A. Knee joint - consists of 2 articulations within a single synovial cavity: 1) femur and patella and 2) femur and tibia
- 1. menisci: two intracapsular fibrocartilages which create concave receptacles for the convex femoral condyles
- a. medial meniscus
- b. lateral meniscus
- 2. cruciate ligaments - two crossing intracapsular ligaments named for the position of their tibial attachment
- a. anterior cruciate - restricts anterior displacement of the tibia relative to the femur
- b. posterior cruciate - restricts posterior displacement of the tibia relative to the femur
- 3. extracapsular ligaments
- a. fibular (lateral) collateral ligament - separated from the joint capsule by the popliteal tendon
- b. tibial (medial ) collateral ligament - adherent to the joint capsule and underlying medial meniscus
- 4. Movements - flexion/extension is the major movement at the knee; slight amounts of medial/lateral rotation can occur when the knee is flexed
- a. medial/lateral translation is prevented by intercondylar eminence of the tibia
- b. extension is limited by all ligaments (cruciate and collateral) and posterior joint capsule; the knee cannot extend past the vertical
- c. flexion is limited by the soft tissue of calf
- d. anterior translation (sliding) is restricted by anterior cruciate ligament
- e. posterior translation (sliding) is restricted by posterior cruciate ligament
- f. abduction is prevented primarily by the medial collateral ligament and secondarily by the cruciate ligaments
- g. adduction is prevented primarily by the lateral collateral ligaments and secondarily by the cruciate ligaments
- h. medial rotation is restricted by the cruciate ligaments
- i. lateral rotation is restricted by the collateral ligaments
III. Myology
- A. flexors
- 1. sartorius (femoral n)
- 2. gracilis (obturator n)
- 3. semitendinosus (tibial n.)
- 4. semimembranosus (tibial n.)
- 5. long head of biceps femoris (tibial n.)
- 6. short head of biceps femoris (common peroneal n.)
- B. extensors
- 1. quadriceps femoris (femoral n.)
- a. rectus femoris
- b. vastus medialis
- c. vastus intermedius
- d. vastus lateralis
- C. medial rotator
- 1. popliteus (tibial n.) - primary
- D. lateral rotator
- 1. biceps femoris- both heads (tibial & common peroneal n.)
IV. adductor canal - narrow intermuscular space running between apex of femoral triangle and adductor hiatus; femoral artery and vein pass completely through it to enter the popliteal fossa whereas the saphenous nerve exits prior to the adductor hiatus
V. popliteal fossa - diamond shaped intermuscular space posterior to the knee joint
- A. boundaries
- 1. superomedial: semitendinosus and semimembranosus
- 2. superolateral: biceps femoris
- 3. inferomedial: medial head of gastrocnemius
- 4. inferolateral: lateral head of gastrocnemius
- B. contents
- 1. popliteal artery and vein
- 2. sciatic nerve - typically divides into tibial and common peroneal nerves within fossa
- 3. small saphenous vein - pierces deep fascia to join popliteal vein
VI. Arteries
- A. popliteal artery is continuation of femoral artery at adductor hiatus; in addition to muscular branches, typically gives rise to 5 genicular branches within popliteal fossa; popliteal a terminates at lower border of popliteal fossa as anterior and posterior tibial aa
- 1. superior lateral genicular - arises above head of LG
- 2. superior medial genicular - arises above head of MG
- 3. middle genicular - pierces posterior joint capsule to supply cruciate ligaments
- 4. inferior lateral genicular - lies deep to head of LG but supf to popliteus
- 5. inferior medial genicular - lies deep to head of MG
- B. Genicular anastomosis - formed by branches of popliteal, femoral and anterior tibial aa
- 1. femoral branches (direct and indirect): descending genicular a and descending br of lateral circumflex femoral a
- 2. popliteal branches: superior medial genicular, superior lateral genicular, inferior medial genicular and inferior lateral genicular aa
- 3. anterior tibial branch: anterior tibial recurrent a
VII. Motor innervation of the hindlimb
- N.B. You are responsible for knowing the innervation of every muscle of the hindlimb. The following attempts to show that there is a systematic relationship between a muscle's developmental origin, its position in the limb and its innervation. You will not be examined on this material beyond knowing (1) each muscle's innervation and (2) which ventral rami form the lumbar (L1-L3 and most of L4) and sacral (lumbosacral trunk (L4-5), S1-3, part of S4) plexi.
- A. dorsal division nerves: innervate hindlimb musculature arising from the ilium and all anterior and lateral compartments
- 1. lumbar plexus: femoral nerve innervates the anterior compartment of the hip and thigh
- 2. sacral plexus
- a. inferior gluteal - gluteus maximus
- b. superior gluteal - gluteus medius and minimus, tensor fascia lata
- c. common fibular (peroneal) - short head of biceps (lateral compartment of thigh); anterior and lateral (peroneal) compartments of leg; dorsum of foot
- B. ventral division nerves: innervate hindlimb musculature arising from the ischium and pubis and all posterior and medial compartments
- 1. lumbar plexus - obturator nerve innervates all muscles of medial compartment except frequently pectineus
- 2. sacral plexus
- a. nerve to obturator internus - obturator internus and superior gemellus
- b. nerve to quadratus femoris - quadratus femoris and inferior gemellus
- c. tibial nerve - posterior compartments of thigh and leg; planta of foot
The following figures and table may be helpful in understanding and learning the innervation of the hindlimb:
