Anatomy of the Knee - Dr Heaton

Anatomy of the Knee

Presenter: Dr. T. Heaton

Learning Objectives

• Recap the muscles of the thigh

• Understand the function of the bursae around the knee joint

• Describe the extra-capsular and intra-capsular ligaments of the knee

• Describe structures that pass through the popliteal region

• Understand the arrangement and osteological features of the bones in the knee joint

Muscles of the Thigh

Muscle Compartments

• Anterior Compartment

  • Psoas major

  • Iliacus

  • Rectus femoris

  • Vastus medialis

  • Vastus lateralis

  • Sartorius

• Medial Compartment

  • Obturator externus

  • Adductor magnus

  • Pectineus

  • Adductor longus

  • Adductor brevis

  • Gracilis

• Posterior Compartment

  • Semitendinosus

  • Biceps femoris (both long and short head)

  • Semimembranosus

Knee Joint Functionality

• The quadriceps tendon: runs anterior to the knee and is responsible for extending the knee.

• The posterior compartment muscles assist in flexing the knee.

Nerve Supply of the Lower Limb

• Femoral Nerve: Innervates Iliacus, Pectineus, Quadriceps, Sartorius

• Obturator Nerve: Supplies Obturator externus, Adductor brevis, Adductor longus, Gracilis

• Sciatic Nerve: Emerges in popliteal fossa; divides into Tibial Nerve and Common Peroneal Nerve

  • Tibial nerve passes between gastrocnemius heads

  • Common fibular nerve runs around the head of fibula

Popliteal Fossa Boundaries

• Superior:

  • Medial Side: Semimembranosus, Semitendinosus

  • Lateral Side: Biceps femoris

• Inferior:

  • Medial Side: Gastrocnemius

  • Lateral Side: Gastrocnemius and Plantaris

• Vasculature:

  • Artery: Popliteal artery (medial)

  • Vein: Popliteal vein (drains lesser saphenous)

The Knee Joint Overview

• Type: HINGE JOINT

• Movements: Flexion, Extension, small amount of rotation

Structure Components

• Ligaments

• Cartilage

• Menisci (fibrocartilage)

• Joint Capsule

Osteology of the Knee

• Comprises two articulations: Patellofemoral joint and Tibiofemoral joint

• All articulations share the same joint capsule

• Stability relies on ligaments and tendons

Tibia & Fibula Anatomy

• Tibia:

  • Contains proximal and distal tibiofibular joint

  • Features: medial/lateral condyles, tibial tuberosity, intercondylar eminence

• Fibula:

  • Comprised of head, neck, and shaft

Joint Capsule Structure

• Fibrous Membrane:

  • Encloses articular cavity, continuous with medial collateral ligament, not attached to lateral meniscus

  • Posteriorly strong (oblique popliteal ligament) preventing hyperextension

• Synovial Membrane:

  • Lined inside joint capsule

  • Produces synovial fluid for lubrication

  • Ligament injury can lead to swelling from synovial space rupture

Bursae in the Knee

• Extensions of the knee synovial cavity filled with synovial fluid

• Act as cushions against friction

• Key types: Prepatellar, Suprapatellar, Deep and Superficial Infrapatellar bursae

Articular Surfaces

• Weight-bearing articulation between femur and tibia

• Medial/lateral femoral condyles meet the tibial condyles as a hinge joint

• Patellar articulation allows quadriceps pull without tendon wear

Menisci

• C-shaped fibrocartilage attached to the tibial condyles

• Two types: medial and lateral

• Function: deepen tibial condyles' surface and cushion between femoral and tibial condyles

• Note: Medial meniscus is more prone to injury due to its attachment to the medial collateral ligament

Ligaments: Extracapsular vs Intracapsular

• Extracapsular Ligaments:

  • Medial (Tibial) Collateral Ligament

  • Lateral (Fibular) Collateral Ligament

  • Oblique popliteal ligament

  • Ligamentum patellae

• Cruciate Ligaments:

  • Anterior Cruciate Ligament (ACL) prevents forward movement of the tibia

  • Posterior Cruciate Ligament (PCL) prevents backward movement of the tibia

Drawer Tests for Ligaments

• Anterior Drawer Test (ACL): checks tibial movement against a fixed femur

• Posterior Drawer Test (PCL): evaluates backward movement of the tibia

Knee Joint Locking Mechanism

• While standing, the knee locks for stability:

  • Flatter condyles in extension provide stability

  • Femur medially rotates on tibia

  • Center of gravity is anterior to knee when extended

• Popliteus muscle is responsible for unlocking the knee

Blood Supply to the Knee

• Involves numerous arteries:

  • Key arteries:

    • Lateral circumflex femoral artery

    • Superior and inferior genicular arteries

Clinical Context: Deformities

• Varus vs Valgus Deformities: show abnormal knee alignment

  • Genu Valgum (Knock knees): distal tibia points laterally

  • Genu Varum: distal tibia points medially

Unhappy Triad Injury

• Caused by a lateral force to the knee, leading to:

  • Tear in the medial collateral ligament

  • Medial meniscus

  • ACL

Conclusion

Thank you! Any questions?