L6: Osteology of the Distal Femur, Patella, Tibia and Fibula, Functional anatomy of the knee, Disorders of the Knee Flashcards
Why does the shaft of the femur descend at an angle?
Brings the knee closer to the body’s centre of gravity
Increasing the stability
On the posterior side of the femur what is the roughened ridge called?
Linea Aspera
What does this posterior line start as on the medial side and the lateral side?
Medial side–> Pectineal line
Lateral side–> Gluteal Tuberosity (GMax insertion)
Distally what does the linear aspera become on the medial and lateral side?
Medial supracondylar line –> ends at adductor tubercle
Lateral supracondylar line–> ends at lateral femoral condyle
What is the name of the fossa formed by the widening of the medial and lateral supracondyle lines?
The popliteal fossa
What forms part of the knee articular joint?
Femur–> medial and lateral femoral condyle
Patella
Tibia
Which of the femoral condyles of the femur is bigger?
The medial condyle
Bears more weight
Centre of mass passes medial to knee joint
What is the name of the groove that the patella site in?
Trochlear (patellofemoral) groove
Anterior surface of distal femur
What do the inferior and posterior surface of the femoral condyles articulate with?
Menisci of the knee
Tibia
What stops the patella from moving laterally out of place when the leg bends or straightens? (patella tracking)
Prominent lateral femoral condyle
What type of bone is the patella classified as? Describe its basic shape?
Sesamoid bone
Triangular shape (upside down)
Base–> forms superior surface
Apex–> forms inferior surface
What is the attachment sites of the patella? What does it articulate with?
Superiorly attached to the quadriceps tendon
Inferiorly attached to the patella ligament (not tendon attaches bone to bone)–> inserts onto tibial tuberosity
Articulates with femur
Medial facet–> medial femoral condyle
Lateral facet–> lateral femoral condyle
What is the function of the patella?
Increase mechanical efficiency of Quadriceps muscle by 33-50%–> allows muscle to cross the anterior aspect of knee by acting as a falcrum
Protection–> protects anterior aspect of knee
Reduces frictional force between quads and femoral condyles during extension of the leg
What is the more common name for the tibia?
Shinbone
Describe the key features at the proximal end of the tibia?
Proximal tibia–> Widened–> Medial and lateral condyle
Forms tibial plateau–> articulates with femoral condyles
Intracondylar area–> Centre of area is intracondylar eminence
Either side–> medial and lateral intracondylar tubercles
Head of fibula–> proximal tibofibular joint
What is the importance of the intracondylar eminence and tubercles?
Attachement site for anterior cruciate ligament and menisci
Intracondylar tubercles articulate with intracondylar fossa (femur)
Posterior cruciate ligament attaches to the posterior edge of the intercondylar area
Describe the anatomy of the shaft of the tibia?
Prism shaped
- Anterior border–> palpable down anterior surface of the leg
- -> tibial tuberosity–> insertion of patella ligament
- Posterior border–> Soleal line–> origin of the soleus muscle, line extends inferomedially blending with medial edge of tibia
- Lateral border–> interosseous border–> interosseous membrane that binds the tibia and fibilar together
Describe the anatomy of the distal part of the tibia?
Widens to assist with weight bearing
Medial malleolus –> inferior bony projection, articulates with tarsal bone, forms part of ankle joint
Laterally–> fibular notch, fibula bound to tibia–> Distal/inferior tibiofibular joint
What is the main function of the fibular?
Attachment site for muscles
What are the three main articulations of the fibular?
Proximal tibiofibular joint–> articulates with lateral condyle of tibia
Distal tibiofibular joint–> articulates with fibular notch of tibia
Ankle joint–> articulates with talus bone of foot
Describe the anatomy of the fibular?
Proximal end–> enlarged head, facet for articulation with the lateral condyle of tibia
Shaft–> anterior, posterior and lateral surfaces, face respective compartment
Distal end–> continues inferiorly –> lateral malleolus
More prominent than medial malleolus of the tibia–> can be palpated
What is an important nerve associated with the fibular?
