CH. 18 THE KNEE

OBJECTIVES

Describe the functions of the knee Describe the ligament structure of the knee Explain the function of the patellofemoral

joint List and define various sports-related injuries

of the knee

BONES

Femur Medial and lateral

condyles Tibia

Tibia plateau Patella

Largest sesamoid bone in the body

JOINTS

Tibiofemoral joint is a hinge joint composed of a joint capsule and several ligaments Main motions are flexion and extension

Patellofemoral joint is the articulation between the patella and femur Gives greater mechanical advantage in knee

extension Increases quadriceps force by 33% to 50%

CARTILAGE

Articular cartilage covers ends of both tibia and femur

Menisci are located between femoral condyle and tibial plateau

Shock absorption, force distribution, improve stability

Synovial membrane and fluid

COLLATERAL LIGAMENTS

Medial collateral ligament (MCL) Attaches femur to

tibia Lateral collateral

ligament (LCL) Attaches femur to

fibula Provides medial and

lateral stability of the knee

CRUCIATE LIGAMENTS

‘Cruciate’ means cross

Anterior cruciate ligament (ACL) restricts anterior

translation of tibia Posterior cruciate

ligament (PCL) restricts posterior

translation of tibia Both control rotation

and help with stability

MUSCLES

Quadriceps Vastus medialis Vastus lateralis Vastus intermedius Rectus femoris

Powerful knee extensor

Forms patella tendon which attaches to tibia at tibial tubercle

MUSCLES

Hamstrings Biceps femoris Semimembranosus Semitendinosus

Activated during knee flexion

Semitendinosus tendon used during ACL repair

MUSCLES

Pes Anserine-assist with knee flexion Sartorius Gracilis Semitendinosus

Sartorius is the longest muscle in the body