in?
Assists ACL to prevent anterior translation of tibia
What is injured more between the MCL and LCL?
MCL
Where is the LCL located?
Outside joint capsule (heals easier)
What does the LCL prevent?
Adduction (varus) stress
Where does the LCL attach?
Head of fibula
What has greater laxity between MCL and LCL?
LCL
What could an injury to the ACL also injure?
Medial meniscus
When are both the anteromedial and posterolateral major bundles of the ACL under tension?
Full extension
When is the posterolateral major bundle of the ACL under maximum tension?
0-30° of flexion
When is the anteromedial major bundle of the ACL under maximum tension?
45-60° of flexion
Where is most rotation available in the anteromedial and posterolateral major bundles of the ACL?
60-90° of flexion
Where does the ACL attach?
Lateral femoral Condyle to
Anterior intercondylar surface and anterior horn of medial meniscus
What does the ACL prevent in open chain?
Anterior tibial translation
What does the ACL prevent in closed chain?
Posterior femoral translation
What does the ACL assist to limit?
Hyperextension
Valgus forces
IR/ER
What could an injury to the PCL also injure?
Lateral and medial meniscus
Where does the PCL attach?
Medial femoral Condyle to
Posterior horns of medial and lateral meniscus
How much stronger is the PCL when compared to the ACL?
50% thicker and 2x stronger
What does the PCL prevent in open chain?
Posterior translation of tibia
What does the PCL prevent in closed chain?
Anterior translation of femur
What does the PCL assist to prevent?
Varus/valgus forces
IR/ER
When is the anterolateral bundle of the PCL under most tension?
Flexion
When is the posteromedial bundle of the PCL under most tension?
Extension
What type of joint is the Tibiofemoral joint?
Modified hinge synovial
How is the shaft of the femur aligned?
Slightly medially (creates normal valgus of 5-10°)
Why does the medial femoral Condyle extend distally further?
To accommodate and distribute weight bearing evenly
What is the Q angle?
Angle formed by line drawn from ASIS to mid patella and line from mid patella to tibial tuberosity
What is the normal Q angle for males?
10-14°
What is the normal Q angle for females?
15-17°
What does it mean if you are over the average Q angle?
Valgum
What does it mean if you are under the average Q angle?
Varum
What is the contact pressure of Patellofemoral joint in full knee extension?
0
When is there the most contact pressure in the Patellofemoral joint?
90° of flexion
What is the normal ROM for knee extension?
5-10°
What is the normal ROM for knee flexion?
130-140°
What is an angle of >15° of knee extension considered?
Genu recurvatum
What is the screw home mechanism in open chain extension?
Tibia externally rotates on fixed femur
What is the screw home mechanism in closed chain extension?
Femur internally rotates on fixed tibia
What unlocks the knee from the screw home mechanism?
Contraction of politeus
How does the knee move in open chain?
Concave moving on convex (roll and glide in same direction)
What is extension accompanied by in open chain?
Anterior tibial glide
What is flexion accompanied by in open chain?
Posterior tibial glide
How does the knee move in closed chain?
Convex on concave (roll and glide in opposite directions)
What is extension accompanied by in closed chain?
Posterior femoral glide
What is flexion accompanied by in closed chain?
Anterior femoral glide
What is closed packed?
Maximum area of surface contact occurs (perfect fit)
Joint is compressed
What is open (loose) packed?
Where you can assess best amount of movement
What is the significance in closed packed position?
Load on static stabilizers
What is the significance in open packed position?
Load of dynamic stabilizers (decreases friction)
When is the knee in closed packed?
Full extension and ER
When is the knee in an open packed position?
25° flexion
What is flexion needed for gait?
60-70°
What is flexion needed for on/off toilet?
75°
What is flexion needed for stair climbing?
70-80°
What is flexion needed for sit/rise from chair?
90°
What is flexion needed for in/out of bath?
90°
What is flexion needed for advanced function?
115°
What percentage of knee osteoarthritis contributes to genetic factors?
40-65%
What is clinical classification for OA of knee?
Knee pain plus 3 of following 6
Age > 50
Morning stiffness < 30 min
Crepitus
Tenderness
Bony enlargement
No palpable warmth
What does replacing the patella during a TKA result in?
Longer healing time
What is rehab for a TKA 1-2 weeks post?
0-90° flexion (don’t open incision)
What is rehab for a TKA 3-6 weeks post?
115° of flexion
Increase strengthening
What is the Wells criteria?
Risk factors for DVT post surgery