Lower Limb Alignment

Normal Anatomy

 

Mechanical Axis

 

Coronal mechanical axis Femoral mechanical axis Tibial mechanical axis Sagittal mechanical axis
Center femoral head to center of ankle Center of femoral head to center knee Center plateau to center of talus / ankle Center of femoral head to center of ankle

10mm medial to the frontal plane center

Medial tibial spine

    

Just anterior to center of knee joint

Aids in passive locking of knee joint in full extension

 

Mechanical Axis Lower LimbFemoral Mechanical AxisMechanical Axis Tibia

 

VarusValgus

Varus malalignment left knee                Valgus mechanical axis right knee

 

 

Mechanical Axis Deviation

- distance from center of knee to MA in mm

 

Anatomical Axis

 

Coronal anatomical femoro-tibial axis Femoral anatomical axis Tibial anatomical axis

Center of femoral shaft to center of knee to center of tibia

 Piriformis fossa to center knee joint Center plateau to center of talus / ankle

 5-7o valgus

- increased in shorter femurs

- decreased in longer femurs

 6o from mechanical axis  

 

Anatomic Axis FemurTibial anatomic axisTibio-femoral Anatomic Axis

 

Knee

Knee joint

aLDFA

(anatomical Lateral Distal Femoral Angle)

mLDFA

(mechanical Lateral Distal Femoral Angle)

MPTA

(medial proximal tibial angle)

 Posterior slope
3o valgus relative to MA 81o 87o 87o or 3o varus 9°
6o valgus distal femur        
3o varus proximal tibia        

 

Anatomic Lateral Distal Femoral AngleMechanical Lateral Distal Femoral AngleMedial Proximal Tibial AngleProximal Tibial Slope