Static postural sway, proprioception, and maximal voluntary quadriceps contraction in patients with knee osteoarthritis and normal control subjects

No difference between home-based strength training and home-based balance training on pain in patients with knee osteoarthritis: a randomised trial

QUESTION

Is four weeks of home-based balance training more effective than four weeks of home-based strength training at decreasing pain in patients with knee osteoarthritis?

DESIGN

Randomised trial with concealed allocation and assessor blinding.

PARTICIPANTS

48 community volunteers with knee osteoarthritis.

INTERVENTION

Two groups undertook home-based exercise programs: one group performed balance training and the other performed strength training. Participants performed 30 repetitions/leg/day, 5 days/week for four weeks.

OUTCOME MEASURES

The Knee injury and Osteoarthritis Outcome Score was used to evaluate pain, which was the primary outcome. Secondary outcomes were the other subscales of the Knee injury and Osteoarthritis Outcome Score (other symptoms, function in daily living, function in sport and recreation, knee-related quality of life), strength, and mobility.

RESULTS

There was no significant difference between groups for pain (mean difference -3 points out of 100, 95% CI -10 to 5). The only between-group difference in the Knee injury and Osteoarthritis Outcome Score was in knee-related quality of life, where the strength group improved 17 points out of 100 (95% CI 5 to 28) more than the balance group. There was no significant difference between groups for strength. The only between-group difference in mobility was in the time taken to walk downstairs, where the strength group improved by 2 s (95% CI 0 to 3) more than the balance group.

CONCLUSION

There was no difference in pain between home-based strength training and home-based balance training in patients with knee osteoarthritis.

TRIAL REGISTRATION

NCT 00687726.

Effect of tibial re-alignment surgery on single leg standing balance in patients with knee osteoarthritis

BACKGROUND

Standing balance is impaired in individuals with knee osteoarthritis and is associated with disease severity. The effects of surgical interventions on standing balance have received little attention. The purpose of the present study was to examine measures of balance during tests of single-limb standing before and after medial opening wedge high tibial osteotomy--a lower limb re-alignment procedure for those with varus alignment and knee osteoarthritis.

METHODS

Standing balance was assessed in 49 individuals prior to and 12 months following medial opening wedge high tibial osteotomy. Participants performed three trials of single-limb balance lasting 10s each while standing on a force platform. Anteroposterior and mediolateral coordinates of the centre of pressure were obtained from the force platform and used to calculate the total centre of pressure path length as well as the range and variability (standard deviation) of the anteroposterior and mediolateral coordinates.

FINDINGS

Though all centre of pressure measures were lower following high tibial osteotomy, none reached statistical significance (P>0.05) and effect sizes were small (d<0.34). The largest mean improvement was 7.6% (95% confidence interval: -0.7-15.8%).

INTERPRETATION

Results indicate that standing balance in individuals with knee osteoarthritis is not significantly different following high tibial osteotomy surgery. Standing balance in this patient population is a complex process not entirely dictated by disease symptoms or structural factors such as alignment.

Effect of baseline quadriceps activation on changes in quadriceps strength after exercise therapy in subjects with knee osteoarthritis

OBJECTIVE

To examine whether pretreatment magnitude of quadriceps activation (QA) helps predict changes in quadriceps strength after exercise therapy in subjects with knee osteoarthritis (OA). We hypothesized that subjects with lower magnitudes of QA (greater failure of muscle activation) would have smaller gains in strength compared with those with higher magnitudes of QA following exercise therapy.

METHODS

One hundred eleven subjects with knee OA (70 women) participated. Baseline measures included demographic information, quadriceps muscle strength, and QA using a burst-superimposition isometric torque test. Following baseline testing, subjects underwent a 6-week supervised exercise program designed to improve strength, range of motion, balance and agility, and physical function. On completion of the program, quadriceps strength and QA were reassessed. Multiple regression analysis was used to determine whether baseline QA predicted quadriceps strength scores at the 2-month followup.

RESULTS

Bivariate correlations demonstrated that baseline QA was significantly associated with quadriceps strength at baseline (rho = 0.30, P < 0.01) and 2-month followup (rho = 0.23, P = 0.01). Greater magnitude of baseline QA correlated with higher strength. While controlling for baseline quadriceps strength and type of exercise therapy, the level of QA did not predict quadriceps strength at the 2-month followup (beta = -0.04, P = 0.18).

CONCLUSION

Baseline QA did not predict changes in quadriceps strength following exercise therapy. Measurement of QA using the central activation ratio method does not appear to be helpful in identifying subjects with knee OA who will have difficulty improving quadriceps strength with exercise therapy.

Quadriceps strength and the risk of cartilage loss and symptom progression in knee osteoarthritis

OBJECTIVE

To determine the effect of quadriceps strength in individuals with knee osteoarthritis (OA) on loss of cartilage at the tibiofemoral and patellofemoral joints (assessed by magnetic resonance imaging [MRI]) and on knee pain and function.

METHODS

We studied 265 subjects (154 men and 111 women, mean+/-SD age 67+/-9 years) who met the American College of Rheumatology criteria for symptomatic knee OA and who were participating in a prospective, 30-month natural history study of knee OA. Quadriceps strength was measured at baseline, isokinetically, during concentric knee extension. MRI of the knee at baseline and at 15 and 30 months was used to assess cartilage loss at the tibiofemoral and patellofemoral joints, with medial and lateral compartments assessed separately. At baseline and at followup visits, knee pain was assessed using a visual analog scale, and physical function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index.