Common peroneal (fibular) nerve winds around posterior and lateral surface of neck of fibula–> vulnerable to damage in proximal fibular fracture
What type of joint is the knee joint?
Hinge-type synovial joint
Flexion and extension with small degree of medial and lateral rotation
Surfaces lined with hyaline cartilage
What bones form the knee joint? What are the main articulations?
Patella, femur and tibia
Tibiofemoral–> Medial and lateral condyles of femur, articulate with medial and lateral tibial condyles –> weightbearing joint
Patellofemoral–> Patella articulates with the femur at the trochlear (patellofemoral) groove
What is the neurovascular supply to the knee? What is an important clinical feature to be aware of?
Blood supply–> Genicular anastomoses–> supplied by genicular branches of the femoral and popliteal arteries
Clinical relevance–> If popliteal artery occluded–> genicular anastomoses dilate to maintain blood supply to leg
Nerve supply–> Hiltons law–> Nerves that cross the knee joint–> femoral, tibial and common peroneal (common fibular) nerves
How is the stability of the knee improved?
Tibial articular surface deepened–> menisci
Joint capsule–> support
Ligaments and surrounding muscles
What are the menisci and what are there functions?
Medial and lateral menisci
Fibrocartilagenous structures- C shaped- thicker peripherally than centrally
Deepen the articular surfaces of the tibia–> ↑ stability
Act as shock absorbers –> ↑ SA, dissipate forces
What are the attachment sites of the menisic?
Intracondylar eminence
Medial meniscus–> attached peripherally to medial (tibial) collateral ligament and joint capsule
Lateral meniscus–> small no attachment to lateral (tibial) collateral ligament –> fairly mobile, but attached to the medial femoral condyle by the posterior meniscofemoral ligament
Attached anteriorly by the transverse ligament of the knee
Peripheral rims loosely attached to the joint capsule and tibia by the coronary ligaments
What is the blood flow to the menisci?
Blood supply from periphery
Flow decreases with age–> avascular by adulthood–> impaired healing after trauma
What are the major ligaments in the knee?
Divided into three categories
Intracapsular ligaments: Cruciate ligaments
Extracapsular ligaments: Collateral ligaments, patella ligament
Strengthen the capsule: Oblique popliteal ligaments
What are the cruciate ligaments?
Anterior and posterior
Connect the femur to the tibia
Cross over
What is the proximal and distal attachment of the ACL? What is its function?
Hands in pocket
Proximal: Posterolateral aspect of the femoral intercondylar fossa (femur)
Distal: Anterior aspect of the intercondylar eminence of the tibia, and medial meniscus
Passes anteromedially
Function: resists anterior translation and medial rotation of tibia in relation to the femur
What is the proximal and distal attachment of the PCL? What is its function?
Proximal: Medial border and roof of intercondylar fossa (femur)
Distal: Posterior intercondylar area of tibia
Passes posteriolaterally
Function: Stabiliser of weight-bearing flexed knee
Prevents femur sliding off anterior edge of tibia
Why is the joint capsule deficient anteriorly?
Allows synovial membrane to extend beneath the patella
Suprapatella bursa–> small sac filled with synovial fluid
What strengthens the capsule on the medial, lateral and posterior surface?
Medial and lateral–> inferior fibres from the vastus medialis and lateralis (respectively)
Posteriorly–> Oblique popliteal ligament –> continuation of fibres from the semimembranosus tendon in superolateral direction from main insertion on the medial tibial condyle
What is the proximal and distal attachments of the patella ligament?
Proximal–> apex of patella
Distal–> tibial tuberosity
continuation of the quadriceps femoris tendon
What are the collateral ligaments?
Found on medial and lateral side of the knee
Stabilise knee
Prevent excessive medial and lateral angulation of the knee
What are the proximal and distal attachments of the collateral ligaments?
