Knee Anatomy

Question 1

O’Donoghue’s Triad

Answer 1

AKA terrible triad

ACL, MCL, medial meniscus tear

MCL attaches to both medial tibial condyle and medial lemniscus (LCL only attaches to lateral tibial condyle)

Question 2

Knee flexion (musc, inn)

Answer 2

semimemranosus, semitendinosus: L4-S1, sciatic n. tibial division; primarily L5 when being tested for strength

biceps femoris: L5-S1, sciatic n. tibial or fibular division depending on long head or short head; mostly S1 when being tested/needled

MTB distally (medial to lateral), even though membranous originates laterally and tendinosus/BF originate in joint tendon medially

sartorius

gastroc: S1-2, tibial n.

Question 3

knee extension (musc, inn)

Answer 3

quadriceps femoris:
recuts femoris, vastus intermedius, vastus medialis (VMO), vastus lateralis
L2-4 femoral n.

Question 4

knee internal rotation (musc, inn)

Answer 4

semimembranosus, semitendinosus: L4, L5, S1, sciatic n. tibial division

sartorius

gracilis: L2-4, obturator n.

Say Grace before Tea at the pes anserine
(anteromedial tibial attachment for sartorius (top), gracilis, semitendinosus (bottom))

Question 5

knee external rotation (musc, inn)

Answer 5

biceps femoris: L5-S1, sciatic n. (tibial or fibular division depending on long head or short head)

Question 6

unlocking the knee (musc, inn)

Answer 6

popliteus muscle

Question 7

knee OA - XR findings

Answer 7

typically medial compartment narrowing 1st

reactive bony sclerosis and osteophytes

subchondral cysts

Question 8

medial v lateral menisci shapes

Answer 8

MC hammer - medial meniscus is C shaped

lateral meniscus is O shaped

Question 9

Tx Meniscal tears

Answer 9

inner ⅔ is poorly vascularized; often resected

repair for outer ⅓