A&P Bone Joint Dissection

 

You will be dissecting the knee joint of some animal (cat, beef, lamb, chicken etc…according to availability.)

Use the knee joint model, as well as pictures and diagrams available to you in lab and in your dissection packets for reference

 

Procedure:

  1. Prepare the small dissection tray.  Lay out paper toweling.
  2. Wear gloves for this dissection.
  3. Obtain a fresh bone specimen for observation.
  4. Do not make any cuts on this specimen as it will be used throughout the day by the other anatomy students.  This specimen is purely for observation only.
  5. Prepare the large dissection tray.  Lay out paper toweling.
  6. Open the cat dissection manual to the pages showing the muscles of the thigh medial and lateral view.
  7. Open your textbook or additional lab manual to a diagram of the human knee.
  8. Remove your cat from its bag.  Place the cat on the tray ventral side up. Drain any fluids from the bag into the “cat juice” bucket located on the demonstration table.  Place the plastic bags back into the cat container along with the rubber band.
  9. Your objective is to remove as much muscle tissue as necessary to view the bones of the distal femur, and proximal tibia and fibula along with the corresponding ligaments that support this synovial bone joint.   It is important that you do not cut any tissue that appears white and shiny on the medial and lateral sides of the knee joint because these will be the ligaments.
  10. Palpate the leg of your cat in the area of the knee.  Flex and extend the joint several times to loosen the rigor mortis.
  11. Locate the patella.
  12. Using the scalpel, cut into the muscles of the thigh 1 inch above the location of the patella.  Cut deep until you hit the bone.  Continue to cut all the way around the thigh toward the posterior and continuing back around to the anterior side. 
  13. Use the forceps or your fingers to gently pull the cut ends of the muscles of the thigh in a distal direction toward the knee. 
  14. Use your scissors to carefully cut the muscles where they are attached to the bone at the area of the anterior and posterior knee to remove them.
  15. Continue to remove any pieces of muscle until you can view the femur bone.
  16. ½ inch below the knee, palpate the tibia to locate the anterior tibial tuberosity. 
  17. ½ inch below this, once again use the scalpel to cut into the lower leg muscles down to the tibia bone.  USING VERY LITTLE DOWNWARD PRESSURE  (too much pressure and you’ll actually cut through the tibia and fibula), continue all the way around the lower leg to bisect the muscles. 
  18. Use the forceps as you did before, to pull the cut ends of the muscles in a proximal direction and cut them away using the scissors.  ALWAYS BEING CAREFUL NOT TO CUT ANY LIGAMENTS.
  19. Locate the patella again.  Now you should be able to gently pull it in a distal direction to reveal the interior of the anterior aspect of the knee. 
  20. Locate the menisci, and the anterior cruciate ligaments 

Medial meniscus:
a. semicircular
b. is larger posteriorly than anteriorly
c. its ant horn attaches to intercondylar area ant to ACL attachment
d. its post horn attaches to intercondylar area ant to PCL attachment
e. it is attached to the joint capsule at the peripheral area
f. it is attached to MCL

Lateral Meniscus
a. forms almost an entire circle similar to letter “O”.
b. the ends of its two horns are closer to each other
c. ant horn attaches to intercondylar are ant to eminences(tubercles)
d. post horn attaches to intercondylar are post to eminences(tubercles)
e. it is attached to the joint capsule at the peripheral area
f. it is NOT attached to LCL
g. it is attached to lateral edge of the lateral tibial plateu by coronary lig.
Menisci functions:
a. shock absorber
b. decrease the cartilage wear
c. spreading the stresses over jt surfaces
d. assist in lubrication
e. assist in nutrition
f. reduce friction during mvt
g. improve weight distribution via creating larger contact surface
I. peripheral area is vascularized
Ligaments:
1. MCL / medial collateral ligament      2. LCL /lateral collateral ligament
3.
ACL  /anterior cruciate ligament    4. PCL
/posterior cruciate ligament

1. MCL
a. proximal attachment: medial epicondyle
b. shape and size: long, flat band of fibrous CT
c. distal attachment: about ¼ inch  below the jt line to medial surface of the tibia
Function:
a. -becomes taut in the following positions
  -extension of the knee
  -external rotation of the tibia
  -abduction of the tibia
b. -some of the ant. fibers are tight upon knee flexion
c. -prevents ant translation of tibia against femur (similar to ACL action). This  function is an important function.

2. LCL
a. proximal attachment: lateral epicondyle
b. shape and size: short, round bundle of fibrous CT
c. distal attachment:fibular head
d. no attachment to lateral meniscus
e. popliteus muscle occurs between the LCL lig and lateral meniscus
f. lig is covered by biceps femoris tendon
g. direction of the tendon:runs slightly posteriorly from superior to inferior
.
Function:
a. -becomes taut in the following positions
  -extension of the knee
  -external rotation of the tibia
  -adduction of the tibia against femur

3. ACL
a. position and direction: from ant intercondylar area upward, backward, and laterally
b. distal attachment:anterior intercondylar area
c. proximal: medial aspect of the lateral femoral condyle