improvements in quadriceps sensorimotor function and disability of ...

British Journal of Rheumatology 1998;37:1181–1187

IMPROVEMENTS IN QUADRICEPS SENSORIMOTOR FUNCTION AND DISABILITY OF PATIENTS WITH KNEE OSTEOARTHRITIS FOLLOWING A CLINICALLY PRACTICABLE EXERCISE REGIME M. V. HURLEY and D. L. SCOTT* Physiotherapy Division, School of Biomedical Sciences and *Department of Rheumatology, School of Medicine and Dentistry, King’s College, London SUMMARY Objective. Quadriceps sensorimotor dysfunction may be important in the pathogenesis of knee osteoarthritis (OA) and a determinant of disability. Exercise regimes can increase quadriceps strength, but whether this improves proprioception and reduces disability is uncertain. Moreover, research regimes involve protracted treatment which is clinically impracticable. Methods. We compared quadriceps sensorimotor function and disability in 60 patients with knee OA, before and after an exercise regime, with a control group (n = 37) who did not exercise. Results. Exercise improved quadriceps strength (mean change, 95% CI; 73 N, 26–119 N ), voluntary activation (14%, 5–20%), knee joint position sense (0.6°, 0.1–1.8°), and reduced the Lequesne Index (3.5, 0.5–4) and aggregate time of four activities of daily living (8.4 s, 0.2–16.7 s). At 6 month follow-up, these improvements were maintained. The parameters of the control group were unchanged. Conclusions. These results substantiate the association between quadriceps sensorimotor dysfunction and disability, emphasizing the importance of quadriceps exercise in the management of knee OA. The regimen is relatively brief and clinically practicable, but could be adapted to make it more cost effective. K : Knee osteoarthritis, Quadriceps strength, Proprioception, Disability, Exercise therapy.

K osteoarthritis (OA) is a prevalent, painful and disabling arthritic condition [1]. Its management has considerable direct and hidden health care costs, and consequently it imposes a major socio-economic burden [2, 3]. However, effective and cost-effective management regimes for patients with knee OA remain unclear. Most patients are maintained on simple analgesia or non-steroidal anti-inflammatory drugs to provide symptomatic relief of pain [4, 5]. Unfortunately, these agents can have serious side-effects which contribute to the hidden costs of knee OA [6, 7]. If pain and disability become very severe, the patient may be referred for an orthopaedic assessment. However, the utilization of orthopaedic procedures for knee OA is poor and usually delayed [8] because they are perceived to be relatively expensive and unsuccessful, with inherent risks. Both drug and surgical management aim for symptomatic pain relief, with the unsubstantiated assumption that this will automatically lead to better function [9–12]. Neither form of management directly addresses quadriceps weakness, which is an early and common clinical feature of knee OA [12–15] and an important determinant of disability [1, 16 ]. Exercise can increase quadriceps strength regimes, but these efficacious research regimes necessitate frequent and numerous exercise sessions [12–14, 17–19]. The costs and logistics of these protracted exercise regimes preclude their clinical implementation. In addition to motor deficits, quadriceps sensory

dysfunction, i.e. decreased proprioceptive acuity, has recently been demonstrated in patients with knee OA and proposed as a factor in the pathogenesis or progression of the condition [15, 16, 20–22]. If correct, restoration of these sensorimotor deficits with rehabilitation may retard progression of knee OA and reduce disability. This study investigated whether a relatively brief exercise regime increased quadriceps strength and proprioceptive acuity, and reduced disability in patients with knee OA. METHODS Patients A total of 111 patients with knee OA were recruited from a rheumatology out-patient department; some were new referrals to the hospital, but most had been reviewed by the medical staff during the past year and discharged back to their general practitioner’s care. The diagnosis was made by a rheumatologist from the clinical history, radiographic changes and physical examination of the patient. All the patients fulfilled the American College of Rheumatology criteria for knee OA [23]. The predominant complaint of all the patients was knee pain; patients who reported co-existent mild symptomatic OA in other joints (i.e. contralateral knee, hands, hips, ankles or spine) were not excluded from the trial unless the pain from these other joints interfered with the performance of the assessment procedures. Patients were also excluded if they had received intra-articular steroid injections in the preceding 6 months, physiotherapy for their knee during the preceding 12 months, or had other unstable medical conditions.

Submitted 10 March 1998; revised version accepted 1 July 1998. Correspondence to: M. Hurley, Physiotherapy Division, KCL, Rehabilitation Research Unit, King’s Healthcare (Dulwich), East Dulwich Grove, Dulwich, London SE22 8PT.

© 1998 British Society for Rheumatology 1181

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Assessment procedures The assessment procedures have been described in detail elsewhere [16 ], but brief details are given below. Isometric quadriceps force was assessed during an isometric maximum voluntary contraction (MVC ) with the patients seated on a specially constructed chair to which a strain gauge system was attached. Quadriceps voluntary activation was estimated by superimposing percutaneous electrical stimulation upon isometric MVCs and comparing the relative amplitudes of the superimposed twitches to the size of the resting twitches [24]. It is vital that each patient exerts maximal voluntary effort so that maximum strength and voluntary activation can be assessed. To facilitate this, each patient was familiarized with the test procedures, received vigorous verbal encouragement and had visual feedback of their quadriceps strength from a force trace displayed on a computer monitor. Three isometric quadriceps MVCs with superimposed electrical stimulation were recorded, but only the largest MVC was used in the data analysis. Knee joint position sense (JPS) was used as an estimate of proprioceptive acuity. An electrogoniometer (Penny and Giles, Gwent) was used to measure the mean error of 10 actively reproduced knee joint angles, randomly selected between 90° flexion and full knee extension [16 ]. Objective assessment of functional performance was obtained by timing the patients walking as fast as they could for 50 feet [25]; standing up from a chair and walking 50 feet [26 ]; ascent of a straight flight of stairs, consisting of 11 steps each 12 cm high; descent of the straight flight of stairs. Because any single test of functional performance imparts little information about the patient’s overall functional ability, by aggregating the time of the four activities a better objective assessment of the patient’s overall functional capabilities can be obtained; this was called the aggregate functional performance time (AFPT ) [16 ]. The Lequesne Index for knee OA is a pathologyspecific subjective assessment of the patient’s pain and disability which is scored between 0 and 24 points, and can be used to categorize arbitrarily the severity of the patient’s disability as mild/moderate (