Knee Joints

• General Knee Anatomy

  the knee joint is the largest + most complex joint in the body

  despite its single joint cavity, the knee consists of 3 joints in one

  
• The 3 Knee Joints

  femoropatellar joint - intemediate joint between the patella + lower end of the femur

  lateral + medial joints - (collectively known as the tibiofemoral joint) between the femoral condyles above + the C-shaped menisci of the tibia below
• Role of the Menisci in the Knee

  besides deepening the shallow tibial articular surfaces, the menisci help revent side-to-side rocking of the femur on the tibia + absorb shock transmitted to the knee joint

  however, the menisci r attached only at their outer margins + r freq torn free

  
• Tibiofemoral Joint

  the tibiofemoral joint acts primarily as a hinge, permitting flexion + extension

  However, stucturally it is a bicondylar joint

  some rotation is possible when the knee is partly flexed + when the knee is extending

  but when the knee is fully extended, side to side movements + rotation r strongly resisted by ligaments + the menisci

  
• Femoropatellar Joint

  the femoropatellar joint is a plane joint + the patella glides across the distal end of the femur during knee flexion

  
• Partial Closure of the Knee Cavity

  the knee joint is unique in that its joint cavity is only partially enclosed by a capsule

  the relatively thin articular capsule is present only on the sides + posterior aspects of the knee, where it covers the bulk of the femoral + tibial condyles

  
• 3 Ligaments from Patella to Tibia

  anteriorly, where the capsule is absent, 3 broad ligaments run from the patella to the tibia

  = patellar ligament flanked by the medial + lateral paetllar retinacula, which merge into the articular capsule on each side

  
• Patellar Ligament & Retinucala

  the patellar ligament + retinucula r continuations of the tendon of the bulky quadriceps muscle of the anterior thigh
• General Functions of the Joint Ligaments

  all 3 types of joint ligaments (extracapsular, capsular + intracapsular) stabilise + strengthen the capsule of the knee joint
• Capsular & Extracapsular Ligaments

  all of the capsular + extracapsular ligaments act to prevent hyperextension of the knee + r stretched tight when the knee is extended
• Extracapsular Fibular & Tibial Collateral Ligaments

  the extracapsular fibular + tibial collateral ligaments r critical in preventing lateral/medial rotation when the knee is extended

  the broad, flat tibial collateral ligament runs from the medial epicondyle of the femur to the medial condyle of the tibial shaft + is fused to the medial meniscus

  
• Intracapsular Cruciate Ligaments

  knee's intracapsular ligaments = cruciate ligaments cos they cross each other, forming an X in the notch between the femoral condyles

  
• Functions of Cruciate Ligaments

  they act as restraining straps to help prevent anterior-posterior displacemnt of the articular surfaces + to secure the articulating bones when we stand
• Anterior Cruciate Ligament

  the ACL attaches to the anterior intercondylar area of the tibia

  from there it passes posteriorly, laterally + upward to attach to the femur on the medial side of its lateral condyle

  
• Function of ACL

  this ligament prevents forward sliding of the tibia on the femur + checks hyperextension of the knee

  it is somewhat lax when the knee is flexed + taut when the knee is extended
• Posterior Cruciate Ligament

  the stronger PCL is attached to the posterior intercondylar area of the tibia + passes anteriorly, medially + superiorly to attach to the femur on the lateral side of the medial condyle

  
• Functions of the PCL

  this ligament prevents backward displacement of the tibia/forward sliding of the femur