1. DR. SIDHARTH YADAV
JR1 ORTHOPAEDICS
NKPSIMS

2. AXIS
Each long bone has 2 axis :-
Mechanical axis
Anatomical axis.

3. MECHANICAL AXISStraight line connecting the joint center
points of the proximal & distal joints.
Its always a straight line whether in
frontal or sagittal plane.

4. ANATOMICAL AXISIs mid diaphyseal line.
Anatomical axis line can be
straight (frontal) & curved
(sagittal).

5. JOINT CENTER POINT
• Mechanical axis passes through
the joint center point.
• HIP
Mid point of femoral head is
identified by mose circle.
Longitudinal diameter of head.
Goniometer .

6. KNEE

7. ANKLE

8. JOINT ORIENTATION LINE
• Line representing the orientation of
a joint in a particular plane
/projection.
• ANKLE
Frontal : along the flat subchondral
line of tibial plafond.
Sagittal : line from distal tip of
posterior lip to tip of anterior lip.

9. KNEE
FRONTAL : along the subchondral
line of tibial plateau.
Line tangential to most distal point on
the femoral condyle.

10. SAGITTAL : along flat subchondral line of plateau.
Line connecting 2 points where the condyles meet the
metaphysis.

11. HIP
FRONTAL : from tip of greater trochanter to center of
femoral head.

12. JOINT ORIENTATION ANGLES
Angle formed between joint line & axis.
Each axis & joint line form 2 angles.

13. Angle between joint orientation line on opposite side of
same joint is joint line convergence angle.
Distance between anatomical axis & joint center point is
anatomical axis to joint center distance.

14. Distance between the anatomic
axis & the edge (a JED ).
a JER = a JED / Total width of
the joint.
a JCR = a JCD / Total width of
the joint.

15. HIP JOINT ORIENTATION
Initially neck shaft angle was used.
NSA normal value 125⁰-131⁰.
Line from tip of greatre trochanter to femoral head center.

16. KNEE JOINT ORIENTATION
 Tibia has slight varus relative to
mechanical axis.
Distal femur is in slight valgus.

17. Knee joint orientation measures approx. 3⁰ to
prependicular.
Blumensaat,s line angle measures 32±2.6⁰.

18. At ease At attention
STANDING POSITION

19. ANKLE JOINT ORIENTATION
Moreland et al reported a slight valgus.
Variable up to 8⁰.

20. MALALIGNMENT & MALORIENTATION
Malalingment refers to the loss of collinearity of hip ,
knee & ankle.
• MAD arises from 4 anatomic sources :-
Femoral frontal plane deformity.
Tibial frontal plane deformity.
Knee joint laxity.
Femoral or tibial condylar deficiency.

21. Angle between femoral & tibial joint line is with in 3⁰ (JLCA).
JLCA > 3⁰ is abnormal & indicates :-
Ligamentous laxity
Loss of cartilage height.

22. MALALINGMENT TEST
STEP 0 : Measure MAD
Average MAD is 8±7 mm medial.

23. STEP 1 :- Measure m LDFA.
 Normal range is 85⁰-90⁰.

24. STEP 2:- Measure MPTA.
 Normal range is 85⁰-90⁰.

25. STEP 3:- Measure JLCA
Normally joint lines are parallel within 2⁰.
Angles greater then 2⁰ are considered as a source of
MAD.

26. RULE OUT JOINT SUBLUXATION
Compare the mid point of femoral & knee joint
orientation line.
Normally they should be with in 3mm.
RULE OUT CONDYLAR MALALINGMENT

27. MALROTATION OF ANKLE & HIP
Usually leads to minimal or no MAD.
Deformity apex is at or near the ends of mechanical
axis of lower limb ( center points of ankle & hip )

28. CORA
Point at which distal & proximal axis line intersect is known
as CORA ( Center of rotation of angulation).
Axis of proximal bone segment are proximal mechanical
axis ( PMA) or proximal anatomical axis ( PAA).
Axis of distal fragment are distal mechanical axis (DMA) or
distal anatomical axis (DAA).

29. MECHANICAL AXIS PLANNING
Center point of joint is always on PMA or DMA.
2 Possible reference line that can be used are :-
Joint orientation line
Mid diaphyseal line
At knee there is very little variability in joint orientation
angles so preferred reference line is joint orientation
line.
At hip & ankle the variability is more so mid diaphyseal
line is preferred.

30. ANATOMICAL AXIS PLANNING
Mid diaphyseal line defines anatomic axis.
In diaphyseal angular deformity proximal & distal
mid diaphyseal line can be used to describe CORA.

31. CORA METHOD
STEP 0 :- MAT
Draw mechanical axis of both lower limb.
Calculate MAD.
If one side is considered as normal then its angle can be
used as template for deformed side.
If the other side also has deformity then the normal angles
are considered.

32. STEP 1 :-
Draw proximal mechanical axis line.

33. STEP 2 :-
Draw distal mechanical axis and perform MOT.

34. STEP 3 : Decide whether its uniapical or multiapical
angulation :-
Mark CORA
Measure the magnitude.
Intersection point of PMA& DMA is CORA.

35. If CORA is not at the obvious apex :-
 More then one apex of angulation.
Translation deformity.

36. Thank you…