RESULTS

There was no association between quadriceps strength and cartilage loss at the tibiofemoral joint. Results were similar in malaligned knees. However, greater quadriceps strength was protective against cartilage loss at the lateral compartment of the patellofemoral joint (for highest versus lowest tertile of strength, odds ratio 0.4 [95% confidence interval 0.2, 0.9]). Those with greater quadriceps strength had less knee pain and better physical function over followup (P<0.001).

CONCLUSION

Greater quadriceps strength had no influence on cartilage loss at the tibiofemoral joint, including in malaligned knees. We report for the first time that greater quadriceps strength protected against cartilage loss at the lateral compartment of the patellofemoral joint, a finding that requires confirmation. Subjects with greater quadriceps strength also had less knee pain and better physical function over followup.

Muscle and exercise in the prevention and management of knee osteoarthritis: an internal medicine specialist's guide

This article outlines the influence of muscle activity on knee-joint loading, describes the deficits in muscle function observed in people with knee osteoarthritis, and summarizes available evidence pertaining to the role of muscle in the development and progression of knee osteoarthritis. The article focuses on whether muscle deficits can be modified in knee osteoarthritis and whether improvements in muscle function lead to improved symptoms and joint structure. This article concludes with a discussion of exercise prescription for muscle rehabilitation in knee osteoarthritis.

Posture and equilibrium in orthopedic and rheumatologic diseases

Posture and balance may be affected in many spine or lower-limb disorders. An extensive evaluation including clinical tests and movement analysis techniques may be necessary to characterize how rheumatologic or orthopedic diseases are related to static or dynamic changes in postural control. In lower limbs, unbalance may be related to a decreased stability following arthrosis or ligament injuries at knee or ankle levels, while hip lesions appear less associated with such troubles. Spinal diseases at cervical level are frequently associated with postural changes and impaired balance control, related to the major role of sensory inputs during stance and gait. At lower levels, changes are noticed in major scoliosis and may be related to pain intensity in patients with chronic low-back pain. Whatever the initial lesion and the affected level, improvement in clinical or instrumental tests following rehabilitation or brace wearing provides argument for a close relationship between rheumatologic or orthopedic diseases and related impairments in posture and balance control.

Total knee arthroplasty: muscle impairments, functional limitations, and recommended rehabilitation approaches

The number of total knee arthroplasty (TKA) surgeries performed each year is predicted to steadily increase. Following TKA surgery, self-reported pain and function improve, though individuals are often plagued with quadriceps muscle impairments and functional limitations. Postoperative rehabilitation approaches either are not incorporated or incompletely address the muscular and functional deficits that persist following surgery. While the reason for quadriceps weakness is not well understood in this patient population, it has been suggested that a combination of muscle atrophy and neuromuscular activation deficits contribute to residual strength impairments. Failure to adequately address the chronic muscle impairments has the potential to limit the long-term functional gains that may be possible following TKA. Postoperative rehabilitation addressing quadriceps strength should mitigate these impairments and ultimately result in improved functional outcomes. The purpose of this paper is to describe these quadriceps muscle impairments and discuss how these impairments can contribute to the related functional limitations following TKA. We will also describe the current concepts in TKA rehabilitation and provide recommendations and clinical guidelines based on the current available evidence.

LEVEL OF EVIDENCE

Therapy, level 5.

A new measurement method for spine reposition sense

Background

A cost effective tool for the measurement of trunk reposition sense is needed clinically. This study evaluates the reliability and validity of a new clinical spine reposition sense device.

Methods

The first part of this three part investigation included 45 asymptomatic subjects examined in the first 20 repeated trials portion assessing spine reposition sense. The second portion, test-retest, examined 57 asymptomatic subjects. Initial testing consisted of subjects sitting on the device and performing 20 trials of a self-determined 2/3 trunk flexion position. The second portion of the study involved 7 trials of trunk flexion performed twice. The angular position for each trial was calculated and the mean reposition error from the initial 2/3 position was determined. For the third portion, the new device was compared to the Skill Technologies 6D (ST6D) Imperial Motion Capture and Analysis System.

Results

ICC (3,1) for trials 4–7 was 0.79 and 0.76 for time one and time two, respectively and the test-retest ICC (3,k) was 0.38. Due to the poor test-retest ICC, the Bland Altman method was used to compare test and retest absolute errors. Most measurement differences were small and fell within the 95% confidence interval. Comparable measures between the two methods were found using the Bland Altman method to compare the reposition sense device to the ST6D system.

Conclusion

The device may be a cost effective clinical technique for sagittal trunk reposition sense measurement.

The effect of total knee replacement surgery on gait stability

The purpose of this study was to investigate the effect of knee pain and total knee replacement (TKR) surgery on the gait stability of knee osteoarthritis (OA) patients compared to controls. Gait spatio-temporal measures, center of mass kinematics and pain levels of 21 TKR subjects and 21 controls (CON) were assessed during level walking and obstacle crossing at two testing periods, pre-surgery (P1) and 6 months post-surgery (P2). The TKR patients reported greater pain and disability than CONs at P1 and P2, walked and negotiated the obstacle more slowly and had a shorter stride length than CONs. After surgery, the TKR center of mass-center of pressure (COM-COP) separation distance and the peak anterior inclination angle were significantly smaller than CONs. Pain was found to be significantly related to sagittal plane measures, but not to similar measures in the frontal plane. The data suggest that total knee replacement surgery and pain affect gait stability predominantly in sagittal plane variables. The TKR subjects used a conservative strategy to manage the COM and COP in the sagittal plane, possibly to reduce the kinetic demands on the involved limb.

