• Complex joint:
    • No rotary motion in full extension.
    • Rotation enabled on flexion: up to 40 degree of rotation at 90° flexion (relaxes tendons)
    • Above Knee:
      • Vastus medialis - pulls patella medially (prevents lateral dislocation)
      • Vastus intermedius
      • Vastus lateralis
    • Medial:   (Aka Pes anserinus)
      • Sartorius
      • Gracilis
      • Semitendinosus
        • Tendon inserts on the oblique popliteal ligament. Adding posterior mobility to the ligament and medial meniscus during flexion.
    • Lateral:
      • Iliotibial tract
      • Tendon of biceps femoris.







    • Static Stabilizers (Ligaments).
      • MCL
        • Most commonly injured ligament.
        • Ligament is taught only in extension.
        • Limit forward glide of tibia on femur and limit rotation + abduction.
      • Collaterals are twice as effective in limiting rotational laxity as cruciate ligaments.
      • LCL
      • Posterior Capsule (prevents against anteromedial or anterolateral rotatory instability).
      • Cruciate ligaments:
        • Extend from intercondylar fossa of femur to intercondylar eminence of tibia.
        • Named on basis of their tibial attachment.
        • ACL
          • Prevents anterior displacement of tibia and excessive lateral mobility in flexion or extension.
          • Prevents hyperextension of knee.
          • ACL tears are rarely isolated, often associted with MCL tears.
          • Plentiful vascular supply.
          • When ruptures, hemarthrosis is almost always present!
        • PCL
          • Primary static knee stabilizer against rotation.
          • if ruptured, anteposterior and mediolateral instability can occur.
          • If ruptured, rarely isolated, usually associated with serious knee injuries.
    • Dynamic Stabilizers (Tendons/muscles)
      • Quadriceps tendon - dynamic stabilizer
        • Combination of tendons: vastus medialis, intermedialis, lateralis, and rectus femoris. 
        • Primary dynamic stabilizer of knee.
        • Attaches to patella and continues distally to tibial tubercle as patellar tendon.
      • Pes anserinus  (medial)
        • Conjoined tendons:
          • Gracilis, sartorius, and semitendinosus.
        • Stabilize against excessive rotary and valgus motion.
      • Semimembranosis (lateral)
        • Tendon has three extensions:
          • To posterior capsule (posterior oblique ligament), and tightens the capsule when stressed.
          • Posterior horn of medial meniscus (pulls posteriorly during flexion)
          • Medial tibial condyle - serving to flex and internally rotate the knee.
      • Other Lateral Stabilizers
        • 1. Iliotibial band - inserts lateral tibial condyle.
        • 2. Biceps femoris - lateral stability, knee flexion + external rotation.
        • 3. Popliteus muscle (posterir muscle inserting with a Y-shaped tendon called arcuate ligament, another limp inserts into posterior portion of lateral meniscus providing posterior mobility of lateral meniscus during flexion). 
      • KneeAnatomy5.png



    • Imaging:
      • AP
      • Lateral
      • Oblique (for tibial plateau and spines).
      • Otherviews:
        • Skyline (patellar view of supine patient with knees slightly flexed - beam down to feet).
          • See Patella relationship to femoral condyles.
        • Tunnel view  (patient lying prone, knee flexed to 40° from vertical)
          • See intercondylar notch.


    Ottawa Knee Rules


    Knee Xray series for knee injury plus any of these findings:                                                                                               



    1. Age >55y


    2. Isolated tenderness of patella.

      (no bone tenderness other than patella)


    3. Tenderness at head of fibula.


    4. Inability to flex to 90°


    5. Inability to bear weight both immediately and in ER (4 steps)

       (Transfer weight twice on each leg - limping allowed)



    Proximal Tibia Fractures

    • Fractures can be classified:
      • Intra-articular - "Condylar" (tibial plateau)
      • Extra-articular
        • Tibial spine
        • Tubercle
        • Subcondylar Regions
    • Classification:
      • Schatzker classification:
        • NOTE: tibial plateau fracture defined as  >4mm of inferior displacement.
        • Types I to III result of low energy trauma
        • Types IV to VI is high energy.
      • Type 1 - lateral condyle (aka splint fracture)
        • typically young patients because bone resists depression.
        • Suggests lateral menistal injury
      • Type II - lateral condyle + depression (aka split-depression)
        • Usually people >30yo bc subchondral bone is weaker.
      • Type III - Depression of lateral condyle.
        • Likely joint is unstable.
      • Type IV - Medial condyle (need higher force to fracture medial condyle)
        • High energy - high incidence of cruciate ligaments and popliteal artery injuries.
        • May be associated with # of intercondylar eminence.
      • Type V - Bicondylar
        • Possess varying articular depression and displacement.
        • Medial is usually split, and lateral is often depression (can be split)
      • Type VI - Bicondylar + fracture between diaphysis-metaphysis
        • High energy, often comminuted.
      • Screen shot 2013-09-02 at 11.23.47 PM.png
    • Mechanism:
      • Fall from height (20%)
      • Automobile-pedestrian where car bumper strikes over proximal tibia. (50%)
      • Lateral Tibial plateau #'s: abduction force on the leg.
      • Medial plateau: adduction
    • Imaging:
      • If clincally suspected but negative xrays: do CT!
      • Can do tibial plateau view (tibial plateau slopes down anatomically)
      • Look for avulsion fractures:
        • fibular head
        • femoral condyles
        • intercondylar eminence
      • Look for widened joint space (fracture of opposite condyle)
      • Look for knee effusion (occult fracture, peripheral meniscus, ACL/PCL, patellar dislocation)
        • Knee effusion appears as distance between two fat pads just superior to patella on lateral view
      • kneeEffusion.gif
    • Tx
      • Immobilize with long-leg posterior mold
      • Need operative fixation.
      • (CAN treat non-operatively, but very high degree of complications)
    • Complications:
      • Loss of ROM (prolongued immobilization)
      • Degenrative arthritis
      • Angular deformity

    Tibial Spine Fractures

    • Isolated uncommon: usually 8-14yo.



    • Atraumatic
    • Mid-ROM pain 45-90° flexion.
    • Sitting long periods.
    • Pain with walking down stairs.
    • Mechanism:  Young people that grow rapidly, associated with patellar maltracking.
    • Exam:
      • Can squat, but mid-ROM pain.
      • J-sign: sitting on bench - extend knee and it goes laterally.
      • Lean on Patella pushing it laterally --> pain.
      • "Clarke's Test" put hand on quad tendon.. push down against quads and ask patient to contract quad --> pain.


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