Ligaments of the Knee Flashcards
ACL PCL LCL PLC MCL Postmed corner
What is the function of the ACL?
- Prevents anterior translation of the tibia to the femur
Name the origin, insertion and structure of the ACL?
- Origin
- Lateral Femoral condyle
- Insertion
- Broad and irregular
- anterior between Intercondyle eminence of the tiba
- Structure
- 33mmx11mm in size
- 2 bundles
- anteromedial
-
Posteriolateral
- prevents pivot shifting of knee
- prevents internal tibial rotation w knee near extension
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What is the blood supply to the ACL?
- Middle geniculate artery
What is the ACL composed of and what is it biomechanical strengths?
- 90% type 1 Collagen
- 10% type 3 Collagen
Strength
- 2200N
Describe which bundles of the ACL are tight in flexion and extension?
- Anteromedial ACL =Tight in Flexion
- Posteriolateral ACL =Tight in Extension
What is the function of PCL?
- Prevents posterior translation of tibia relative to femur
- PCL and posterior lateral corner work to Resist Posterior translation and posterolateral rotatory instability
Describe the origin, insertion, and structure of the PCL?
- Origin
- Medial femoral condyle
- Insertion
- Tibial sulcus
- Structure
- 38x13mm in size
- 2 bundles
- anterolateral
- posteriomedial
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What ligaments originate from the posterior horn of the lateral meniscus and insert into the substance of the PCL?
- Ligament of Humphrey - Anterior to PCL
- Ligament of Wrisberg- Posterior to PCL
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What is the blood supply and strength of PCL?
- Middle Geniculate artery
- strength 2500N
Descibe what happens to the 2 bundle of the PCL in knee flexion & extension?
- Anterolateral bundle= tight in flexion
- Posteriomedial bundle= tight in extension
What is the function of LCL?
- provide support to varus angulation
- works in concert with MCL to provide restraint to axial rotation
What is the origin, insertion, path and structure of the LCL?
- origin
- Lateral femoral condyle POSTERIOR and SUPERIOR to insertion of POPLITEUS
- Path
- runs Superficial to POPLITEUS
- Insertion
- on the fibula Anterior to popliteofemoral ligament of the fibula
- caspule’s most distant extent is joust post to fibular
- Structure
- cord like
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Describe the biomechanics and strength of the LCL?
- Tight in extension
- Lax in flexion
- strength
- 750N
What is the function of the posterolateral corner?
- works synergistically with PCL to control EXTERNAL ROTATION and POSTERIOR Translation
What structures are involved in the posterolateral corner?
- LCL (295N)
- Popliteus muscle & tendon (680N)
- Poplteofibular ligament ( 229N)
- Lateral capsule
Variable
- arcuate ligament
- iliotibial track
- fabellofibular ligament
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What is the function of the MCL?
- To provide restraint to valgus angulation
- works in concert with the ACl to provide restraint to axial rotation
What is the origin, structure and biomechanics of the MCL?
- Origin
- medial femoral condyle to medial tibia extending down several cm
- Structure
- 2components
-
Superificial Portion (tibial collateral lig)
- just deep to gracilis and semitendinosis
- inserts into periosteum of prox tibia ( deep to pes anerinus)
- primarly stabliser to Valgus stress
- contributes 57%, 78% of medial stability at 5 and 25 degrees of flexion
-
Deep ( medial capsular lig)
- separated from superificial by bursa
- attaches to medial meniscus
- divides into menisofemoral and mensicotibial portions
- acts as secondary restraints to valgus stress at full extension
- Biomechanical
- 4000N
What is the function of the posteromedial corner?
- Important for rotatory stability
Describe the anatomy of the postermedial corner?
- Lies deep to MCL
- formed by
- semimembranosus
-
posterior oblique ligament
- resists tibial internal rotation in full extension
- oblique popliteal ligament
- posterior capsule
Describe the osseous anatomy of the patella?
- Post surface has 2 cartilaginous facets
- medial
- lateral
- for articulationw distal femur
Describe the anatomy of the distal femoral condyles?
- Form the intercondylar groove for articulation w patella
- diameter of lateral femoral condyle> medial femoral condyle
Describe the stability of the patella within the trochlear groove?
-
Dynamic stability
- Vastus medialis= medial restraint to lateral translation
- Vastus lateralis= lateral restraint to medial translation
- Static stability
- medial patellofemoral ligament (MPFL)
- femoral insertion origin between medial epicondyle and adductor tubercle
- primary restraint in 1st 20 degrees of flexion
What is the Q angle?
- angular differences between the quadriceps insertion and patella insertion create a Valgus angle
- first line from ASIS to middle of patella
- 2nd line form tibial tuberosity to middle of patella
- where they intersect = Q angle
- normal males 13 degrees, females 18 degrees
- creates a laterally directed force across the patellofemoral joint
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What is the function of the patella?
- To transmit tensile forces generated by the quadriceps to the patella tendon
- increases the lever arm of extensor mechanism
- A patellectomy decreases extension force by 30%
How far does the patella move during full flexion and at what angle is there max contact between patella and femur?
- 7mm
- 45 degrees
What is the best modality to measure articular cartilage of the knee ?
- MRI
- T2 sequence
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