Patella height

There are three ways to measure patella height (knee needs to be slightly flexed about 30 degrees to tension extensor mechanism)

1. Blumensaat's line

    With the knee flexed 30 degrees a line drawn through the roof of the intercondylar notch should touch the tip of the patella. NOT VERY RELIABLE

2. Insall Salvati index

    Length of Patella (LP) / Length of Patella tendon (LT) LP/LT = 1 (Standard deviation 0.13)

3. Blackburn and Peel

    Useful if not sure where tibial tuberosity is, ie. old Osgood Schlaters disease.

 

    Lateral radiograph, knee flexed at least 30. Project a line forwards along the tibial plateau and make two measurements:

A - Perpendicular height of the lower end of the articular surface of the patella from the tibial plateau line.

B - Length of the articular surface of the patella

A / B = 0.8 (0.65-1.38)

Blackburn and Peel stated the normal ratio as 0.8, patellar altais greater than I.0

 


References

 

Blumensaat, C. (1938) Die Lageabweichungen und Verrenkungen der Kniescheibe. Ergebnisse der Chirurgie und Orthop#{228}die, 31, 149-223.


Insall, J., and Salvati, E. (1971) Patella position in the normal knee joint. Radiology, 101, 101-104.

 

JS Blackburne and TE Peel; A new method of measuring patellar height;  J Bone Joint Surg Br, May 1977; 59-B: 241 - 242

 


Last updated 27/10/2008
Page created by: Lee Van Rensburg
Correction by: Gideon Heinert
www.easytrauma.co.uk
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