Popliteus Muscle Overview

Aug 3, 2025

Overview

This lecture covers the anatomy, origins, insertions, innervation, and functions of the popliteus muscle, including its role in knee movement and meniscus protection.

Popliteus Muscle Anatomy

  • The popliteus is a deep muscle located at the back of the knee.
  • It is positioned beneath the gastrocnemius and just above the soleus on the posterior leg.
  • The popliteus is pronounced either "pop-lite-eus" or "pop-lit-eus".

Origin and Insertion

  • The popliteus originates from the lateral surface of the lateral femoral condyle of the femur.
  • Additional origins include the fibrous capsule of the knee joint and the lateral meniscus.
  • A fibrous band called the popliteofibular ligament connects the popliteus to the head of the fibula.
  • The muscle inserts onto the posterior surface of the tibia, just above the soleal line.

Innervation

  • The popliteus is innervated by the tibial nerve, which branches from the sciatic nerve.
  • Nerve roots contributing to this innervation are L5 and S1.

Actions of the Popliteus

  • Assists in unlocking the knee by laterally rotating the femur in a closed-chain position (foot on the ground).
  • In open-chain positions (foot off the ground), it assists with medial rotation of the tibia.
  • Pulls the lateral meniscus posteriorly during knee flexion, protecting it from damage.
  • Contributes minimally to knee flexion; not a primary mover.

Meniscus Protection and Mobility

  • The lateral meniscus is protected by the popliteus during knee flexion, making it less prone to injury than the medial meniscus.
  • The medial meniscus lacks an equivalent protecting muscle and relies on passive mechanisms.

Key Terms & Definitions

  • Popliteus β€” a small, deep muscle at the back of the knee joint.
  • Lateral femoral condyle β€” outer rounded projection at the end of the femur.
  • Popliteofibular ligament β€” fibrous band linking the popliteus to the fibula.
  • Soleal line β€” ridge on the posterior tibia marking the origin of the soleus muscle.
  • Tibial nerve β€” branch of the sciatic nerve that innervates the lower leg.
  • Closed-chain position β€” stance where the foot is fixed and weight-bearing.
  • Open-chain position β€” stance where the foot is off the ground and non-weight-bearing.
  • Lateral/medial meniscus β€” crescent-shaped cartilages in the knee for shock absorption.

Action Items / Next Steps

  • Review diagrams showing the popliteus’ origin, insertion, and relation to the meniscus.
  • Memorize the innervation and key functions of the popliteus for exams.