Effects of anterior cruciate ligament (ACL) injury on muscle activity of head, neck and trunk muscles: a cross-sectional evaluation

This study evaluated the that effects a pathology of the knee, due to an anterior cruciate ligament (ACL) injury, has on muscular activity of neck, head, and trunk muscles. Twenty-five (25) subjects (mean age 28+/-9 years) with ACL injury of the left knee were compared with a control no-pathology group. Surface electromyography (sEMG) at mandibular rest position and maximal voluntary clenching (MVC) wasused to evaluate muscular activity of the areas: masseter, anterior temporalis, posterior cervicals, sternocleidomastoid (SCM), and upper and lower trapezius. The sEMG activity of each muscle, as well as the asymmetry index between the right and the left sides, were compared between the two groups. Subjects in the study group showed a significant increase in the asymmetry index of the sEMG activity of the anterior temporalis at mandibular rest position (p<0.05). At rest, the areas of anterior temporalis and masseter in the control group showed a significantly lower sEMG activity compared with subjects in the study group, both in the right and the left sides (p<0.05). The same was found for the sEMG activity of the areas of SCM and lower trapezius. At MVC, the right areas of anterior temporalis and masseter in the study subjects showed a significantly lower sEMG activity compared with the control group. The same was observed for the lower trapezius area, both in the right and the left sides. In general, ACL injury appears to provide a change in the sEMG activity of head, neck and trunk muscles.

The effect of a single haemodialysis session on functional mobility in older adults: a pilot study

OBJECTIVES

To undertake balance and functional mobility assessments in older maintenance haemodialysis patients before and after haemodialysis as a pilot study in order to gain initial data and to assess the feasibility and acceptability of this type of study.

DESIGN

Postural sway, three-metre timed "up and go" test (TGUGT), and dynamic single leg extensor power (LEP) were measured before and after a haemodialysis session.

SETTING AND SUBJECTS

Male and female maintenance haemodialysis patients aged over 60 years attending the Nottingham City Hospital.

MAIN MEASURES

Objective outcome measures were postural sway number and sway path (mm) by balance performance monitor, timed three-metre "up and go" test (s), and leg extensor power (W). Blood pressure and weight reductions were also measured. Subjective assessments of practicality and acceptability were made.

RESULTS

Twenty-two patients enrolled. Complete data sets were collected for 14 subjects (11 male, three female). Results were analysed using the Wilcoxon signed ranks test for nonparametric data. There was no significant difference before and after dialysis in postural sway, timed "up and go" or leg extensor power. Eight patients did not complete the study and the reasons are examined.

CONCLUSIONS

There was no significant single-session effect. Results suggest that haemodialysis patients may be weaker and have reduced postural stability when compared to historical data on comparable undialysed patients. The study was logistically complex and would be difficult to expand using these methods, but the issues merit further consideration.

Influences on knee movement strategies during walking in persons with medial knee osteoarthritis

OBJECTIVE

To investigate the movement and muscle activation strategies during walking of individuals with medial knee osteoarthritis (OA) to determine the influence of quadriceps strength, medial knee laxity, limb alignment, and self-reported knee instability on knee motion.

METHODS

Twenty-eight persons with medial knee OA and 26 control subjects participated. Quadriceps strength, medial knee laxity, and limb alignment were measured. Knee instability (I(KOS) score) was assessed with the Activities of Daily Living Scale of the Knee Outcome Survey. Knee motion and muscle activation patterns were measured with motion analysis. Group differences were detected with independent samples t-tests and predictive relationships were determined with linear and hierarchical regression analyses.

RESULTS

Individuals with OA were weaker, had greater medial knee laxity, and had more varus alignment. The OA group used less knee motion and higher muscle co-contraction during weight acceptance and single-limb support. Quadriceps strength and I(KOS) score significantly strengthened the prediction of knee motion during weight acceptance and single-limb support, whereas limb alignment and medial laxity did not.

CONCLUSION

The knee stiffening and higher muscle co-contraction used by the OA group may be detrimental to joint integrity. I(KOS) scores predicted knee motion after accounting for quadriceps strength, underscoring the importance of addressing knee instability with appropriate rehabilitation strategies in persons with medial knee OA in order to promote long-term joint integrity.

The effect of physiotherapy training programme on postural stability in men with hip osteoarthritis

This study presents the influence of a physiotherapy training programme over the standing balance in elderly hip osteoarthritis (OA) patients. The aim of this study was to analyse the standing balance in elderly male hip OA patients, and to investigate how the physiotherapy training programme could significantly improve the balance. The tests were performed on a group of selected OA patients as well as on a group of age- and sex-matched healthy control subjects before and after the physiotherapy training programme. The significant differences were observed between the results of tests performed before and after the physiotherapy training programme, and also between the hip OA patients and the control subjects in all CPF parameters, in both sagittal and frontal planes. In conclusion, the hip OA has an effect on the process of maintaining the standing balance. Moreover the physiotherapy training programme significantly improves the postural stability in male hip OA patients.

Risk factors for fracture in nonosteoporotic men and women

CONTEXT AND OBJECTIVE

It is not known which factors are associated with fracture in nonosteoporotic elderly. The aim of this study was to assess the association between fall-related risk factors and fracture risk in men and women without osteoporosis.

DESIGN

This study was part of the ongoing Dubbo Osteoporosis Epidemiology Study, which was designed as a prospective population-based cohort investigation.

PARTICIPANTS

At baseline, 924 women and 723 men aged 60+ yr did not have osteoporosis [bone mineral density (BMD) T-scores > -2.5]. The individuals have been followed for up to 15 yr.

MAIN OUTCOME MEASURES

Atraumatic fractures were prospectively identified through radiologists' reports.

RISK FACTORS

At baseline, femoral neck BMD (FNBMD) was measured by dual energy x-ray absorptiometry (DXA); history of fall, postural stability, and quadriceps strength was obtained.

