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Knee and Tibia/Fibula
Knee: General Knowledge
Surgical Anatomy
Medial Layers of Knee
| 1. | What are the two components of layer I? | 1. | Sartorius and associated fascia Medial patellar retinaculum |
| 2. | What two structures lie between layers I and II? | 2. | Gracilis Semitendinosus |
| 3. | What are the four components of layer II? | 3. | Superficial medial collateral ligament (MCL) Posterior oblique ligament (POL) Medial patellofemoral ligament (MPFL) Semimembranosus |
| 4. | What are the two components of layer III? | 4. | Deep MCL Capsule |
Lateral Layers of Knee
| 5. | What are the three components of layer I? | 5. | Iliotibial (IT) band Biceps Fascia |
| 6. | What are the two components of layer II? | 6. | Patellar retinaculum Patellofemoral ligament |
| 7. | What are the four components of layer III? | 7. | Arcuate ligament Fabellofibular ligament Capsule Lateral collateral ligament (LCL) |
Posteromedial Corner
| 8. | What three structures make up the posteromedial corner? | 8. | Semimembranosus insertions POL (adductor tubercle origin) OPL (oblique popliteal ligament) |
| 9. | What is the function of the posteromedial corner? | 9. | Rotatory stability |
Posterolateral Corner (PLC)
| 10. | What five structures make up the posterolateral corner? | 10. | Popliteus Popliteofibular ligament Lateral capsule Arcuate ligament Fabellofibular ligament |
| 11. | What exam finding is suggestive of disrupted PLC? What if the posterior cruciate ligament (PCL) is also disrupted? | 11. | Asymmetric external rotation (ER) at 30 degrees knee flexion: isolated PLC injury Asymmetric ER at 30 and 90 degrees: PLC and PCL injuries |
Menisci
| 12. | What is the orientation of the superficial fibers? | 12. | Radial |
| 13. | What is the orientation of the deep fibers? | 13. | Predominantly circumferential Interspersed radial “tie fibers” |
| 14. | What type of cartilage makes up the meniscus? | 14. | Fibroelastic cartilage |
| 15. | What is the predominant collagen type present within the meniscus? | 15. | Predominantly type I collagen |
| 16. | What cell type makes up the meniscus? | 16. | Fibrochondrocytes |
| 17. | How is the meniscus innervated? Where is the meniscus especially well innervated? | 17. | Peripheral two thirds innervated with type I and II nerve endings Especially well innervated in the posterior horn (mechanoreceptors) |
| 18. | What vessels provide the meniscal blood supply? | 18. | Geniculates supply blood to peripheral one third |
| 19. | What percentage of force does the meniscus transmit in extension? What percentage is transmitted in flexion? | 19. | 50% in extension 90% in flexion |
| 20. | Is the medial or lateral meniscus more mobile? Why? Why is this clinically important? | 20. | Lateral meniscus is more mobile Because popliteus interrupts lateral meniscal attachment May contribute to more common medial tears |
| 21. | What is the classic magnetic resonance imaging (MRI) appearance of a displaced bucket-handle tear of the posterior horn of the medial meniscus? | 21. | Double PCL |
Meniscofemoral Ligaments
| 22. | Between what structures do the meniscofemoral ligaments run? | 22. | Posterior horn of lateral meniscus to medial femoral condyle with PCL |
| 23. | Which of the meniscofemoral ligaments is anterior? Which is posterior? | 23. | Humphrey’s (anterior) Wrisberg (posterior) |
Anterior Cruciate Ligament (ACL)
| 24. | What are the two main collagen types within the ACL and what is the relative proportions of each? | 24. | 90% type I 0% type II |
| 25. | What vessel supplies the ACL? What supplies the fat pad? | 25. | Middle geniculate supplies ACL Inferior geniculates supplies fat pad |
| 26. | What is the strength of the native ACL? | 26. | 2100 N |
| 27. | What are the two bundles of the ACL? | 27. | Anteromedial Posterolateral |
| 28. | At what flexion angle is the anteromedial bundle at maximum tension? | 28. | 60 degrees |
| 29. | At what flexion angle is the posterolateral bundle at maximum tension? | 29. | 15 degrees |
Posterior Cruciate Ligament (PCL)
| 30. | What are the two bundles of the PCL? | 30. | Anterolateral Posteromedial |
| 31. | At what flexion angle should the anterolateral bundle be tensioned intraoperatively? | 31. | 90 degrees |
| 32. | At what flexion angle should the posteromedial bundle be tensioned? | 32. | 30 degrees |
Collateral Ligaments
| 33. | How can the MCL or LCL be tested in isolation? What happens in extension? | 33. | Valgus or varus stress at 30 degrees flexion isolates the respective collateral ligament In extension, the PCL also contributes to stability |
| 34. | What is the better restraint against valgus stress: superficial or deep MCL? | 34. | Superficial |
