Insall-Salvati Ratio for Assessment of Patella Height

Lateral view of the knee shows a method of measuring patella height in this patient who fell and was unable to extend the knee.

Facts: Insall-Salvati Method

• Patella height expressed as a ratio of patellar tendon length (LT) to greatest diagonal length of the patella (LP)
• Most commonly used method to assess patellar height in all degrees of flexion
• LT = length of tendon = tendon origin at inferior patella to its insertion at the tibial tubercle
• LP = length of patella = diagonal length of the patella
• Normal = LT roughly is equal to LP, any variation more than 20% considered abnormal
• LT:LP more than 1.2 = patella alta
• LT:LP less than 0.8 = patella infera

Our case: LT:LP is greater than 2, this is patella alta due to traumatic complete patellar tendon rupture.

Reference:

Scuderi GR. The Patella, 1995.