Lecture Notes on Ligaments and Muscles of the Knee and Leg

Ligaments

Collateral Ligaments

• LCL (Lateral Collateral Ligament)
  • Restricts varus deviation.
  • Attaches from lateral epicondyle of the femur to fibular head.
  • Pencil-like, making it easier to palpate.
• MCL (Medial Collateral Ligament)
  • Also known as tibial collateral ligament.
  • Restricts valgus deviation.
  • Attaches from medial epicondyle of the femur to medial condyle of the tibia.
  • Deep fibers attached to the medial meniscus.
  • Flat thickening of the joint capsule.

Cruciate Ligaments

• ACL (Anterior Cruciate Ligament)
  • Restricts tibia from sliding forward and femur from sliding back.
  • Attaches anterior on tibia to posterior on femur.
  • Slack in knee flexion, taut in full extension.
  • Pain experienced walking up stairs.
• PCL (Posterior Cruciate Ligament)
  • Opposite function to ACL.
  • Restricts tibia from sliding back on the femur and femur from sliding forward.
  • Attaches posterior on tibia to anterior on femur.
  • Slack in knee extension, taut in full flexion.
  • Pain experienced walking downstairs.

Coronary Ligaments

• Attach medial and lateral menisci to their respective tibial plateaus.

Knee Anatomy and Movements

Menisci

• Structure: C-shaped fibrocartilage plates attached to tibia.
• Function: Shock absorption, spreading synovial fluid, deepening articulation between tibia and femur.
• Medial Meniscus: Attached to MCL.
• Injuries: Audible popping/cracking, swelling indicates injury.

Knee Joints

• Tibiofemoral Joint
  • Movements include flexion, extension, and limited rotational movements.
  • Closed pack position in full extension; loose pack at 25-30° flexion.
• Patellofemoral Joint
  • Patella glides over femur.
  • Dislocation usually occurs laterally.
  • Lateral femoral condyle prevents excessive lateral tracking.

Windlass Mechanism

• Tightening of plantar fascia with toe extension, leading to foot supination.

Screw Home Mechanism

• Tibial lateral rotation locks knee in full extension, unlocked by popliteus during flexion.

Muscles of the Leg

Anterior Compartment

• Tibialis Anterior
  • Dorsiflexion and inversion.
• Extensor Hallucis Longus
  • Extends big toe, assists in dorsiflexion, inversion.
• Extensor Digitorum Longus
  • Dorsiflexion, eversion, extends toes.
• Peroneus Tertius
  • Weak dorsiflexion and eversion.

Lateral Compartment

• Peroneus Longus
  • Plantar flexion, eversion.
• Peroneus Brevis
  • Plantar flexion, eversion.

Superficial Posterior Compartment

• Gastrocnemius
  • Plantar flexion, weak knee flexion.
• Soleus
  • Plantar flexion.
• Plantaris
  • Weak plantar flexion and knee flexion.

Deep Posterior Compartment

• Tibialis Posterior
  • Plantar flexion, inversion.
• Flexor Hallucis Longus
  • Flexes big toe, assists in plantar flexion.
• Flexor Digitorum Longus
  • Flexes toes, assists in plantar flexion.

Intrinsic Muscles of the Foot

• Extensor Digitorum Brevis
  • Extends toes, located dorsally.

General Information

• Muscles share common functions, nerve and blood supply.
• Anterior compartment muscles dorsiflex; others contribute to plantar flexion depending on malleolus position.
• Notes on tendons and retinacula: Prevent bowing, provide lubrication.