The Orthopaedic Research Institute–Tennis Elbow Testing System: a modified chair pick-up test—interrater and intrarater reliability testing and validity for monitoring lateral epicondylosis

Lateral epicondylosis is a degenerative overuse tendinopathy involving the extensor tendons of the forearm, predominantly the extensor carpi radialis brevis, in the region of the lateral epicondyle of the elbow. The Orthopaedic Research Institute–Tennis Elbow Testing System (ORI-TETS) is designed to record objective measurements of force generated with a simulated chair pick-up test. Interrater reliability of the ORI-TETS was excellent, with high intraclass correlation coefficients (ICCs) for right arm mean peak force of 0.93, left arm mean peak force of 0.84, right arm mean total force of 0.93, and left arm mean total force of 0.86. The ORI-TETS also demonstrated excellent intrarater reliability, with ICCs ranging from 0.9 to 0.97. The relative technical error of the ORI-TETS for all measurements ranged from 5.8% to 7.2%. Testing patients with lateral epicondylosis (N = 16) and comparing analog pain scores with ORI-TETS testing demonstrated a strong negative relationship between the two parameters (Spearman ρ, −0.87 to −1.0). Thus, the ORI-TETS is a reliable and reproducible testing system for the forearm extensors. The testing system is inexpensive, takes 5 minutes to perform, and demonstrates good predictive value for objectively assessing patients with lateral epicondylosis. This system could be used for routine clinical monitoring of patients with lateral epicondylosis.