RESULTS

During the follow-up period, among the nonosteoporotic group, 221 women and 105 men had sustained a fracture, accounting for 55 and 74% of total fractures in the entire Dubbo Osteoporosis Epidemiology Study sample, respectively. The following factors were independent risk factors for any fracture: in women, age per sd (hazard ratio, 1.2; 95% CI, 1.0-1.3), postural sway per sd (1.1, 1.0-1.2), FNBMD per sd (1.6, 1.3-1.9), fall in the previous 12 months (2.1, 1.6-2.7), and prior fracture (1.8, 1.2-2.7); in men, age (1.4, 1.1-1.6), postural sway (1.2, 1.0-1.3), FNBMD (1.2, 1.0-1.5), and fall in the previous 12 months (1.9, 1.2-3.0). Exposure to at least one of the risk factors could account for 49% (women) and 39% (men) of any fractures in this population.

CONCLUSION

In nonosteoporotic elderly, the combination of low BMD, advancing age, fall during the last 12 months, and prior fracture could identify a subgroup of individuals with high risk of fracture.

Effects of Osteoarthritis and Fatigue on Proprioception of the Knee Joint

OBJECTIVE

To evaluate the impact of knee osteoarthritis (OA) and periarticular muscular fatigue on knee joint kinesthesia.

DESIGN

Cross-sectional study.

SETTING

A physical medicine and rehabilitation outpatient clinic.

PARTICIPANTS

Fifty patients with bilateral OA of the knee, and a control group of 30 age-matched healthy volunteers.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The Kellgren-Lawrence grading system was used to determine the radiographic severity of knee OA. The Lequesne index of severity for knee osteoarthritis was used for assessment of pain, kinesthesia was measured by determining angle reposition error at the knee joint using isokinetic dynamometry, and muscle strength was measured by isokinetic dynamometry.

RESULTS

Reposition errors did not differ between the patient and the control groups, nor did they differ between pre- and postexercise.

CONCLUSIONS

Mild-to-moderate OA of the knees does not affect reposition error. Fatigue produced by mild-to-moderate exercise also has no effect on reposition error.

Quadriceps femoris muscle voluntary isometric force production and relaxation characteristics before and 6 months after unilateral total knee arthroplasty in women

The purpose of the present prospective intervention study was to evaluate voluntary isometric force production, relaxation and activation capacity of the quadriceps femoris (QF) muscle before and 6 months after unilateral total knee arthroplasty (TKA). TKA was performed in ten women with primary knee osteoarthritis (OA) using the condylar endoprostheses. Isometric maximal voluntary contraction (MVC) force, rate of force development at 50% of MVC (RFD50) and their ratio to body mass, half-relaxation time (HRT) and voluntary activation (VA) of the QF muscle were recorded in patients for operated and non-operated leg before and 6 months after TKA. Established characteristics were compared with data on the dominant leg of ten age- and gender-matched controls. The clinical examination was performed using the Knee Society System (KSS) scores and pain intensity was assessed by visual analogue scale. MVC force in operated leg was lower (P < 0.05) before and 6 months after TKA as compared with the non-operated leg (31 and 32%, respectively) and controls (48 and 44%, respectively). Patients had lower (P < 0.05) VA of the QF muscle in operated leg 6 months after TKA as compared to controls. Significant increase (P < 0.05) of KSS clinical scores and the tendency for the increasing of explosive force production of QF muscle in the operated leg were observed 6 months after TKA (RFD50 was 60% lower before TKA and 40% lower 6 months after surgery as compared to controls). When compared with the preoperative value, HRT prolongation (P < 0.05) was noted 6 months after TKA in QF muscle of both legs in patients. Therefore, the present study confirmed that patients with knee OA had reduced force generation ability of QF muscle before TKA and the improvement of explosive force was noted 6 months after surgery.

Estudo comparativo entre a aplicação de crioterapia, cinesioterapia e ondas curtas no tratamento da osteoartrite de joelho

A osteoartrite é a forma mais prevalente de doença articular. Os agentes físicos como o gelo e o calor podem combater o processo álgico quando corretamente indicados e utilizados. O objetivo deste trabalho foi a comparação de protocolos de tratamento fisioterapêutico, que envolveram o uso de cinesioterapia, crioterapia e ondas curtas, em indivíduos com osteoartrite de joelho. Em um estudo randomizado prospectivo cego foram tratados 25 indivíduos (25 joelhos), de 58 a 78 anos. GRUPO A: cinesioterapia e ondas curtas (n=9). GRUPO B: cinesioterapia e gelo (n=6). GRUPO C: cinesioterapia (grupo controle) (n=9). As variáveis analisadas foram: percepção subjetiva de dor (Borg), qualidade funcional (Lequesne), amplitude de movimento, flexibilidade e força muscular. A dor melhorou significativamente somente no grupo B, com qualidade funcional e flexibilidade positiva em todos grupos. O ganho de amplitude foi semelhante nos grupos B e C. Houve manutenção da força flexora nos grupos A e B e ganho nos indivíduos do grupo C. Na musculatura extensora observou-se ganho de força no grupo B e C e perda no grupo A. O melhor protocolo foi aquele que envolveu a aplicação de gelo e cinesioterapia para analgesia; não houve relação de ganho de amplitude, flexibilidade e força associado a termoterapia.

