L9.1 Knee Complex

Question 1

Knee complex

Answer 1

• Patellofemoral & tibiofibular joint (compound)
• Capsule, syno membrane, bursae, lig, menisci

Question 2

Knee Joint

Answer 2

• Tibiofemoral → a modified hinge joint (complex)
• Patellofemoral
• F/E & some rotation
• Most stable in E

Question 3

Tibiofemerol joint

Answer 3

• Directly weight bearing
• Poor bony congruence - corrected by menisci (works similar to a labrum)
• Articular capsule → extensive, attached at articular margins & menisci
  
  • Deficiencies:
    
    • ANT: Suprapatellar bursa
    • POS: Popliteal tendon

Question 4

What is the knee joint reinforced by?

Answer 4

• ANT: Patellar lig & retinaculae
• POS: Oblique & Arcuate popliteal lig
• MED: Medial collateral lig
• LAT: ITB
• INF: Coronary lig
• Also supported by muscles

Question 5

Synovial membrane

Answer 5

• Largest synovial membrane encapsulating in the body, lines interior joint capsules
• Reflects onto ACL/PCL & popliteal tendon
• Goes ANT and becomes suprapatellar bursae

Question 6

Bursae

Answer 6

• (Subcutaneous patellar bursa (may be inflamed from scrubbing floors), deep infrapatellar bursa, Subcutaneous infrapatellar bursa)
• Minimises friction
• May communicate with suprapatellar/popliteus/semimembranosus bursae
  
  • *May have spread of bursitis

Question 7

Collateral ligaments

Answer 7

• Collateral (Taut in E)
  
  • MED (tibial): Condyle of femur → condyle of tibia on ANT shaft (SUP); medial menisucus (DEEP)
    
    • Wide, from POS → ANT
    • Resists AB & ER
  • LAT (fibular):
    
    • Shorter
    • Separated from LAT meniscus by popliteal tendon
    • Resists ADD
    • Not as commonly injured

Question 8

Cruciate ligaments

Answer 8

Intracapsular but extrasynovial; Allows rotation & stabilisation in A-P direction

• ANT:
  
  • Intercondylar eminence → inner LAT condyle of femur
  • Tightens & Untwists in E
  • Assists in IR & contributes to locking of knee
  • Prevents backwards displacement of femur in WB position & fwd displacement of tibia in NWB position
  • Most prone to injury in hyperextension/flexed & rotated knee
• POS:
  
  • POS tibia → MED condyle of femur
  • Taut in full flexion
  • Opposite action of ACL
  • Prone to injury in flexed knee (bumper bar impact)

Question 9

Other ligaments

Answer 9

• Oblique popliteal lig
• Arcuate popliteal (thickening of capsule)
• Transverse genicular lig (contact menisci anteriorly)

Question 10

Menisci

Answer 10

• Separates knee joint into 2 compartments → allows separate movements
  
  • Moves with femur in rotation/tibia in F/E
• ↑congruency & stabilises knee
• ↑contact area by ~1/3
• Spread syno fluids, bears weight, protect articular surfaces
• LAT → separated by popliteal tendon
• MED → commonly injured (longer, horns further apart, less mobile due to MCL attachments)
• Removal leads to incidence of osteoarthritis (results from bone rubbing on bone)
• Moves with femur in rotation, with tibia in F/E

Question 11

Knee locking

Answer 11

• MED condyles longer than LAT (which is more ANT projected)
  
  • LAT is shorter and fits quicker, MED more oblique, rotate → lock knee
    
    • WB: FEMUR IR into fixed tibia
    • NWB: TIBIA ER into fixed femur
  • Popliteus → unlocking muscle
    
    • Draws LAT femoral condyle POS

Question 12

ANT draw test?

Answer 12

• ANT draw test: Femur kept stable → move leg ANT easily → ACL torn
  
  • *same test but opposite for PCL

Question 13

Blood & Nerve supply?

Answer 13

• Blood supply: Anastomoses b/w branches of femoral, popliteal & genicular A
• Nerve supply: Branches of obturator, femoral & sciatic

Question 14

What is conjunct/adjunct rotation?

Answer 14

• Conjunct rotation:
  
  • locking (passive): femur rotates internally relative to fixed tibia
  • Unlocking (active): popliteus pulling on LAT epicondyle → LAT rotation
• Adjunct rotation:
  
  • Discrete actions occurring
  • IR/ER with flexed knee

Question 15

Genu varum/valgum?

Answer 15

• Genu Varum → Bowl legged position
• Genu valgum → knocked knee position

Question 16

Patellofemoral joint

Answer 16

• b/w POS surface of patellar & ANT surface of femoral condyles
• ↑Moment arm of quadriceps; non weight bearing
• Permits vertical gliding of patellar by bursa → inflammation leads to knee stiffness
  
  • Articularis genu muscle pull syno membrane away → prevents syno membrane impingement during patellar gliding
• Quad tendon → provides leverage during E but is a hinderance at the start of E from flexion

Question 17

Patellar dislocation?

What is it stopped by?

Consequence of maltracking?

Answer 17

• Patellar dislocation: LAT
  
  • Caused by angle b/w patellar tendon & patellar ligmament (Females > males)
  • Quads (rectus femoris) + ITB pulling patellar tendon laterally
• Patellar dislocation stopped by:
  
  • V.M.O
  • Medial patellar retinaculum (passive support)
  • Raised lip on lat femoral condyle
• Chondramalacia patellar: Maltracking - degeneration of cartilage of patellar

Question 18

Tibiofibular joint

Answer 18

• (Not part of the knee joint) Good stability & rare dislocation
• Prox: Plane synovial
  
  • Some gliding
  • Reinfornced by ANT & POS tibiofibular lig
• Distal: Fibrous syndesmoses
  
  • ↓movement → becomes shock absorber
  • Prevents tib-fib separation
  • ANT,POS, interosseous tibiofibular lig