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Knee

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					                  Knee Joint
 What are the four bones that make up the knee
 joint?
            Femur      Tibia
             Fibula      Patella
A. Femur - the femur is the longest bone
   in the body.

B. Tibia - the tibia is the medial bone in the leg,
   bearing the weight of the lower leg
Bones of the Knee
            Bones of the Knee
C. Fibula - the fibula serves as attachment sites
   for knee joint structures and muscles. It does
   not articulate with the femur or patella. It is a
   non-weight bearing bone.
D. Patella - the patella is a sesamoid (free floating
   bone. It is embedded in the patellar tendon (or
   is it a ligament?). Not born with patellas.
   Protects structures beneath and changes angle
   of pull to create greater rotary force.
                  Knee Joint
   What is the classification of the knee joint?

The knee is classified as a ginglymus or hinge
joint. This is not entirely accurate, as the knee
does allow some rotation.
The knee is a fairly complex, and somewhat
unstable joint. It is often injured in athletics.
                  Knee Joint
 In addition to articular
  cartilage covering ends
  of bones, specialized
  cartilages – menisci.
 Attached to tibia and
  deepen tibial plateau.
 Enhance stability.
 Both thicker on outside
  border, taper to very
  thin on inside border.
Knee Joint
       Knee Joint Ligaments
A. Medial collateral ligament - prevents
   the knee from abduction or valgus forces.
   Often injured by blows to the lateral side of
   the knee.
B. Lateral collateral ligament - prevents
   the knee from adduction or varus forces.
   This ligament can be injured by blows to the
   medial side of the knee. Does not occur
   frequently.
      Knee Joint Ligaments
C. Anterior cruciate ligament - prevents the tibia
   from moving forward. The term cruciate means
   “cross. This ligament crosses with the posterior
   cruciate ligament between the tibia and femur.
  It attaches to the tibia anteriorly and the femur
   posteriorly. It helps maintain rotary stability.

This ligament is one of the most often injured in
sports, and is caused by hyperextension, and rotary
movements associated with planting and cutting.
       Knee Joint Ligaments
D. Posterior cruciate ligament - prevents the tibia
from moving posteriorly. It attaches anteriorly to
the femur and posteriorly to the tibia.

  This ligament in conjunction with the anterior
  cruciate helps maintain rotary stability. It is not
  as common of an injury as the anterior cruciate
  ligament. Injured more often in car accidents.
           Motions of the Knee
       What are the four motions that can occur
       in the knee joint?

A. Flexion - bending or decreasing the angle of the
   knee characterized by the heel moving toward
   the buttocks.
B. Extension - The opposite of flexion. Straightening
   or increasing the angle between the femur and
   the lower leg.
Knee Flexion
Knee Extension
          Motions of the knee
C. External rotation - rotary movement of the lower
   leg laterally away from the midline.
D. Internal rotation - Rotary movement of the lower
   leg medially toward the midline.
         Knee Joint Muscles
    Name the muscles that would be part of the
    quadriceps or knee extensor group:
Rectus femoris

Vastus lateralis
Vastus medialis
Vastus intermedialis
    Knee Joint Muscles
Name the muscles that would be considered
part of the hamstring or knee flexor group:

Semimembranosus          Semitendinosus
               Biceps femoris


What are the “other” knee joint muscles?
Popliteus, Gracilis, Sartorius, Gastronemius
     Quadriceps or knee extensor
     group
A. Vastus lateralis - vastus is the term for
   immense. These three muscles of the
   quadriceps group derive their name for
   their size and position.
    The vastus lateralis is the most lateral of
   the quadriceps group.
          Quadriceps

Rectus
Femoris




 Vasti
          Quadriceps group
    What are the actions of the vastus lateralis?
                Knee extension
    What are some good exercises for the vastus
    lateralis?
      Seated knee extension       Seated leg press
      Hip sled      Squats        Lunges
Note: The vastus lateralis can be involved in lateral
      patellar subluxation. It has a slight lateral pull,
      and if over developed, can cause problems.
        Quadriceps group
B. Vastus intermedius - this muscle is the middle
   of the three vastus muscles. It lies underneath
   the rectus femoris.

