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