The Knee [2] Flashcards
What are the major bones and joints of the knee?
Bones:
* femur
* tibia
* fibula
* patella
Joints
* tibiofemoral
* tibiofibular
* patellofemoral
Describe the MCL and LCL; what do they protect against and any major attachments?
MCL: protects from valgus forces and attctcahes to medial meniscus and joint capsule (protects knee from going inwards)
LCL: protects aginst varus force and is not attached to lateral meniscus (protects knee from going away from the midline)
Bonus: the unhappy traid is a tear of the medial meniscus, MCL, and ACL
Describe the ACL and PCL
ACL:
* acts as a restraint against anterior translation and internal rotation of the tibia (provides 86% of restraint)
* 2 bundles: anteromedial and posterolateral
PCL:
* restraint against posterior translation of tibia
* strongest and thickest ligament in the knee
* no rotational component here
* stronger than ACL
What is the Posterior Lateral Corner and what does it do?
(PCL)
It aids in rotational stability of the knee and includes 3 main structures
1. LCL (lateral collateral ligament)
2. PFL (popliteal fibular ligament)
3. PTU (popliteus tendon unit)
Describe the 2 menisci
- medial: c shaped
- lateral: O shaped
both provide cushion and stability due to the deepening of the socket
What does the transverese meniscal ligament do?
limits translation and stabilizes the menisci.
* it connects the medial and lateral menisci
Describe the meniscofemoral ligaments
It limits the translation of the lateral meniscus
* Anterior (humfrey’s): bifurcates and crosses over and behind the PCL
* Posterior (wrisberg’s): crosses over the PCL
What do the coronary ligaments do?
They limit the translation of menisci
and surround the tibial plateaus like a “crown”
- described as sutures
What are the 4 muscles of the quadraceps?
- rectus femoris (bi-articular); origin is AIIS
- vastus medialis;
- vastus lateralis
- vastus intermedius
- The vastus’s all originate on the femur
- All 4 inset into the tibial tuberosity on the patellar tendon
- Action: all extend the knee + the rectus femorus also flexes the hip
What are the OIA’s for the semimembranosus, semitendinosus, and biceps femoris?
Semimembranosus:
* O: ischial tuberosity
* I: medial condyle of tibia
Semitendinosus
* O: ischial tuberosity
* pes anserine
Biceps femoris
* O: long head originates at ischial tuberosity
* O: short head originates at linea aspera
* I: fibular head
All of them have the action of flexing the knee EXCEPT the biceps femoris short head will extend the hip
What are the OIA’s for the tensor fascia latte, sartorius, gracilious, and gastrocnemius
Tensor Fascia Latte:
* O: illiac crest
* I: gurdy’s tubercle
* A: abduct hip and extend & flex knee
Sartorius:
* O: ASIS
* I: pesansrine
* A: flexes the knee
Gracilis:
* O: ischial ramus
* I: pesanserine
* A: knee flexion
Gastrocnemius:
* O: medial and lateral head of the medial and lateral femoral epicondyle
* I: calcaneus
* Knee flexion + plantar flexion
What is the purpose of the popliteus?
- unlocks screw home mechanism
- also action is to flex the tibia and internally rotate tibia
What are the movements of the knee? and the degrees
Flexion:
- normal = 135-140
Extension:
- normal = 0
- up to 10 hyperextended
Tibial rotation: when we invert/evert the ankle the tibia follows suit
- internal and external rotation
Paterllar movements
Explain the screw-home mechanism?
Where the knee is in full extension and the tibia rotates to lock us into place
* when we are standing upright; the quads dont have to work hard bc of this mechanism that holds us aligned and in place
* the popliteus is what unlocks this
What are the 3 motions of the patella?
- glide: L&R, Up&down
- tilt: L&R, Up&down
- rotate/spin: L&R
Lot of freedom for motion here
Explain the different types of patellar alignment?
Alta: patella is low-riding
Baja: patella is high riding
We have no control over this
* The Insall-saluati index measures the length of the patella to the length of the patellar tendon (it should be 1:1)
What are the types of tibiofemoral alignment?
- Genu valgum: knock-knees
- Genu varum: bow-legged (seen in equestrian and hockey)
- Genu recurvatum: hyperextension
To know, you should see what comes in contact first
How do you measure the Q-angle and what is typical for men and women?
use 3 points:
1. midpoint on patella
2. tibial tuberosity
3. ASIS
women = 20-25; which is wider than men=15-20
* wider angle is associated with genu valgum
What is the role of the patella?
- increase the moment arm
- decrease the friction between the quad and femur
What does compression force do on the patella?
In a closed kinetic chain patellar femoral compression increases force as knee flexion angle increases
* bc of the increased demand on the quads duing knee flexion
* the largest contact area is at 60-90 degrees of flexion
* different contact area depending on joint angle
as we go through knee flexion, quads lengthen (eccentric contraction)
- athletes with knee pain should avoid 60-90 degrees
If we have 40 degrees of kneed flexion where is patellar contact at?
If we have 60 degrees of flexion
- inside and outside of patella
- middle of patella
KNOW THE CHART/DIAGRAM on pg 11
Know patellofemoral joint stress at different angles.
Where is the most stress in closed vs open systems?
- closed: 90 degrees
- open: 0 degrees
the crossover is 45-50 degrees and we dont want to go past this point
What are the pathomechanics of the ACL?
- individual mechanics can lead to ACL injury (some people are predisposed)
- Most tears in acl are non-contact
- genu valgum increases the rislk (bc wider q angle)
ACL prevents anterior translation and rotation
