Knee joint xray views

By Dr Jaskaran Singh Sandhu
MS Ortho

1. Xrays of Knee joint

2. Mechanical Axis The mechanical axis of the entire limb is evaluated using weight bearing AP 51 inch alignment radiograph with the feet pointed forward ( neutral rotation ) Mechanical axis deviation (MAD) is measured as the distance from the knee joint center to the line connecting the joint centers of the hip and ankle. The hip joint center is located at the center of the femoral head. The knee joint center is half the distance between the tibial spines to the apex of the intercondylar notch on the femur. The ankle joint center is the center of the tibial plafond.

3. Normally, the mechanical axis of the lower extremity lies 1 to 15 mm medial to the knee joint center . If the lower-extremity mechanical axis is outside this range, the deformity is described as MAD . MAD greater than 15 mm medial to the knee midpoint is varus malalignment ; any MAD lateral to the knee midpoint is valgus malalignment .

4. Normally , the anatomic axes of the femur and tibia form a valgus angle of 6 +/-2

5. Anatomical Medial proximal femoral angle Normal Range = 80 – 89 Degree s Mean value = 84 Degrees

6. Mechanical lateral proximal femoral angle Normal Range = 85-89 Degree s Mean value = 90 Degrees

7. Neck Shaft Angle Normal Range =124-136 Degree s Mean value =130 Degrees

8. Anatomical lateral distal femoral angle Mechanical lateral distal femoral angle Normal Range = 79-83 Degree s Mean value = 81Degrees Normal Range =85-89 Degree s Mean value = 88 Degrees

9. Medial P roximal Tibia Angle Normal Range = 85-89 Degree s Mean value = 83 Degrees

10. Lateral Distal tibial angle Anterior Distal tibial angle Normal Range = Degree s Mean value = Degrees Normal Range = Degree s Mean value = Degrees

11. Posterior Proximal T ibial Angle Normal Range = Degree s Mean value = Degrees

12. Radiographic measurement of Patella Blumensaat line : Lateral Radiograph to determine patella alta With knee flexed 30 degree , line is drawn through intercondylar notch Normally lower pole of patella at blumensaat line

13. Insall - salvati index Latera radiograph LT:LP = 1.0 Interpretation patella baja : <0.8 normal: 0.8-1.2 patella alta : >1.2 

14. Blackburne Peel ratio Lenght of articular surface of patella to lenght measured from articular surface of tibia to inferior pole of patella Interpretation patella baja: < 0.5 Normal ratio 0.54 – 1.06 patella alta: >1.0 

15. Patellar Height ( Caton - Deschamps ) Ratio between the articular process of the patella and distance between the articular facet of the patella and anterior corner of the superior tibial epiphysis Normal – 0.6 – 1.3 Patella baja ratio < 0.6 Patella alta – ratio > 1.3

16. Patellofemoral Congruence

17. THANKS

18. 80-89 85-95 124-136 79-83 85-90 79-87 85-90 88-92 77-84 78-82