The knee joint

Question 1

-Osteology of the knee

Answer 1

• The joint surrounds and is btwn the lat/med femoral condyles and the lat/med tibial condyles
• Nothing should be touching in the joint besides the articular (hyaline) cartilage
• Patella (level arm increaser) sits on top of the knee
• Fibula not involved in the joint

Question 2

Articular surfaces of the knee

Answer 2

• The lateral patellar surface is larger than the right one
• But the medial condyle articulation is larger than the left
• Within the synovial membrane, there are both a lateral and medial meniscus on the tibial condyles

Question 3

Structures w/in the knee

Answer 3

• ACL: anterior cruciate ligament prevents hyperextension and anterior movement of tibia (crosses lateral to medial)
• PCL: posterior cruciate ligament prevents hyperflexion and posterior movement of tibia (crosses medial to lateral)
• LCL: lateral collateral ligament prevents varus (lateral bend) at the knee
• Ligament of the popliteus muscle attaches just deep to the LCL (popliteus causes external rotation of femur to un-pop the tibia from a locked position)
• MCL: medial collateral ligament prevents valgus (medial bend) at the knee, attaches to the medial meniscus
• Most commonly injured

Question 4

The patella

Answer 4

• Forms w/in the quadriceps tendon after birth
• Connects from the quadriceps tendon to the tibia (patellar tendon)
• The tendon is technically a ligament since it connects bone->bone
• Patella has the tendency to move laterally (since the lateral surface is larger), but the vastus lateralis keeps it centered

Question 5

Mechanical factors of the knee

Answer 5

• Spongy bone near the metaphysis have high energy absorption, bearing surfaces are large
• Menisci are the ultimate weight-bearers in the knee
• They receive most of their nutrients from synovial fluid and thus do not heal well when damaged
• Bursae in the knee joint alleviate shearing loads and help glide flexion and extension (reduce friction)
• Fibrous joint capsule dissipates load around the knee
• Strong collateral/cruciate ligaments along w/ aponeuroses all reinforce the strength of the joint

Question 6

Tests for damaged components of knee

Answer 6

• Varus: tests for a damaged LCL (push the foot medially)
• Valgus: tests for a damaged MCL (push the foot laterally)
• Anterior drawer or Lachman’s test: tests for damaged ACL (pull tibia anterior)
• Posterior drawer: tests for damaged PCL (push tibia posteriorly)
• McMurray’s test tests for torn meniscus