KNEE

KNEE

1. Largest lever arms in the body Femur and Tibia

2. Two joints

   • Bones: Tibia, patella and femur
   • Soft tissue: quadriceps, hamstrings, abductors, adductors, ACl PCL, LCL, MCL and mensici
   • Synovial joint
   • Patellofemoral and Tibiofemoral

3. Tibiofemoral Joint

   • Three types of motion:
     • Flex/Ext 0-140 Abd/Add 30 Int Rotation 45
   • Surface Joint Motion
     • Rotation takes place when there motion of the knee reaches the instantaneous centre if motion
       • A normal knee has an instant centre that is in the shape of a semi-circle
   • "Knee locking" or "screw home" mechanism
     • The tibiofemoral joint has a helical movement
       • The medial condyle is 1,7 cm longer than the lateral condyle
     • The tibia on the femur from a fully flexed position to a fully extended one.
     • The tibia descends and then ascends along the curves of the femoral condyles.
       • The tibia also rotates ext in this movement to make up the distance between the lateral condyle and tibia
         • This is known as int rotation as the foot and tibia remain stationary
     • An extended knee is unlocked by the popliteus muscle
     • The rotation of the knee can be assessed by a test : HELFET TEST

4. Functions of the cruciate ligaments

   • To prevent any shearing forces of the tibia across the femur
   • increase the stability of the knee during full extension
   • prevents hyperextension

5. Patellofemoral Joint

   • patella is a floating/sesamoid bone
     • Functions of this joint are
       • aiding knee extension y lengthening the lever of quads
       • providing better distribution of the compressive stresses of the femur
       • providing some protection of the joint when fully flexed

6. Functions of the Collateral Ligaments

   • Stability of the joint
   • Limit varus and valgus orientation

7. Coronal Alignment of the Knee

   • forces from the upper body and the foot are transmitted via the lower limbs
     • forces pass through the knee joint
   • An Anatomical axis is the axis along which the centre of the shafts of the tibia and femur
     • this is the axis of the femur which int and ext rot take place
     • Determines coxa vara and coxa valga