Blackburne-Peel ratio

The Blackburne-Peel ratio is an alternative to Insall-Salvati ratio and is used to assess patellar height including patella alta and baja. 

Usage

The Blackburne-Peel ratio has higher interobserver reliability compared to the Insall-Salvati ratio and can also be used when the tibial tuberosity is abnormal (e.g. Osgood-Schlatter disease, osteotomy) as it does not rely on this landmark ^3,4.

Measurement

A lateral radiograph of the knee with 30° of flexion is obtained, and a horizontal line at the level of the tibial plateau is drawn. Perpendicular to this line (i.e. vertically) two measurements are made:

• A: along the patellar articular surface
• B: distance between the horizontal line and the inferior aspect of the patellar articular surface

B/A is a measure of patellar height

Interpretation

• patella baja: <0.5
• normal: 0.8
• patella alta: >1.0