The applicability of ultrasound imaging in the assessment of dynamic patella tracking: A preliminary investigation Lee Herrington a,b, ⁎ , Stephen Pearson a,b a Directorate of Sport, University of Salford, Manchester, UK b Centre for Rehabilitation and Human Performance Research, University of Salford, Manchester, UK Received 22 October 2007; received in revised form 10 December 2007; accepted 13 December 2007 Abstract The purpose of the study was to examine the effect of muscle stimulation of the Vastus Medialis Oblique (VMO) and Vastus Laterialis (VL) muscles on patella position in-vivo assessed by ultrasound scanning. Also to assess the reliability of the technique used. The position of the patella was measured using B-Mode, real time ultrasonography prior to and following the electrical stimulation of the VMO and VL muscles in 10 asymptomatic subjects. Maximal (tetanic) contraction of VMO brought about a mean medially displacement of the patella of 6.8 ± 2.9 mm and VL a mean lateral displacement of 5.6 ± 2.7 mm. The between repetition variation of displacement generated on muscle stimulation was assessed, results demonstrating a strong correlation between repetitions r = 0.85 and 0.87 (p b 0.01), for medial and lateral displacement respectively. The stimulation of either muscle (VMO or VL) brought about a consistent movement of the patella either medially for VMO or laterally for VL again demonstrating the reliability of the technique. The study found the reliability of the ultrasound technique to be good, reflecting those of previous studies which have used ultrasound to assess patella position. © 2008 Elsevier B.V. All rights reserved. Keywords: Ultrasound; Patella; Position; Muscle stimulation; Quadriceps 1. Introduction The clinical assessment of patella position and tracking is a difficult and imprecise task, not least impart due to the difficulty directly imaging the relationship between the patella and the trochlear groove [1]. Various forms of imaging including radio- graphs, computerised tomography, magnetic resonance and video fluoroscopy have been utilised to accomplish this. The alternate techniques used for assessment of position are potential either expensive, time consuming and or invasive. There are limited reports of the use of ultrasound scanning to assess patella position [2]. The use of ultrasound scans to assess patella position has obvious potential advantages as it is non-invasive, avoids radia- tion, is much cheaper and quicker to use than MRI and is easily repeatable. A number of studies have shown ultrasound (US) to be both a reliable and valid means of assessing patella position [2–5]. The studies of Herrington et al. [2], Shih et al. [4] and Shih et al. [5] showing good intra-tester reliability of the measurement and a strong correlation between the US measurement of patella frontal plane position and that made from MRI scans [2]. In a separate study Joshi and Heatley [3] showed ultrasound to have strong sensitivity; they found statistically significantly different sulcus angles between patellofemoral pain patients and matched controls. Abnormal tracking and positioning of the patella within the trochlear groove has been regarded as a significant factor in the pathogenesis of patellofemoral pain [6]. One of the major factors believed to contribute to patella position is the dy- namic stability offered to the patella by the medial and lateral vasti muscles of the quadriceps; namely, Vastus Medialis Oblique (VMO) and Vastus Lateralis (VL) [7]. It is believed Available online at www.sciencedirect.com The Knee 15 (2008) 125 – 127 ⁎ Corresponding author. Directorate of Sport, Brian Blatchford Building, University of Salford, Manchester M6 6PU, UK. Tel.: +44 1612952326; fax: +44 1612952395. E-mail address: L.C.Herrington@Salford.ac.uk (L. Herrington). 0968-0160/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.knee.2007.12.005