 What are the actions of the vastus intermedius?
              Knee extension
Exercises to strengthen the vastus intermedius
would be identical to those for the vastus lateralis
 To isolate the vastus muscles, knee extensions
 should be performed in the seated position.
         Quadriceps group
C. Vastus medialis - this is the most medial of the
   vastus muscles. It is often a target of needle
   biopsies when the quadriceps muscle is studied
   for exercise.
   What are the actions of the vastus medialis?
             Knee extension
Exercises to strengthen the vastus medialis are
similar to the other vastus muscles, but it is
emphasized in the last 10 to 20 degrees of extension.
         Quadriceps group
D. Rectus femoris - recall that the rectus femoris
   was studied with the hip muscles.

  What are the actions of the rectus femoris?

     Knee extension and hip flexion
                   Gluteus
                   Maximus

Semimembranosus
                  Biceps
                  Femoris
 Semitendinosus




Gastrocnemius
          Hamstring group
All of the muscles in the knee flexor/hamstring
group were covered in the hip joint.

 What are the actions of the biceps femoris?
      Hip extension Knee flexion
      External rotation of hip and knee.
  What are the actions of the semitendinosus?
    Hip extension Knee flexion
      Internal rotation of the hip and knee
         Hamstring group
 What are the actions of the semitendinosus?

      Hip extension    Knee flexion
      Internal rotation of the hip and knee
What are the actions of the semimembranosus?

      Hip extension    Knee flexion
      Internal rotation of the hip and knee
      “Another” Knee Muscle
Because of its action, the
popliteus is remembered
as “the key that unlocks
the knee”. It is the deepest
muscle at the back of the knee.
It is the only one-joint knee
flexor.
                Popliteus
What are the actions of the popliteus muscle?

 Flexion and internal rotation of the knee.

  It initiates knee flexion by medial rotation
  of the tibia to unlock the knee.
Exercises to strengthen the popliteus include
leg curls, and knee flexion with internal rotation.
       Knee Flexion Assistants
•   Sartorius: flexes knee & internally rotates
    lower leg
•   Gracilis: flexes knee & internally rotates
    lower leg
•   Gastrocnemius: flexes knee
•   Plantaris: short bellied muscle with long
    tendon insertion assists with knee flexion
    (missing in some humans)
           Plantaris




           Sartorius




Gracilis
Gastrocnemius
          Knee Joint Injuries

A. ACL rupture - most commonly damaged
  ligament of the knee. Many sports apply external
   and internal forces to knee. Often caused by some
   type of cutting, twisting or hyperextension.

  Unlike the MCL & PCL, the ACL does not have
  the capacity to heal. Once injured, it does not
  reconstitute as a functional entity.
ACL Tear
Normal ACL   Torn ACL
     Knee Joint Injuries
ACL injury rates are 4 to 8 times higher in
female athletes who take part in soccer,
basketball, track, and softball (compared to
baseball) than male athletes.
Sagittal plane landing mechanics may play
less of a role in gender-related ACL injury
than frontal and transverse plane
mechanics. Effect of fatigue on knee
valgus and internal rotation may have
more consequence on female than male.
     Numerous theories for gender ACL differences
                     including:
1. Women have a wider pelvis, increasing the
“Q” angle of the knee.
2. The place where the ACL passes through
   knee, intercondylar notch, of women is
   slightly smaller compared to men.
3. Lack of exposure to motor skills at early age
   leads to injuries at later age.
4. Hormones. Women in pre-ovulatory phase
have more ACL injuries presumably due to laxity.
Q Angle
          Knee Joint Injuries
B. Collateral ligament sprain - one of the most
   frequent knee injuries. Usually caused by
   blow to lateral knee. Deep fibers of medial
   collateral ligament attach to medial meniscus,
   so could disrupt meniscus too.
C. Meniscus tearing – frequently caused by
   planting foot during weight bearing while body
   undergoes rotation. Symptoms include pain,
   accompanied by locking or buckling of the
   joint.
            Knee Joint Injuries
D. Chondromalacia - affects the articulating
   cartilage on the interior surface of the patella.
   Possibly caused by incongruence between
   patella and femur. Symptoms include pain,
   swelling and a grating sensation.
E. Osgood Schlatter Disease - usually affects
   children and is caused by repeated usage of the
   knee extensors. This overuse results in a tearing
   or avulsion at the epiphysis of the tibial tuberosity.
   Symptoms include pain, swelling, hemorrhage.
Osgood
Schlatter
Disease

				
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