Insall Salvati Ratio

Other Names

Illustration of the Insall Salvati ratio

Lateral radiograph showing the measurement for the Insall–Salvati ratio. A was “Patella length”; B was “Length of patellar tendon”.

• Insall Salvati Ratio
• Insall-Salvati Ratio
• Insall Salvati Index

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Introduction

• Ratio of patellar tendon length to the length of the patella to determine patella height
• Most commonly used method to determine patella height based on its simplicity
• Can be affected by the presence of tibial tuberosity abnormalities

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Measurement

• Initially determined on a 30° flexed lateral knee x-ray
  • Subsequently, applied to sagittal MRI.
• Line A: patellar tendon length (TL)
  • length of the posterior surface of the tendon from the lower pole of the patella to its insertion on the tibia
• Line B: patellar length (PL):
  • Greatest pole-to-pole length
• Insall-Salvati ratio = A/B (or TL/PL)

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Interpretation

Radiographs

• Patella baja: <0.8
• Normal: 0.8-1.2
• Patella alta: >1.2

MRI

• Patella baja: <0.74
• normal: 0.74-1.5
• Patella alta: >1.5

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Pathology

• Quadriceps Tendon Rupture
• Patellar Tendon Rupture
• Patellar Instability

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Evidence

• Needs to be updated

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See Also

• Radiology Main
• Knee Pain Main

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