Blackburne-Peel ratio

A.Prof Frank Gaillard et al.

The Blackburne-Peel ratio is an alternative to Insall-Salvati ratio and is used to assess patellar height, and determine the presence of patella baja or patella alta.

A lateral radiograph of the knee with 30 degrees of flexion is obtained, and a horizontal line at the level of the tibial plateaux is drawn. Perpendicular to this line vertically and a measurement (B) made of the distance between the horizontal line and the inferior aspect of the patellar articular surface. A second measurement (A) is made along the patellar articular surface.

B/A is a measure of patellar height

  • normal value = ratio of 0.8
  • patella alta = ratio >1.0
Knee pathology

The knee is a complex synovial joint that can be affected by a range of pathologies:

Share article

Article information

rID: 7500
Tag: knee, refs
Synonyms or Alternate Spellings:

Support Radiopaedia and see fewer ads

Cases and figures

  • Figure 1: Blackburne-Peel ratio
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.