Gastrocnemius, Soleus, and Popliteus Muscle and Knee Anatomy

Introduction

• Focus on muscles: gastrocnemius, soleus, popliteus, and their relation to the knee.
• Importance of understanding knee anatomy and associated ligaments due to common injuries.

Muscle Overview

• Gastrocnemius:

  • Two-headed muscle
  • Attaches to femur, forms part of the Achilles tendon.
  • Function: plantar flexion of the foot and flexion of the knee (not primary).

• Soleus:

  • One-joint muscle, acts solely at the ankle.
  • Positioned beneath the gastrocnemius, important for plantar flexion.

• Popliteus:

  • Originates from the femur, inserts into the tibia.
  • Function: unlocks the knee by rotating the femur on the tibia.

• Plantaris:

  • Similar to palmaris longus in the arm, can be absent in some people.
  • Weak plantar flexor, serves as a potential donor for tendon grafts.

Knee Anatomy

• Fibula & Tibia Relationship:

  • Fibula is lateral; tibia is the major weight-bearing bone.
  • Fractures of the fibula often allow mobility; tibial fractures result in non-weight bearing.

• Condyles:

  • Condyle: bone protuberance at joints (femoral and tibial).
  • Medial and lateral condyles on the tibia articulate with femur but not with fibula.

• Patella:

  • Bone with a base and apex; involved in knee joint mechanics.
  • The articulation surface with the femur is smooth articular cartilage, subject to wear.

Joint Mechanics

• Knee Joint Forces:

  • Patellar compression forces are significant during movements like squatting.
  • Fractures can occur from excessive stress; awareness of injury mechanics is crucial.

• Ligaments:

  • Cruciate Ligaments: ACL (prevents forward tibial translation) and PCL (prevents backward tibial translation).
  • Collateral Ligaments: LCL (lateral, outside the capsule) and MCL (medial, inside the capsule).
  • Sprains can affect adjacent structures like the meniscus.

Meniscus and Bursae

• Meniscus:

  • Two types: medial and lateral, providing cushioning and stability.
  • Meniscal tears often require partial resection instead of complete removal.

• Bursae:

  • Fluid-filled sacs reduce friction; conditions like prepatellar bursitis can cause swelling.
  • Baker's cysts can occur due to fluid accumulation in the knee joint.

Interosseous Membrane

• Connects tibia and fibula, crucial for stability and can impact injury outcomes.

Movement and Function

• Plantar Flexion vs. Dorsiflexion:
  • Plantar flexion: pointing toes away; dorsiflexion: pointing toes towards head.
  • Knowledge of these motions and their associated muscles is essential for anatomy understanding.

Additional Notes

• Knee Injuries:

  • Awareness of common knee pathologies and their implications for movement and treatment.

• Therapeutic Considerations:

  • Understanding of muscle actions and joint mechanics aids in injury prevention and rehabilitation strategies.

Conclusion

• Summary of important anatomical and functional aspects of the knee, its muscles, ligaments, and potential injury sites.
• Preparation for hands-on learning in class.