L19_The Posterior Thigh Knee and Popliteal Fossa Flashcards
Muscles of the posterior compartments of the thigh (hamstrings)
Describe the Biceps femoris muscle (Origin, insertion, function, innervation, blood supply)
Origin:
- > Long head: ischial tuberosity
- > Short head: Linea Aspera
Insertion: Head of the fibula
Function:
- > Long head: Hip extension, knee flexion
- > Short head: Knee flexion
Innervation:
- > Long head: tibial nerve (L5-S3)
- > Short head: Common fibular nerve (L4-S2)
Blood supply: the perforating arteries travelling through little openings in the Adductor Magnus muscle allowing them the travel from anterior to posterior wrapping around the back of the femur
Muscles of the posterior compartments of the thigh (hamstrings)
Describe the Semitendinosus muscle (Origin, insertion, function, innervation, blood supply)
Origin: Ischial tuberosity
Insertion: Anteromedial surface of proximal tibia via pes anserinus
Function: Hip extension, knee flexion
Innervation: tibial nerve (L5-S3)
Blood supply: the perforating arteries travelling through little openings in the Adductor Magnus muscle allowing them the travel from anterior to posterior wrapping around the back of the femur
Muscles of the posterior compartments of the thigh (hamstrings)
Describe the Semimembranosus muscle (Origin, insertion, function, innervation, blood supply)
Origin: Ischial tuberosity
Insertion: posterior medial tibial condyle
Function: Hip extension, knee flexion
Innervation: Tibial nerve (L5-S3)
Blood supply: the perforating arteries travelling through little openings in the Adductor Magnus muscle allowing them the travel from anterior to posterior wrapping around the back of the femur
Muscles of the posterior knee compartments of the thigh (hamstrings)
Describe the Popliteus muscle (Origin, insertion, function, innervation)
Origin: Lateral condyle of the femur
Insertion: posterior tibia above the soleal line
Function: knee flexion and unlocking of the knee
Innervation: Tibial nerve (L5-S3)
Describe the articulations of the knee and classification
Classification: modified synovial hinge joint (flexion/extension, slight medial/lateral rotation, locking/unlocking of the knee)
3 articulations:
- Femoral condyles with the tibial plateaus (2 one on the right and one on the left)
- Patella (sesamoid bone) with the patellar groove of the femur
Describe the extracapsular ligaments of the knee
The collateral (tibiofemoral) ligaments
Medial (tibial) collateral ligaments (MCL): Medial femoral epicondyle, proximal tibia, medial meniscus
- flat band
- attaches to the joint capsule
- firm attachment to the medial meniscus
- most commonly injured
Lateral (Fibular) collateral ligaments (LCL): Lateral femoral epicondyle, head of the fibula
- Completely outside of the joint capsule
- round - cord-like
They limit medial (LCL) and lateral (ACL) mvmt of the knee
Patellar Ligament: Goes over the patella and attaches to the tibial tuberosity
Describe the intracapsular ligaments of the knee
The cruciate Ligaments:
- Anterior Cruciate Ligament (ACL)
- Posterior Cruciate Ligament (PCL)
function -> Limit anterior (ACL) or posterior (PCL) translation of tibia relative to femur
- Posterior Meniscofemoral ligament
- Transverse ligament (connects minisci anteriorly)
Describe the Menisci (associated structure of the knee joint)
Medial meniscus:
- attachment to MCL
- Relatively immobile
- Crescent-shape (C-shaped)
Lateral meniscus:
- Fairly mobile
- Circular in shape (almost complete O)
Menisci: fibrocartilagenous discs that provide cushioning for the knee and enhance the congruity of the femoral and tibial condylar articulations
Function: limit the mobility
Describe the bursae and fat pads of the knee (associated structures of the knee)
They facilitate movement and reduce friction where tendons or muscles pass over bony prominences.
Can you explain the patellofemoral syndrome “Runner’s Knee”
Cause: Mal-alignment of the patella in the patellar (trochlear) groove)
Treatment: wear a brace: strengthening of quadriceps - particularly vastus medius to reverse proper tracking of the patella in the patellar groove
How to detect if the cruciate ligaments are damaged?
Use the Lachman’s anterior/posterior drawer test
anterior drawer sign:
- If there’s too much mvmt when pulling the tibia anteriorly
posterior drawer sign:
- If there’s too much mvmt when pushing the tibia posteriorly
Describe the “Screw-home mechanism”
When tibia is fixed:
- Medial rotation of the femur in locking of the knee (knee extension)
- Lateral rotation of the femur in unlocking the knee (knee flexion) -> popliteus muscle involved in unlocking the knee
Tell me the borders and the contents of the popliteal fossa
Borders:
- semimembranosus
- biceps femoris
- plantaris
- medial and lateral head of the gastrocnemius
- semitendinosus
Contents:
- Popliteal artery ( gives off superior and inferior medial/lateral genicular arteries to give blood supply to the knee)
- Popliteal vein (the small saphenous vein will merge with the popliteal vein at the popliteal fossa)
The trajectory of the artery and vein: Femoral a.v. -> through the adductor canal -> through the adductor hiatus -> popliteal a.v when passes behind the popliteal fossa
- The sciatic nerve splits into the tibial and common fibular nerve
- The tibial nerve gives off a cutaneous branch (medial sural cutaneous nerve) at the popliteal fossa
- The common fibular nerve gives off a cutaneous branch (lateral sural cutaneous nerve) at the popliteal fossa
Describe the vascular anastomosis around the knee and its clinical significance
The genicular anastomosis provides collateral circulation to supply the leg when the knee is fully flexed. When the knee suffers a popliteal aneurysm (when there’s a bulge in the artery), if the femoral artery has to be ligated surgically, blood can still reach the popliteal artery distal to the ligation via the genicular anastomosis.
