The Effect of Patellar Height by Using Insall Salvati Index on Pain, Function, Muscle Strength and Postural Stability in Patients with Primary Knee Osteoarthritis

Abstract

Purpose: The Insall-Salvati Index (ISI) is the ratio of the patellar tendon length to the length of the patella. This ratio is the most commonly used method for evaluating patellar placement and patellofemoral imbalance. The position of the patella is important for the knee joint function and also for biomechanics. The abnormal position of the patella may lead to patellofemoral malalignment and instability. Herein, we aimed to analyze the relationship between the ISI and pain, physical function, muscle strength, fall risk, and postural stability in patients with primary knee osteoarthritis (OA).

Methods: Sixty-two symptomatic knees of 45 patients (aged between 40 -75 years) who were suffering from the primary knee OA according to the American College of Rheumatology criteria were included retrospectively in the study. Patients with stages II and III osteoarthritis according to the Kellgren-Lawrence (K/L) radiological grading system were included. The ISI was measured on the lateral knee radiograph in a 30 degrees flexed posture. Visual Analogue scale (VAS), Western Ontario and McMaster Universities Osteoarthritis (WOMAC) and Lequesne indexes were recorded for evaluating pain and function. Tetrax Interactive Balance System was used to assess fall risk and postural stability. Isokinetic muscle strength measurements of quadriceps and hamstrings were recorded at the constant angular velocities of 60 and 180 degrees/sec.

Results: The mean age of the study population was 58.52 +/- 8.01 years. The frequency of the patellar situation types was as follows; patella alta; 15 (24.2%), patella baja; n=2(3.2%), and normal patellar height; n=45(72.6%). The mean ISI was 1.19 +/- 0.17 on the right side and 1.18 +/- 0.16 on the left side. There was no significant correlation between the ISI and VAS, WOMAC and Lequesne indexes, postural stability scores, and isokinetic measurements (r<0.3, p>0.05).

Conclusion: In primary knee OA, the ISI may not have an effect on pain, physical function, fall risk, postural stability, and isokinetic muscle strength.