Arterial Supply
| 35. | What two structures does the superior geniculate (lateral, medial branches) supply? | 35. | Patella PCL |
| 36. | What three structures does the middle geniculate supply? | 36. | ACL PCL Collaterals |
| 37. | What two structures does the inferior geniculate (lateral, medial branches) supply? | 37. | Menisci Fat pad |
| 38. | In what interval does the lateral branch of the superior geniculate lie? With what procedure is this branch most commonly at risk? | 38. | Femur/vastus lateralis At risk with lateral release |
| 39. | The inferior geniculate branch lies posterior to what anatomic landmark? | 39. | Posterior to LCL |
| 40. | Where does the tibial nutrient artery enter? | 40. | Below PCL insertion |
Patellar Anatomy
| 41. | What three facets make up the articular surface of the patella? | 41. | Lateral facet Medial facet Odd facet |
| 42. | What is the Wiberg classification? | 42. | Type I: medial and lateral facets are equal Types II and III: medial facet smaller than lateral Type IV (Jagerhut patella): no medial facet present |
| 43. | What are the two most likely sites of bony injury following lateral patellar dislocation? | 43. | Medial facet of patella Superior lateral condyle of femur |
Surgical Approach Pearls
| 44. | Over what structure is the medial knee approach centered? | 44. | Adductor tubercle |
| 45. | Over what structure is the lateral knee approach centered? What is the interval for dissection? | 45. | Centered over Gerdy’s tubercle Interval: iliotibial (IT) band/biceps femoris |
Other Key Facts
| 46. | How far distal does the knee capsule extend? Where is the most distal extent? | 46. | 15 mm distal extent Most distal extent is posterior to fibula |
| 47. | Within what tendon does the fabella lie? | 47. | Lateral gastrocnemius |
| 48. | The peroneal nerve lies at the posterior border of what structure? | 48. | Biceps femoris |
Biomechanics
| 49. | What is the screw home mechanism? | 49. | Femur internal rotation during the last 15 degrees of knee extension |
| 50. | Where does the lower extremity mechanical axis pass through the knee? | 50. | Medial to the medial tibial spine |
| 51. | Starting at vertical, what is the relationship of the mechanical and anatomic axes? | 51. | Mechanical axis lies in 3 degrees of valgus Anatomic axis is 9 degrees of valgus So, anatomic axis is 6 degrees of valgus relative to mechanical axis |
| 52. | How is the Q angle measured? | 52. | Anterior superior iliac spine (ASIS) to patella to tibial tubercle |
| 53. | What is the approximate normal value of the Q angle in extension? In flexion? | 53. | 15 degrees in extension 8 degrees in flexion |
| 54. | The highest joint reaction forces in the knee are experienced where? At what phase of gait? | 54. | Medially Stance phase |
| 55. | Where is the highest joint reaction force experienced in the patella? | 55. | Laterally |
Knee: Pathologic States
Meniscal Injuries and Repair
| 56. | What injury is associated with meniscal cyst development? | 56. | Horizontal cleavage tear of the lateral meniscus |
Baker’s Cyst
| 57. | In which interval can Baker’s cysts generally be found? | 57. | Between semimembranosus and medial gastrocnemius |
| 58. | What are the two conservative treatment options for Baker’s cyst? | 58. | Nonsteroidal antiinflammatory drugs (NSAIDs) Compression sleeve |
| 59. | If conservative treatment fails, what are the next steps? | 59. | MRI to evaluate for associated intraarticular pathology (e.g., meniscal tear) Operative treatment |
Discoid Meniscus
| 60. | How are discoid menisci classified? What are the three types? | 60. | Watanabe classification I: Incomplete coverage of lateral tibial plateau II: Complete coverage of lateral tibial plateau III: Wrisberg type |
| 61. | How does the posterior attachment differ between the types of discoid menisci? | 61. | Incomplete and complete discoid menisci have intact posterior meniscotibial ligaments Wrisberg variant has no meniscotibial ligament attachment to posterior horn |
| 62. | What is the clinical significance of this difference? | 62. | Incomplete and complete discoid menisci generally do not have abnormal motion and are asymptomatic unless torn Wrisberg discoid moves abnormally and is often symptomatic even without tear |
| 63. | What two radiographic features are suggestive of discoid meniscus? | 63. | Square lateral condyle Widened lateral joint space |
| 64. | What is the MRI appearance of a discoid meniscus? | 64. | Bow-tie appearance on more than two consecutive sagittal images |
| 65. | What are the two indications for surgery for discoid meniscus? | 65. | Symptomatic tears of the incomplete and complete discoid types Restoration of meniscal stability to a symptomatic Wrisberg type, even if not torn |
