Tibial External Rotation Test for Patellar Instability. (2nd March 2022)

• Record Type: Journal Article
• Authors: Zarins, Bertram
• Is Part Of: Journal of bone and joint surgery. Volume 104:Number 5(2022)
• Page Start: e16
• Publication Date: 2022-03-02
• Subjects: Bones -- Surgery -- Periodicals; Joints -- Surgery -- Periodicals; Orthopedics -- Periodicals; Orthopedics; General Surgery; Bone Diseases; Joint Diseases; Bones -- Surgery; Joints -- Surgery; Orthopedics; Bot (anatomie); Gewrichten; Chirurgie (geneeskunde); Periodicals; Electronic journals; Periodicals; 617.47005
• DOI: 10.2106/JBJS.21.00449
• Languages: English
• ISSNs: 0021-9355

Abstract

Abstract : Background: There is no dynamic physical examination test that reproduces patellar instability or the effect of tibial rotation on patellar tracking. Methods: This article describes a provocative physical examination test that can reproduce lateral patellar subluxation: the tibial external rotation test (TERT). The principle behind the TERT is to vary the quadriceps angle (Q-angle) by changing the rotation of the tibia with the knee at 90° of flexion and asking the patient to forcefully extend the knee against resistance. If the patella subluxates at about 25° of flexion when the tibia is held in the externally rotated position and the knee is extended against resistance (i.e., with an increased Q-angle) but is more stable when the same is done when the tibia is internally rotated, the test is positive. Results: The TERT confirmed the diagnosis of patellar instability and helped determine if medialization of the tibial tubercle should be performed. Conclusions: The TERT is a provocative physical examination test that can cause the patella to subluxate laterally. The TERT can simulate the effect of medializing the tibial tubercle on patellar tracking. Level of Evidence: Diagnostic Level V . See Instructions for Authors for a complete description of levels of evidence.