Lower leg muscle atrophy in ankle osteoarthritis

The aim of this study was to determine changes in the lower leg muscles associated with ankle osteoarthritis. Fifteen unilateral ankle osteoarthritis patients and fifteen age-gender-matched normal subjects were assessed with clinical [osteoarthritis latency time, pain, alignment, AOFAS ankle score, ankle range of motion (ROM), calf circumference], radiological (ankle osteoarthritis grading), and muscular-physiological parameters [isometric maximal voluntary ankle torque, surface electromyography of the anterior tibial (AT), medial gastrocnemius (MG), soleus (SO), and peroneus longus (PL) muscle]. The osteoarthritis patients had increased pain (6.8 points) and reduced AOFAS score (33.7 points) compared to the control group. Compared to the contralateral healthy leg, the arthritic leg showed reduced mean dorsi-/plantar flexion ROM (16.0 degrees), reduced mean calf circumference (2.1 cm), smaller mean dorsiflexion (16.4 Nm) and plantar flexion (15.8 Nm) torques, lower mean electromyography frequency for all muscles (AT -22.6 Hz; MG -27.3 Hz; SO -25.9 Hz; PL -28.5 Hz), and lower mean electromyography intensity in the AT [-28.0x10(3) (microv)2], MG [-13.3x10(3) (microv)2], and PL [-12.8x10(3) (microv)2]. SO mean electromyography intensity was not significantly changed [+2.0x10(3) (microv)2]. Unilateral ankle osteoarthritis is associated with atrophic changes of the lower leg muscles. This study supports previous observations on muscle dysfunction in knee osteoarthritis.

Musculoskeletal disorders associated with obesity: a biomechanical perspective

Despite the multifactorial nature of musculoskeletal disease, obesity consistently emerges as a key and potentially modifiable risk factor in the onset and progression of musculoskeletal conditions of the hip, knee, ankle, foot and shoulder. To date, the majority of research has focused on the impact of obesity on bone and joint disorders, such as the risk of fracture and osteoarthritis. However, emerging evidence indicates that obesity may also have a profound effect on soft-tissue structures, such as tendon, fascia and cartilage. Although the mechanism remains unclear, the functional and structural limitations imposed by the additional loading of the locomotor system in obesity have been almost universally accepted to produce aberrant mechanics during locomotor tasks, thereby unduly raising stress within connective-tissue structures and the potential for musculoskeletal injury. While such mechanical theories abound, there is surprisingly little scientific evidence directly linking musculoskeletal injury to altered biomechanics in the obese. For the most part, even the biomechanical effects of obesity on the locomotor system remain unknown. Given the global increase in obesity and the rapid rise in musculoskeletal disorders, there is a need to determine the physical consequences of continued repetitive loading of major structures of the locomotor system in the obese and to establish how obesity may interact with other factors to potentially increase the risk of musculoskeletal disease.

Increasing postural sway in rural-community-dwelling elderly persons with knee osteoarthritis

BACKGROUND

The purpose of this study was to clarify the influence of pain and radiographic findings of osteoarthritis (OA) of the knee on postural stability in rural-community-dwelling elderly persons.

METHODS

A total of 314 participants, consisting of 98 men and 216 women, aged 55 to 83 years, were investigated. Subjects were classified into four groups according to the symptoms and radiographic findings: Normal; Pain (pain without radiographic OA); Asymptomatic OA (radiographic OA without pain); Symptomatic OA (pain with radiographic OA). Knee pain was defined as unilateral or bilateral pain of the knee that had persisted for more than 1 month. Radiographic OA was defined as grades 2-4 according to the Kellgren and Lawrence criteria. The movement of the center of pressure (COP) was measured using a force platform to quantify postural sway.

RESULTS

Among the men, subjects in the Asymptomatic and Symptomatic OA groups showed higher values of the envelopment area tracing by the movement of the COP (E AREA) and the distance of the movement of the COP per second (LNG/TIME) under closed-eyes condition. Among the women, subjects in the Asymptomatic and Symptomatic OA groups showed higher values of E AREA and LNG/TIME under both open- and closed-eyes conditions. In the regression models consisting of the variables pain and radiographic OA, all estimates for pain were less than zero in both sexes. The value was significant only on the E AREA under closed-eyes conditions in women. On the other hand, all estimates for radiographic OA were higher than zero for both sexes. These values were significant for E AREA and LNG/TIME under open-eyes conditions in women, and E AREA and LNG/TIME under closed-eyes conditions in both sexes.

CONCLUSIONS

Subjects with OA showed greater postural sway than those without it. Only radiographic OA was a significant factor for increasing postural sway.

Hyaluronate improves pain, physical function and balance in the geriatric osteoarthritic knee: a 6-month follow-up study using clinical tests

OBJECTIVE

To investigate the effects of intraarticular hyaluronic acid (HA) (Artzal, Seikagaku Corp., Japan) in geriatric participants with unilateral knee osteoarthritis (OA).

METHOD

This was a prospective, observer-blind study with 6 months follow-up done in the setting of an outpatient rehabilitation department in a university-affiliated tertiary care medical center. Sixty-eight patients, aged 65 years or above, with symptoms and radiographic evidence of unilateral knee OA for at least 6 months were recruited. Patients received five weekly intraarticular injections of Artzal into symptomatic knees. Fifty-six participants completed the study. Fifty age-, body mass- and gender-matched healthy individuals were selected as control. Visual analog scale (VAS), Lequesne index and four balance tests including single-leg stance test (SLS), function reach test (FRT), timed "Up-and-Go" test (TUG) and Berg balance scale (BBS) were assessed before injection and at each follow-up visit in the OA group. Four balance tests were obtained on healthy participants for data comparison.

RESULTS

Before Artzal injections, the OA group showed significantly worse VAS, Lequesne index and four balance tests scores than did the control group (P < 0.001). Significant improvement in all outcome measures were noted at 1 week, 1, 3 and 6 months post the fifth injection compared with baseline before injection. Local adverse events were reported in four patients (7.1%).

