Objective: To determine intrarater reliability of clinical examinations and radiographic variables that proposed to identify patients with lumbar segmental instability.

Materials & Methods: In this descriptive and methodological research, 15 patients with chronic non specific low back pain aged 22-43 years with non probability and simple selection (sample of convenience) participated. Clinical examinations included pain intensity, flexion and extension range of motion (ROM) with modified schober method, aberrant movement patterns, ito method of flexion and extension endurance test, sid support test, bilateral straight leg rising (SLR) & sit-up, prone instability test and oswestry index. Radiographic variables included: 1) Quantity of movement (sagital plane transition & rotation) measured with Dupuis and Panjabi method 2) Quality of movement (instability factor, centre of rotation & Centroid). Proposed method from Putto was used for flexion-extension radiography. Five x-rays were taken in neutral, full flexion & extension, mid range of flexion & extension positions from lateral view. We used ICC for reliability of quantitative variables, and Kappa statistic for nominal variables.

Results: Reliability of Pain intensity (ICC=0.89), flexion (ICC=0.93) & extension (ICC=0.74) ROM, Sid support test (ICC=0.85-0.86), extension (ICC=0.86) & flexion (ICC=0.82) endurance were high. Kappa value for aberrant movement patterns (k=0.66), bilateral SLR & sit-up (k=0.65), prone instability test (k=0.66) were substantial. Centre of rotation on X axis (ICC=0.99) & Y axis (ICC=0.96), rotation with Dupuis (ICC=0.83) & Panjabi (ICC=0.88) had very high reliability. Centroid length with 3 (ICC=0.60) & 5 (ICC=0.64) x-rays, instability factor with 3 (ICC=0.61) & 5 (ICC=0.72) x-rays, transition with Dupuis (ICC=0.69) & Panjabi (ICC=0.76) method had moderate to high reliability.

Conclusion: Clinical examinations includig pain intensity, flexion & extension ROM, sid support test, extension & flexion endurance and oswestery index have high to very high reliability. Aberrant movement patterns, bilateral SLR & sit-up and prone instability test have substantial agreement. Radiographic variables have moderate to very high reliability.