Joint position sense, motor imagery and tactile acuity in lateral elbow tendinopathy: A cross-sectional study

Highlights

• Wrist joint position sense was impaired in affected arms of participants with LET.

• Joint position sense impairments were observed for wrist extension only.

• Motor imagery and tactile acuity were not impaired in participants with LET.

Abstract

Background

Impairments of sensorimotor function are evident in individuals with lateral elbow tendinopathy (LET), although understanding of the mechanisms for this is lacking.

Objectives

To determine if motor imagery, tactile acuity and wrist joint position sense (JPS) are impaired in participants with unilateral LET compared to controls, whether deficits are localised to the affected side, and whether deficits relate to severity of pain.

Design

Cross-sectional study with control group.

Methods

14 participants with unilateral LET of 6 weeks or longer and 14 matched control participants were assessed bilaterally for motor imagery (left/right hand judgement task), tactile acuity (two-point discrimination test) and wrist JPS (reposition test for flexion and extension). Pain levels were measured using a numeric rating scale.

Results

Significant differences in JPS were observed for wrist extension only, such that participants with LET adopted less extended postures with their affected side when compared to their unaffected side (MD = 2.97°; p = 0.01) and to the matched-affected side of controls (MD = 4.89°; p < 0.01). No differences in tactile acuity or motor imagery were observed.

Conclusion

Altered wrist extension JPS, but not motor imagery or tactile acuity, was found in the affected side of patients with unilateral LET when compared to non-injured side and asymptomatic controls.

Introduction

Lateral elbow tendinopathy (LET), often referred as tennis elbow, is a common degenerative tendon pathology that affects 1–3% of general population (Hamilton, 1986; Shiri et al., 2006). The presenting complaint is pain at the lateral aspect of the elbow, which is aggravated by resisted wrist extension, gripping or lifting. In addition, impairments to sensorimotor functions of patients with persistent LET have been widely described. Compared to asymptomatic controls, individuals presenting with LET have demonstrated lower pain thresholds when stimulated by pressure and temperature (Coombes et al., 2012; Fernández-Carnero et al., 2009; Ruiz-Ruiz et al., 2011). Reaction time and speed of movement are also affected, where patients may perform a variety of manual tasks slower than controls (Bisset et al., 2009; Pienimäki et al., 1997). During submaximal gripping tasks, patients have been observed to adopt less extended positions with their wrist (Bisset et al., 2006). It is noteworthy that most of these sensorimotor alterations were found in both elbows of individuals with unilateral symptoms, which suggests that the underling mechanisms may involve maladaptation of the central nervous system. Findings of altered functioning of intracortical networks and maladaptive motor cortical maps related to the affected tendons in participants with LET (Burns et al., 2016; Schabrun et al., 2015) provide further support to the involvement of central nervous system processes in the aetiology of this condition.

Sensorimotor function requires integration of sensory, motor and central processes (Lephart and Fu, 2000). In the periphery, specific mechanoreceptors present in ligament, capsule and muscles detect changes in pressure, motion and velocity, producing afferent signals which are transmitted to spinal dorsal horn. These impulses may generate monosynaptic and/or polysynaptic reflexes that elicit efferent motor reaction. Afferent signals are transmitted to higher centres, such as the cerebellum and cortical sensorimotor areas, where they are interpreted and processed by complex multiregional connections among primary sensory, primary motor and dorsal premotor cortices before firing descending motor signals to the forearm muscles (Bawa et al., 2000). It is assumed that altered functioning in any of these processes may lead to impaired precision of wrist movement and stability for specific tasks (Hagert, 2010).

Appreciation of motor and sensory functioning is conducted via testing of proprioceptive senses, such as joint position sense (JPS), tactile acuity and motor imagery. Evaluation of these can provide information about someone's perception of movement and awareness of own body. JPS refers to the ability of accurately reproducing a given joint angle and can be done actively (when patient moves the joint actively to a predetermined target position) or passively (Proske and Gandevia, 2009, 2012). While a body of evidence has demonstrated impaired JPS in several musculoskeletal conditions (Stanton et al., 2016; Tong et al., 2017; Sahin et al., 2017; Baker et al., 2002), to date, there is a single study investigating elbow JPS in people with LET (Juul-Kristensen et al., 2008). Although wrist position is known to affect maximal grip strength in healthy individuals and individuals with LET display altered wrist posture during spontaneous gripping (Bisset et al., 2006; Mogk and Keir, 2003), it is currently not known whether people with LET can accurately reproduce a given wrist joint angle. The ability to distinguish two distinct points applied to the skin by touch is known as tactile acuity and can be assessed by attempting to distinguish two separate stimuli applied in varying distances. Robust evidence has shown that this ability is diminished in conditions affecting the limbs, such as complex regional pain syndrome, arm and shoulder pain (Catley et al., 2014; Breckenridge et al., 2020; Mena-del Horno et al., 2020; Heerkens et al., 2018). Motor imagery is the conscious appreciation of the self that involves both awareness of own physical body and mental simulation of movement (Moseley, 2012). Evaluation of motor imagery is usually performed using left/right judgement tasks in which individuals are tested for the time and accuracy taken when judging whether body images refer to either left or right side (Parsons, 2001). Recent studies have shown that patients with peripheral pain perform worse when recognising images of their affected side compared to their unaffected side and to controls (Breckenridge et al., 2020; Mena-del Horno et al., 2020; Breckenridge et al., 2019), however whether patients with LET are affected remains unknown.

Although investigation of pain in LET is plentiful, there is a lack of studies that evaluate other sensorimotor functions, such as JPS, tactile acuity and motor imagery. A better comprehension of these senses and the involved mechanisms may promote a broader understanding of how symptoms relate to movement processing and motion itself. Therefore, this study aimed at determining whether wrist JPS, tactile acuity and motor imagery were affected in patients with chronic LET. Secondly, we aimed at investigating whether these variables would be related to clinical outcomes.