CONCLUSION

Significant improvement in pain, physical function and balance tests was demonstrated after five weekly Artzal injections in geriatric patients with knee OA. The effect had rapid onset at 1 week and may last for 6 months.

Relative impact of radiographic osteoarthritis and pain on quadriceps strength, proprioception, static postural sway and lower limb function

OBJECTIVE

To investigate the relative impact of radiographic osteoarthritis (ROA) and current knee pain on lower limb physical function, quadriceps strength, knee joint proprioception, and postural sway.

METHODS

Using a 2x2 factorial design, 142 community derived subjects aged over 45 were divided into four subgroups based on the presence or absence of ROA (Kellgren & Lawrence>grade 2) and knee pain (as assessed by NHANES questions and a 100 mm visual analogue scale). Maximum isometric contraction of the quadriceps, knee joint proprioceptive acuity, static postural sway, and WOMAC index (both whole and function subscale) were assessed in all subjects.

RESULTS

Compared with normal subjects, reported disability was greater for all other subgroups (p<0.01). Subjects with both ROA and knee pain reported the greatest disability, and those with knee pain only had greater disability than those with ROA only. Quadriceps weakness was observed in all groups compared with normal subjects (p<0.01), though they were no significant intergroup differences. Subjects with knee pain had a greater sway area than those without (p<0.05) but the presence of ROA was not associated with increased postural sway. No differences in proprioceptive acuity were observed between groups.

CONCLUSIONS

The presence of knee pain has a negative association with quadriceps strength, postural sway, and disability compared with ROA. However, the presence of pain-free ROA has a significant negative influence on relative quadriceps strength and reported disability.

Is there an alternative to the full-leg radiograph for determining knee joint alignment in osteoarthritis?

OBJECTIVE

To assess the concurrent validity of alternative measures of frontal plane knee alignment, namely the radiographic anatomic axis and 5 clinical measures, in medial compartment knee osteoarthritis (OA) as compared with the mechanical axis on radiograph.

METHODS

Forty individuals (mean +/- SD age 64.7 +/- 9.4 years) with symptomatic medial knee OA participated. Knee alignment was measured according to the following methods: lower-limb mechanical axis on radiograph, lower-limb anatomic axis on radiograph, visual observation, distance between medial knee joint lines or medial malleoli using a caliper, distance between a plumb line and medial knee joint line or malleolus using a caliper, tibial alignment using a gravity inclinometer, and lower-limb alignment using a goniometer. Data were analyzed using Pearson's correlation coefficient or Spearman's rho correlation coefficient and simple linear regression.

RESULTS

The anatomic axis best correlated with the mechanical axis (r = 0.88), followed closely by the inclinometer method (r = 0.80). Other clinical measures of alignment that were significantly associated with the mechanical axis were the caliper method, the plumb-line method, and visual observation (r = 0.76, 0.71, and -0.52, respectively). However, the goniometer method failed to correlate.

CONCLUSION

The anatomic axis on radiograph and the inclinometer method appear to be valid alternatives to the mechanical axis on full-leg radiograph for determining frontal plane knee alignment in medial knee OA. These alternative methods of measuring knee alignment may increase the assessment of this parameter by clinicians and researchers alike, given that malalignment is an important indicator of disease progression and treatment outcome.

Postural control in male patients with hip osteoarthritis

Earlier studies have demonstrated that postural control is worse in patients with knee osteoarthritis (OA) than in control subjects, whereas little information is available about the postural control in patients with hip OA. The aim of this study was to investigate the standing balance in different test conditions in men with hip OA and to compare the results with those of age- and sex-matched healthy controls. Twenty-seven volunteers 47-64-year-old men with hip OA and 30 randomly selected, healthy age-matched men were tested using the sensory organisation test (SOT). The center point of force velocity (CPFV (cm/s)) was also determined during one- and two-footed standing. There was no difference between the patients and controls in the SOT test, in the strategy analysis or during one-footed standing. There were no significant differences in CPFV values between the better and worse hip side. Fatiguing exercise had no effect on two-footed CPFV with eyes open, but when the eyes were closed both two and one-footed CPFV values were significantly increased (p<0.01-0.05) in both groups. No differences were found in fatiguing exercise between control and OA subjects with eyes open or closed or in one-footed trials. In OA patient's subjective pain was related to increasing CPFV (p<0.05). In conclusion, the hip OA had no effect on static balance in men.

Exercise as a treatment for osteoarthritis

PURPOSE OF REVIEW

This review highlights recent important research, future directions, and clinical applications for exercise and osteoarthritis. It focuses on knee osteoarthritis because of its prevalence and the dearth of research involving other joint osteoarthritis. The review covers exercise prescription for symptomatic relief, and its potential role in reducing development and slowing progression of osteoarthritis.

RECENT FINDINGS

Meta-analyses support recommendations that exercise is important in osteoarthritis management. Benefits appear to be additive when exercise is delivered with other interventions such as weight loss. Mode of exercise delivery has cost implications and may influence overall outcome. It appears that supervised exercise sessions are superior to home exercises for pain reduction. The challenge remains to increase the proportion of patients exercising. Areas of emerging interest are exercise to prevent disease or slow its progression and recognition of patient subgroups that may respond differently to treatment. Based on studies showing a relation between weaker quadriceps strength and increased risk of developing knee osteoarthritis, particularly in women, strength training may be able to prevent knee osteoarthritis. Novel exercise programs that strengthen hip muscles or alter impairments in knee neuromuscular control may also influence disease progression.

SUMMARY

Future studies must identify cost-effective exercise modes, strategies to maximize exercise compliance and optimal treatment combinations. The role of muscle strength and altered neuromuscular control in the prevention and development of osteoarthritis must be evaluated with the view to devising and testing novel exercise interventions.

