C H. 18 T HE K NEE

O BJECTIVES 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

B ONES Femur Medial and lateral condyles Tibia Tibia plateau Patella Largest sesamoid bone in the body

J OINTS 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%

C ARTILAGE 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

C OLLATERAL L IGAMENTS Medial collateral ligament (MCL) Attaches femur to tibia Lateral collateral ligament (LCL) Attaches femur to fibula Provides medial and lateral stability of the knee

C RUCIATE L IGAMENTS ‘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

M USCLES Quadriceps Vastus medialis Vastus lateralis Vastus intermedius Rectus femoris Powerful knee extensor Forms patella tendon which attaches to tibia at tibial tubercle

M USCLES Hamstrings Biceps femoris Semimembranosus Semitendinosus Activated during knee flexion Semitendinosus tendon used during ACL repair

M USCLES Pes Anserine-assist with knee flexion Sartorius Gracilis Semitendinosus Sartorius is the longest muscle in the body