Movement discrimination after intra-articular local anaesthetic of the ankle joint

Stuart J Down ^1*, Gordon Waddington ², Roger Adams ³ and Malcolm Thomson ⁴

¹ Australian Institute of Sport, Australia
² University of Canberra, Australia
³ University of Sydney, Australia
⁴ National Canberra Diagnostic Imaging, Australia

^* To whom correspondence should be addressed. E-mail: stu_down{at}yahoo.com.au.

Accepted 21 February 2007

Abstract

Background: The impact on clinical safety of dampening articular mechanoreceptor feedback at the ankle is unknown. Injection of the ankle joint for pain control may involve such dampening. Athletes receiving intra- articular local anaesthetic may therefore be at increased risk of sustaining ankle injuries, which are a common source of missed sporting participation.

Objectives: To determine the effect of intra- articular local anaesthetic on movement discrimination at the ankle joint.

Design: Prospective, randomised, double-blinded, placebo-controlled, cross-over trial.

Setting: Australian Institute of Sport (AIS) Medical Centre, Canberra, Australia.

Patients: Twenty-two healthy subjects (44 ankles) aged 18-26 were recruited for the three visits of the study

Interventions: Subjects were tested for their initial movement discrimination scores using the active movement extent discrimination apparatus (AMEDA). They then received ultrasound-guided intra-articular injections of local anaesthetic (lignocaine hydrochloride 2%) or normal saline, on two separate later occasions, prior to further AMEDA assessment.

Main Outcome Measures: Change in movement discrimination scores following intra-articular injection of local anaesthetic or saline.

Results: Movement discrimination scores were not significantly different from control ankles after injection of either local anaesthetic or saline into the ankle joint.

Conclusions: Neither the intra-articular injection of 2mls of lignocaine nor normal saline resulted in significant effects on movement discrimination at the ankle joint. These results suggest local anaesthetic injections into the ankle joint are unlikely to significantly affect proprioception and subsequently heighten injury risk.

Key Words: Active Movement Discrimination, Ankle Injection, Inversion, Proprioception

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