A multi-station proprioceptive exercise program in patients with bilateral knee osteoarthrosis: functional capacity, pain and sensoriomotor function. A randomized controlled trial

We investigated the effects of a multi-station proprioceptive exercise program on functional capacity, perceived knee pain, and sensoriomotor function. Twenty-two patients (aged 41-75 years) with grade 2-3 bilateral knee osteoarthrosis were randomly assigned to two groups: treatment (TR; n = 12) and non-treatment (NONTR; n = 10). TR performed 11 different balance/coordination and proprioception exercises, twice a week for 6 weeks. Functional capacity and perceived knee pain during rest and physical activity was measured. Also knee position sense, kinaesthesia, postural control, isometric and isokinetic knee strength (at 60, 120 and 180°·s(-1)) measures were taken at baseline and after 6 weeks of training. There was no significant difference in any of the tested variables between TR and NONTR before the intervention period. In TR perceived knee pain during daily activities and functional tests was lessened following the exercise program (p < 0.05). Perceived knee pain was also lower in TR vs. NONTR after training (p < 0.05). The time for rising from a chair, stair climbing and descending improved in TR (p < 0.05) and these values were faster compared with NONTR after training (p < 0.05). Joint position sense (degrees) for active and passive tests and for weight bearing tests improved in TR (p < 0.05) and the values were lower compared with NONTR after training (p < 0.05). Postural control ('eyes closed') also improved for single leg and tandem tests in TR (p < 0.01) and these values were higher compared with NONTR after training. The isometric quadriceps strength of TR improved (p < 0.05) but the values were not significantly different compared with NONTR after training. There was no change in isokinetic strength for TR and NONTR after the training period. The results suggest that using a multi-station proprioceptive exercise program it is possible to improve postural control, functional capacity and decrease perceived knee pain in patients with bilateral knee osteoarthrosis. Key PointsIt is possible to improve postural control, functional capacity and decrease perceived knee pain in patients with bilateral knee osteoarthrosis with a pure proprioceptive/ balance exercise program used in the present study.The exercise regime used in the present study was as effective as previous studies, but of much shorter duration and utilized unsophisticated, inexpensive equipment which is available in most physiotherapy departments.Therefore, the incorporation of this exercise program into clinical practice is readily feasible.

Identification of high-risk individuals for hip fracture: a 14-year prospective study

In this 14-year prospective study, men and women were found to share a common set of risk factors for hip fracture: low BMD, postural instability and/or quadriceps weakness, a history of falls, and prior fracture. The combination of these risk factors accounted for 57% and 37% of hip fractures in women and men, respectively.

INTRODUCTION

Risk factors for hip fracture, including low BMD, identified in women, have not been shown to be useful in men. It is also not known whether fall-related factors (muscle strength and postural instability) predict hip fracture. This study examined the association between falls-related factors and hip fractures in elderly men and women.

MATERIALS AND METHODS

This is an epidemiologic, community-based prospective study, which included 960 women and 689 men > or = 60 years of age who have been followed for a median of 12 years (interquartile range, 6-13). The number of person-years was 9961 for women and 4463 for men. The outcome measure was incidence of hip fracture. Risk factors were femoral neck BMD (FNBMD), postural sway, quadriceps strength, prior fracture, and fall.

RESULTS

Between 1989 and 2003, 115 (86 women) sustained a hip fracture. The risk of hip fracture (as measured by hazards ratio [HR]) was increased by 3.6-fold (95% CI: 2.6-4.5) in women and 3.4-fold (95% CI: 2.5-4.6) in men for each SD (0.12 g/cm2) reduction in FNBMD. After adjusting for BMD, the risk of hip fracture was also increased in individuals with the highest tertile of postural sway (HR: 2.7; 95% CI: 1.6-4.5) and low tertiles of quadriceps strength (HR: 3.0; 95% CI: 1.3-6.8). Furthermore, a history of fall during the preceding 12 months and a history of fracture were independent predictors of hip fracture. For each level of BMD, the risk of hip fracture increased linearly with the number of non-BMD risk factors. Approximately 57% and 37% of hip fracture cases in women and men, respectively, were attributable to the presence of risk factors, osteoporosis (BMD T score < or = -2.5), and advancing age.

CONCLUSIONS

Men and women had a common set of risk factors for hip fracture: low BMD, postural instability and/or quadriceps weakness, a history of falls, and prior fracture. Preventive strategies should simultaneously target reducing falls and improvement of bone strength in both men and women.

Gender-Related Differences in Physical Performance among Seniors

This study examined gender differences in balance, gait, and muscle performance in seniors and identified gender-specific factors contributing to physical performance. Forty (20 men, 20 women) healthy, community-dwelling seniors (74.5 ± 5.3 years) participated. Limits of stability, gait speed, lower limb flexor and extensor isokinetic concentric peak torques, self-reported activity level, and balance confidence were measured. No gender differences were detected in gait speed, limits of stability when normalized to height, activity level, or balance confidence (p≥ .188). Women were weaker than men (p≤ .007), even after controlling for weight and body-mass index, suggesting that other gender-related factors contribute to strength. Gender accounted for 18–46% of the variance in strength and served as a modifier of the relationship between activity level and strength in some muscle groups. The primary factors relating to gender-specific strength was activity level in men and body weight in women.

Association between radiographic joint space narrowing, function, pain and muscle power in severe osteoarthritis of the knee

OBJECTIVE

To examine the association between radiographic classification of severe knee osteoarthritis and measurements of function, pain and power.

DESIGN

Cross-sectional study.

SETTING

Specialist orthopaedic hospital.

