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 Patella Fibular head
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 ( 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 Transverse 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 Early flexion Later ROM
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