Medial collateral ligament–> wide flat ligament
Proximal–> Medial epicondyle of femur
Distal–> Medial condyle of tibia, and medial meniscus
Function–> resits lateral angulation of tibia on femur
Wider but weaker
Lateral collateral ligament–> Thinner and rounder
Proximal–> Lateral epicondyle of femur
Distal–> Depression on lateral surface of fibular head
Reinforced by the iliotibial tract
Function–> Resists medial angulation of tibia on femur
Weak in isolation, works as part of posterolateral corner with arcuate ligament and popliteus tendon
What is a bursae? What is the function
Small sac lined with synovial membrane Containing synovial fluid Cushion between the bones and tendon Reduce friction Allows free movement Either communicating or non communicating with the joint cavity
What are the names of the bursae within the knee? Where are they located?
6 Bursae
1) Suprapatella bursae –> extension of synovial cavity, between the quadraceps femoris muscle and femur
2) Prepatella bursae–> anterior surface of patella and skin
3) Superficial (or subcutaneous) infrapatella bursae–> between patella ligament and skin
4) Deep infrapatella bursae–> between tibia and patella ligament
5) Semimembranosus burase–> posterior, between semimembranous muscle and medial head of gastrocnemius
6) Subsartorial (pes anserinus) bursa–> between pes anserinus (common insertion of sartorius, gracillis and semitendinosus) and medial tibial condyle
What movements are possible at the knee joint? Which muscles makes these movements possible?
4 movements
1- Extension –> Quadriceps femoris (rectus femoris, vastus medialis, vastus lateralis, vastus intermedius)
2- Flexion –> Hamstrings (biceps femoris, semitendinousus, semimembranosus), gracilis, sartorius, popliteus, plantaris and gastrocnemius
3- Lateral (external) rotation–> biceps femoris
4- Medial (internal) rotation–> semimebranous, semitendinosus, gracilis, sartorius and popliteus
What happens when the knee is fully extended with the foot on the ground?
Knee locks 5 degree of medial (internal) rotation Cruciate ligaments tighten, lower limb becomes a solid column Weight bearing Thigh and leg muscles can relax briefly
How is the knee unlocked?
Popliteus contracts
Lateral (externral) rotation by 5 degrees
Allows the knee to flex
What is the Q angle?
The angle between the line of pull of the quadriceps tendon and the patellar ligament
Bigger hip= > Q angle more likely to have knee problems
What does the Q angle mean?
Means that during extension the patella wants to be displace laterally
What prevents this lateral displacement of the patella?
Two things:
- Deep trochlear (patellofemoral) groove with lateral femoral condyle more prominent anteriorly
- Vastus medialis obliquus–> inferior fibre of vastus medialis insert more distally and horizontally then the vastus lateralis–> contraction prevents displacement
What is the nerve innervation, general function and blood supply to the anterior compartment of the thigh?
Femoral nerve L2-L4
Generally extends the leg at the knee joint
Arterial supply: femoral artery- lateral and medial circumflex arteries and profunda fermoris branch
What are the muscles of the anterior thigh?
Pectineus
Sartorius
Quadriceps Femoris–> Rectus femoris, vastus medialis, vastus lateralis and vastus intermedius
Iliopsoas–> Psoas major and iliacus–> insert into anterior thigh
What is the origin and insertion of the iliopsoas muscle? What is the function? What is the innervation?
Psoas major and iliacus–> separate origins but common insertion and function hence considered iliopsoas
Origin
- Psoas major–> transverse process of T12- L5 and lateral margins of IVD
- Iliacus–> Iliac fossa of pelvis
Insertion
- Lesser trochanter (femur)
Function
- Flexes the lower limb at hip
- Lateral rotation of femur
Innervation
- Psoas major–> Anterior rami of L1-3
- Iliacus–> femoral nerve