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Chapter 6

Chapter 6. The Knee. Introduction. Little bony support Tibiofemoral and patellofemoral joints rely on soft tissue structures to control forces transmitted through the joints Femur and lower leg = body’s longest lever arms. Clinical Anatomy. Tibiofemoral joint – tibia, menisci, and femur

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Chapter 6

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  1. Chapter 6 The Knee

  2. Introduction • Little bony support • Tibiofemoral and patellofemoral joints rely on soft tissue structures to control forces transmitted through the joints • Femur and lower leg = body’s longest lever arms

  3. Clinical Anatomy • Tibiofemoral joint – tibia, menisci, and femur • Patellofemoral joint must also function properly • Bones & Bony Landmarks • Figure 6-1, pg 186, Figure 6-2, pg 187 • Femur • Linea aspera • Medial and lateral condyles • Medial and lateral epicondyles

  4. Clinical Anatomy • Tibia • Medial and lateral tibial plateaus • Tibial tuberosity • Patella • Fibular head • Proximal tibiofibular syndesmosis

  5. Articulations and Ligamentous Support • Double condyloid articulation • 2 planes of motion: flexion/extension and internal/external rotation • Accessory motions: valgus/varus and anterior/posterior glide

  6. Joint Capsule • Figure 6-3, pg 187 • Fibrous capsule surrounds circumference of knee jt • Medial, anterior, and lateral aspect • Capsule arises superior to femoral condyles and attaches distal to tibial plateau • Posterior aspect • Capsule arises from the posterior margins of femoral condyles above joint line and attaches to posterior tibial condyle • Reinforcement from ligaments and muscles

  7. Joint Capsule • Synovial capsule lines articular portions of fibrous joint capsule • Medially, anteriorly, and laterally • Surrounds condyles of femur and tibia • Posteriorly • Runs anteriorly along femur's intercondyler notch and tibia’s intercondyler eminences, excluding the cruciate ligaments

  8. Collateral Ligaments • Figures 6-4, pg 188 • MCL - Primary medial stabilizer of knee • Deep layer: thickening of joint capsule and attaches to medial meniscus • Superficial layer: separated from deep layer by a bursa, arises just below adductor tubercle and inserts 7-10 cm below joint line • Protects knee against valgus stress • Secondarily against external rotation of tibia and anterior translation of tibia on femur, especially in absence of intact ACL

  9. Collateral Ligaments • Figures 6-5, pg 188 • LCL • No attachment to meniscus or capsule • Arises from lateral femoral epicondyle and inserts on proximal aspect of fibular head • Protects knee against varus stress when knee is between full extension and 30o of flexion • Secondarily against internal and external rotation of tibia

  10. Cruciate Ligaments • ACL • Figures 6-6, pg 189 • Arises from anteromedial intercondyler eminence of tibia, travels posteriorly, passes lateral to PCL and inserts on medial wall of lateral femoral condyle • Stabilizes against: • Anterior translation of tibia on femur, internal and external rotation of tibia on femur, and hyperextension of tibiofemoral joint

  11. Cruciate Ligaments • ACL has two segments that change positions as the knee flexes, causing the ACL to wind upon itself • Anteromedial bundle • Posterolateral bundle • Figure 6-7, pg 189 • Strain placed on ACL • PROM vs. AROM vs. RROM

  12. Cruciate Ligaments • PCL • Arises from posterior aspect of tibia and takes a superior and anterior course, passing medially to ACL, and attaches to lateral portion of femur’s medial condyle • Stronger, wider than ACL; primary stabilizer of knee • Provides restraint against: • Posterior displacement of tibia on femur and external tibial rotation

  13. Cruciate Ligaments • Posterior support also from popliteus complex and posterior capsule • Full extension – popliteus, posterior capsule, and other joint structures • Midrange (40-120 degrees of flexion) – anterolateral bundle of PCL • Beyond 120 degrees of flexion – posteromedial bundle of PCL

  14. Arcuate Ligament Complex • Figure 6-9, page 190 • Arcuate ligament complex • Arcuate ligament, LCL, oblique popliteal ligament, popliteus tendon, & lateral head of gastrocnemius • Provides support to posterolateral joint capsule • Assists in controlling posterolateral rotary instability; injury to area results in increased external rotation of tibia on femur

  15. Proximal Tibiofibular Syndesmosis • More stable than distal syndesmosis • Superior anterior and posterior Tibiofibular ligaments • Anterior displacement is blocked by bony outcrop of tibia • Fibular instabilities tend to occur posteriorly, affecting peroneal nerve

  16. The Menisci • Fibrocartilaginous medial and lateral menisci • Menisci serve to: • Deepen articulations of knee joint; increasing load transmission over a greater percentage of surface • Improve lubrication for articulating surfaces • Provide shock absorption • Increase stability of joint

  17. The Menisci • Figure 6-10, page 191 • Wedged shaped, thick outer borders • Knee is more stable in weight bearing • Each menisci is divided into anterior, middle, and posterior thirds • Vascular vs. avascular zones • Medial (C-shaped) vs., lateral (O-shaped)

  18. The Menisci • Coronary ligament • Attaches menisci at their peripheries to the tibia • Transverse ligament • Joins anterior horns of each menisci • Patellomeniscal ligaments • Connects menisci to patella tendon • Ligament of Wrisberg and ligament of Humphrey

  19. The Menisci • Knee extension • Patellomeniscal ligaments pull lateral meniscus anteriorly, distorting its shape • Early flexion • Popliteus pulls lateral meniscus posteriorly • Later ROM • Meniscofemoral ligament pulls posterior horn medially and anteriorly

  20. Muscles of the Knee • Table 6-1, pages 192-193 • Primarily serve to flex and extend • Anterior muscles • Figure 6-11, page 191 • Posterior muscles • Figure 6-12, page 194 • Popliteal fossa, figure 6-13, page 195

  21. Muscles of the Knee • Pes Anserine muscle group • Iliotibial Band • Figure 6-14, page 195 • The Screw Home Mechanism • Unequal sizes of femoral condyles and the tightening of the cruciate ligaments as they wind upon themselves during flexion necessitates a locking mechanism as the knee nears its final degrees of extension

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