1. KNEE

2. Tibiofemoral Joint Modified hinge joint. Articulating surfaces:
Femoral condyles:
Convex and asymmetric.
Medial condyle is larger than the lateral.
Condyles are separated anteriorly by patellar groove.
Condyles are separated posteriorly by intercondylar fossa.

3. Tibiofemoral Joint Articulating surfaces: Tibial plateaus:
Concave and asymmetric.
Articular surface of medial plateau is 50% larger than that of lateral.
Separated by intercondylar tubercles.

4. Menisci Wedge-shaped fibrocartilage discs. Ends of menisci = horns:
Attached to intercondylar tubercles.
Coronary ligaments:
Attach menisci to rims of plateaus.
Anterior transverse ligament:
Joins menisci and allows them to move together.

5. Menisci Medial meniscus: Larger of the two. More securely attached.
Also attached to medial collateral ligament and to semimembranosus muscle.
More often injured than lateral.

6. Menisci Lateral meniscus: Attached to posterior cruciate ligament:
Via meniscofemoral ligament.
Attached to popliteus muscle.

7. Menisci Functions: Enhance stability of knee: Distribute weight.
Deepen articular surfaces.
Distribute weight.
Reduce friction between articular surfaces.

8. Menisci Movement: Medial meniscus moves posteriorly during flexion:
Due to tension in semimembranosus muscle.
Medial meniscus drawn forward during extension:
Due to tension in anterior capsular fibers.

9. Menisci Movement: Lateral meniscus moves posteriorly during flexion:
Drawn by tension in popliteal expansion.
Distorts more than medial meniscus.

10. Joint Capsule Large and lax. Deficient on lateral condyle:
For passage of popliteal tendon.
Anterior wall replaced by quadriceps tendon.
Excludes cruciate ligaments.
Commonly communicates with synovial bursae.

11. Bursae Suprapatellar:
Upward expansion of synovial cavity between femur and quadriceps muscle and tendon.
Proximally receives insertion of articularis genus muscle.

12. Bursae Prepatellar: Deep Infrapatellar:
Lies between superficial surface of patella and skin.
Deep Infrapatellar:
Lies between patellar ligament and tibia.

13. Bursae Subpopliteal. Gastrocnemius:
Under medial head of gastrocnemius.

14. Bursae Anserine bursa:
Between pes anserinus and tibial collateral ligament.
Note: pes anserinus = combined tendons of semitendinosus, gracilis, and sartorius.

15. Ligaments Collaterals: Medial (tibial): Attachments:
Medial femoral condyle.
Proximal tibia.
Partly continuous with adductor magnus tendon.
Attached to medial meniscus.
Distally separated from tibia by genicular vessels and nerves.

16. Ligaments Collaterals: Splits tendon of biceps femoris muscle.
Lateral (fibular):
Splits tendon of biceps femoris muscle.
Separated from lateral meniscus by popliteal tendon.

17. Ligaments Anterior cruciate: Weakest of cruciates.
Slack during flexion and taut during extension.
Prevents backward sliding of femur on tibia.
Prevents hyperextension of knee.

18. Ligaments Posterior cruciate:
Taut during flexion and slack during extension.
Prevents forward sliding of femur on tibia.
Prevents hyperflexion of knee.

19. Movements Flexion: Extension: First part (0 to 25 degrees):
Posterior rolling and spinning.
Anterior sliding of femoral condyles on tibial plateaus.
Extension:
First part:
Femoral condyles roll anteriorly and slide posteriorly.
Followed by rolling and spinning of condyles.

20. Movements Lateral-medial rotation of tibia:
At 90 degrees of knee flexion:
Up to 40 degrees of lateral rotation.
Up to 30 degrees of medial rotation.
Greater than 90 degrees of flexion:
Medial and lateral rotation ROM decreases.

21. Locking at Full Extension
During final few degrees of extension:
Femur rotates medially on tibia.
(Note that tibia would also rotate laterally on femur.)
Knee is brought into close-packed position:
Tibial tubercles are lodged in intercondylar notch.
Menisci are tightly interposed between tibial and femoral condyles.
= Locked or screw-home mechanism.
Popliteus laterally rotates femur for unlocking at beginning of knee flexion.

22. Axes Mechanical axis: Anatomic axis: Extends along femoral shaft.
From head of femur to head of talus.
Almost equivalent to anatomic axis of tibia.
Anatomic axis:
Extends along femoral shaft.

23. Axes Physiologic valgus:
Normal angle at knee where femoral and tibial axes meet:
170 – 175 degrees.

24. Axes Genu valgum: Lateral deviation of tibia. Less than 170 degrees.
Results in “knock knees.”

25. Axes Genu varum: Medial deviation of tibia. Greater than 170 degrees.
Results in “bow legs.”

26. Patellofemoral Joint During knee flexion/extension:
Central ridge of patella slides along central groove of femur.

27. Patellofemoral Joint During flexion: Tibia moves posteriorly.
Ligamentum patellae pulls patella distally and posteriorly:
Causes patella to remain firmly in apposition to femur.

28. Patellofemoral Joint During extension:
Patella is pulled proximally by quadriceps.
Vastus lateralis tends to pull patella laterally.
Vastus medialis oblique counteracts vastus lateralis.

29. Patellofemoral Joint Q-angle: Formed by vector of quadriceps:
From ASIS to middle of patella.
And vector of pull of ligamentum patellae:
From tibial tubercle to middle of patella.
15 degrees.