Meniscectomy
| 66. | Does medial or lateral partial meniscectomy lead to earlier degenerative changes? | 66. | Lateral |
| 67. | Three years after total meniscectomy, what percentage of patients has clinical osteoarthritis? | 67. | 20% |
| 68. | … radiographic osteoarthritis? | 68. | 70% |
| 69. | Total meniscectomy decreases the contact area by what amount? | 69. | 75% |
Meniscal Repair
| 70. | What is the “gold standard” approach? What is the suture technique? Why? | 70. | Inside-out Vertical mattress Highest number of circumferential fibers captured |
| 71. | What structure is at risk medially? How can injury be prevented? | 71. | Saphenous nerve Identify and retract nerve and infrapatellar branch before tying sutures |
| 72. | What structure is at risk laterally? How can injury be prevented? | 72. | Peroneal nerve Prevent by placing sutures anterior to biceps |
| 73. | What are the three general criteria for meniscal tears that do not need repair? | 73. | Longitudinal tear <8 mm in length that cannot be displaced >3 mm Stable partial tear Shallow radial tear <3 mm in depth |
| 74. | What are the six general indications for meniscal repair? | 74. | Complete longitudinal tear >10 mm length Tear within peripheral one third of the meniscus or within 3 to 4 mm of meniscocapsular junction Unstable tear that can be displaced by probing Tear without secondary degeneration or deformity Tear in an active patient Tear identified during ligament stabilization procedure |
| 75. | What four factors have been proven to enhance meniscal repair? | 75. | Trephination Synovial rasping Fibrin clot Hyaluronic acid |
| 76. | Does immobilization improve meniscal repair outcomes? | 76. | No |
| 77. | What is a possible complication of operative intervention in a patient with calcium pyrophosphate deposition disease? | 77. | May precipitate acute pseudogout attack |
Meniscal Transplantation
| 78. | What two factors must be present for meniscal transplantation to succeed? | 78. | Well-aligned knee Intact cruciate ligaments |
| 79. | What are the five contraindications to meniscal allograft transplantation? | 79. | Varus or valgus malalignment 2 to 4 degrees greater than contralateral knee Mechanical axis passes through the meniscus-deficient compartment Knee instability Age >50 Osteophyte formation Untreated Outerbridge class IV lesions |
Anterior Cruciate Ligament Injuries and Reconstruction
| 80. | What is the most common mechanism of ACL injury? | 80. | Noncontact pivot |
| 81. | What gender is most at risk for sustaining an ACL injury? | 81. | Female |
| 82. | How often does an acute bloody knee effusion correlate with a ruptured ACL? | 82. | 75% |
| 83. | What test is most sensitive on physical examination for ACL rupture? | 83. | Lachman test |
| 84. | What is a clinically significant KT-1000 (arthometry) difference side-to-side? | 84. | 3 mm |
| 85. | Once the ACL is disrupted, what is the primary restraint to anterior translation? | 85. | Meniscus |
| 86. | What plain radiographic finding is classically associated with an ACL injury? | 86. | Segond fracture |
| 87. | What is the MRI appearance of a bloody effusion? Nonbloody effusion? | 87. | Bloody: high T1, low T2 Non-bloody: low T1, high T2 |
Preoperative and Intraoperative Considerations
| 88. | What are the three preoperative requirements to minimize the risk of arthrofibrosis? | 88. | Full range of motion (ROM) No effusion Good quadriceps function |
| 89. | With a preoperative varus thrust, what procedure should be considered before ACL reconstruction? | 89. | High tibial osteotomy (HTO) |
| 90. | Of the graft options, which has the highest ultimate tensile load? | 90. | Quadrupled hamstring |
| 91. | What two hamstring tendons are used as graft for reconstruction? | 91. | Gracilis Semitendinosus |
| 92. | What nerve is at risk with hamstring harvest? | 92. | Sartorial branch of the saphenous nerve |
| 93. | What graft option has strength characteristics most similar to those of the native ACL? | 93. | Bone-patellar tendon-bone |
| 94. | What nerve is at risk with patellar tendon harvest? | 94. | Infrapatellar branch of saphenous nerve |
| 95. | In which direction is an intraoperative patellar fracture generally oriented? | 95. | Vertical |
| 96. | In which direction is a postoperative patella fracture generally oriented? | 96. | Horizontal |
| 97. | How can the strength of the graft be increased by about 30%? | 97. | Rotate 90 degrees |
| 98. | What is the benefit of preconditioning the graft? | 98. | Reduces stress relaxation by 50% |
| 99. | What are the two most reliable tibial tunnel landmarks? | 99. | Just anterior to PCL Native ACL footprint |
Postoperative Considerations
| 100. |
