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