TIS

Chapter 7
Review for Advanced Orthopaedic Specialties - Anatomy
  1. Bony Anatomy
    1. Patella
      • largest sesamoid
      • thickest cartilage in the body
      • seven facets
      • increases moment arm of quads
    2. Femur
      • medial condyle larger and more symmetric
      • lateral condyle shorter
      • intercondylar notch higher on lateral side
    3. Tibia
      • relatively flat surfaces, sloping posteriorly
      • tibial spine central
      • medial plateau 50% larger and articular surface 3x thicker
      • ACL insertion just anterior to tibial spine
      • PCL arises from posterior tibia, distal to joint surface
    4. Clinical Implications:
      • patellectomy
      • disparity in condylar size contributes to screwhome mechanism
      • PCL attachment in TKR
      • changes following meniscectomy

  2. Anterior Anatomy
    1. Quadriceps
      • vastus lateralis (VL), vastus lateralis obliques (VLO)
      • astus intermedius
      • vastus medialis (VM), vastus medialis obliquis (VMO)
      • rectus femoris

    2. Clinical implications

  3. Intra-articular Anatomy
    1. Anterior cruciate ligament
      • femoral: posterior aspect of medial surface of LFC
      • tibial: fossa anterior and lateral to anterior tibial spine; some fibers attach to anteror attachment of LM; wider and stronger than fenioral attachment
      • femoral attachment posterior to axis of flexion while tibial attachment is anterior to flexion axis
      • twists on itself in a lateral spiral
      • anteromedial bundle (relative tibial attachment) femoral attachment from posterior and superior convexity; tibial attachment forms medial corner of tibial attachment
      • posterolateral bundle from anterior and inferior femoral attachment to posterior apex of triangle of tibial attachment
      • AM bundle more taut in flexion and PL bundle more taut in extension
      • actually a continuum of fascicles, with some portion taut throughout the entire range
      • middle geniculate artery

    2. Posterior cruciate ligament
      • invested in synovium, near longitudinal axis, medial to center of knee
      • strength to failure = 2000 N
      • femur: lateral portion of MFC in semicircle
      • tibia: depression on posterior tibial between plateus, 1 cm below articular margin
      • anterolateral band larger, taut in flexion
      • posteromedial band taut in extension
      • middle geniculate artery

    3. Menisci
      • 70% water
      • 30% dry weight
        • 70% collagen I (>90%) » II, III, IV, VI
        • 8-13% protein
        • 1% hexosamine
      • thick convex periphery, thin concave central margin
      • primary fiber orientation is circumferential
      • MM more firmly attached at peripheray via coronary ligament
      • LM more circular, covers more articular surface area, is more mobile and has meniscofemoral ligament attachments
      • vascular supply:

        10-30% MM, 10-25% LM
        0-3 mm vascular (red/red)
        3-5 mm gray zone (red/white)
        > 5 mm avascular (white/white)

    4. Anterior fat pad


    5. Plica
      • infrapatellar (ligamentum mucosum)
      • suprapatellar
      • medial

    6. Clinical implications
      • plica and fat pad syndrome are additional causes of anterior knee pain
      • meniscal vascular supply important in meniscal repairs and healing
      • posterior horn meniscal tear more common in ACL deficient patients

  4. Medial Anatomy
    1. Layer I
      • deep fascia: covers vastus medialis and MCL; extended to and joined by sartorius
      • pes anserine expansion
    2. Layer II
      • superficial MCL: parallel anterior and oblique posteriorly
      • patellofemoral ligament
      • joins layer I anterior to MCL forming patellar retinaculum
    3. Layer III
      • anterior 1/3 capsule (menisco-tibial, menisco-femoral)
      • middle 1/3 deep MCL
      • posterior 1/3 oblique popliteal ligament (OPL)
      • components and semimembranous insertion
        • direct to tibia, postero-medial corner
        • tibial attachment deep to superficial MCL
        Tendon sheath has 3 extensions:
        • OPL
        • expansion to superficial MCL
        • capsular attachment over medial meniscus

    4. Clinical significance
      • MCL primary restraint to valgus
      • provides additional restraint to anterior translation
      • menisco-tibial ligament and meniscal injuries
      • patellofemoral ligament & PF pain

  5. Lateral Anatomy
    1. Layer I
      • fascia lata, iliotibial band
      • biceps tendon
      • posterior fascia (over peroneal N)
      • anterior fascia to prepatellar bursa

    2. Layer II
      • quadriceps retinaculum anteriorly
      • incomplete posterior with two patellofemoral ligaments; extensions to lateral intermuscular septum, fabella, lateral meniscus and tibia
      • meniscopatellar ligament

    3. Layer III
      • deepest layer, part of joint capsule
      • single layer anteriorly
      • divides into two layers posterior to ITB

      Superficial: embryologically original capsule
      • lateral collateral ligament
      • fabellofibular ligament

      Deep: embryologically more recent development
      • coronary ligament
      • arcuate ligament
      • hiatus allows for popliteus tendon arcuate complex

    4. Clinical implications
      • LCL and deep structures limit varus, external rotation and posterior tibial translation at 30 degrees flexion
      • these are increased with further sectioning of the PCL
      • large increase in ER at 90 degrees suspicious of PCL

  6. Posterior Anatomy
    1. Superficial
      • semimembranous (stabilizes posterior capsule, posteromedial corner, posterior horn MM) and pes anserine medially
      • biceps tendon laterally (keeps LCL tight during knee flexion)
      • heads of gastrocnemius

    2. Deep
      PCL
      • see intra-articular anatomy

      Meniscofemoral ligaments
      • Wrisberg - posterior to PCL
      • Humphrey - anterior to PCL; can be quite large
      • posterior horn of LM to MFC
      • 70-100% have one or both
      • primary function is stabilization of meniscus

    3. Clinical implications
      • resists 95% of posterior displacement forces; max at 90 degrees flexion; no effect on varus or ER with PCL section alone
      • combined with PL corner can result in 15-25 mm posterior displacement
      • contact pressures in medial compartment increase with a peak at 60 degrees flexion
      • contact pressures increase at PF joint with peak at 90 degrees flexion
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