SUBJECTS

One hundred and twenty-three patients on the waiting list for elective knee arthroplasty.

OUTCOME MEASURES

Weight-bearing antero-posterior radiographs scored for severity of osteoarthritis using the Kellgren and Lawrence scale. Function measured using the function subscale of the WOMAC (Western Ontario and McMaster Universities) index, timed tests of walking speed and sit-to-stand. Pain measured using the pain subscale of the WOMAC index and a visual analogue scale. Extensor strength of the lower limb measured with the leg extensor power rig.

RESULTS

Within any radiographic grade there was considerable variation in function: WOMAC function for patients with grade 2 mean 64 (47-86), grade 3 mean 47 (12-89) grade 4 mean 45 (2-92). There was poor correlation between radiographic score function, pain or muscle power, with no statistically significant associations. A wide range of scores was also seen within patients with the same radiographic grade.

CONCLUSIONS

Radiographic score was not found to be closely associated with function. Amongst patients with the same radiographic score there was considerable variation in function, pain and power.

Neuromuscular quadriceps dysfunction prior to osteoarthritis of the knee

Decreased maximal quadriceps strength and voluntary activation has been observed in patients with osteoarthritis in previous studies, but those results do not allow any conclusions to be drawn as to whether quadriceps dysfunction precedes or follows osteoarthritis. Thirty-two patients (group a) who underwent partial meniscectomy 48+/-9 month prior to the study were matched according to their weight and body mass index with a control group (group b). The twitch interpolation technique was used to determine maximal voluntary contraction (MVC) and voluntary activation (VA) of the quadriceps muscle of both legs. Subjective assessment of the knee was performed using the Lysholm-Score. AP and lateral X-rays of the operated knee were obtained. None of the participants showed any evidence of characteristic radiological or clinical signs for osteoarthritis. A significantly lower MVC was noticed in both the affected and the contralateral knee of group a in comparison to group b (p < 0.01). The VA in group a yielded 80.9+/-15.4% for the injured side and 83.1+/-11.5% for the contralateral side, with no statistical difference (p = 0.18). The VA in group b was 89.4+/-5.8% for the right side and 88+/-6.8% for the left side both being significantly higher in comparison to group a. This study has shown, that patients following meniscus resection present with bilateral quadriceps weakness as already described in patients with manifest osteoarthritis. The authors hypothesise that muscle dysfunction may be an etiologic factor underlying the pathologic changes of osteoarthritis. Whether muscle dysfunction occurs also at other sites, e.g. in the upper extremity, remains unclear but would be of interest in order to detect a generalized neuromuscular dysfunction.

Association of sensorimotor function with knee joint kinematics during locomotion in knee osteoarthritis

OBJECTIVE

To evaluate the relationship between quadriceps sensorimotor function (knee joint-position sense, quadriceps strength, and quadriceps onset of activity) and knee joint kinematics (knee flexion at initial contact and loading) during level walking and stair descent in a large cohort of 220 people with knee osteoarthritis.

DESIGN

Cross-sectional correlational study.

RESULTS

Joint-position sense correlated with knee flexion at initial contact during both tasks (r = -0.20 and -0.14, P <0.05). Strength correlated with peak loading response knee flexion during both tasks (r = 0.17 and 0.20, P < 0.05). Quadriceps onset correlated with knee flexion at initial contact during stair descent (r = 0.14, P < 0.05). Furthermore, differences in kinematic variables were observed when participants were divided into those with best and worst sensorimotor function.

CONCLUSION

Impaired sensorimotor function as measured in this study is not strongly associated with altered knee joint kinematics observed in knee osteoarthritis patients during locomotion.

Quadriceps activation failure as a moderator of the relationship between quadriceps strength and physical function in individuals with knee osteoarthritis

OBJECTIVE

To determine if quadriceps activation failure (QAF) moderates the relationship between quadriceps strength and physical function in individuals with knee osteoarthritis (OA).

METHODS

Quadriceps strength and QAF were measured in 105 subjects (80 females) with radiographically confirmed knee OA using a burst-superimposition maximum voluntary isometric quadriceps torque test procedure. Subjects performed the Get Up and Go test as a physical performance measure of function and completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) as a self-report measure of function. A principal component analysis was performed to combine the Get Up and Go score and the WOMAC subscores into a single function score. Hierarchical regression analysis was performed to examine the ability of 3 models to predict physical function (strength = function; strength + QAF = function; strength + QAF + [strength x QAF] = function). Partial F tests were used to compare differences in R(2) values between each model.

RESULTS

Each model independently predicted the principal component score for function. Adding the strength x QAF interaction term with strength to the model resulted in the highest prediction of function. The strength x QAF interaction indicated that subjects with lower levels of quadriceps strength and higher levels of QAF had lower levels of function than those with comparable levels of weakness but low levels of QAF.

CONCLUSION

The magnitude of QAF serves to moderate the relationship between quadriceps strength and physical function. Physical function may be more severely affected by weakness of the quadriceps muscles in individuals with knee OA who have higher degrees of QAF than those who may have quadriceps weakness, but do not have QAF.

Quadriceps femoris muscle weakness and activation failure in patients with symptomatic knee osteoarthritis

PURPOSE

Quadriceps weakness is common in patients with knee osteoarthritis (OA), and has been attributed to failure of voluntary activation. Methodological differences may have contributed to previous reports of extensive failure of voluntary activation in patients with osteoarthritis. The purpose of this study was to determine the extent of quadriceps muscle weakness and activation failure in middle aged patients with symptomatic medial knee osteoarthritis using maximum voluntary isometric contractions (MVIC) and a burst superimposition technique.

METHODS

Measurements of quadriceps MVIC and extent of voluntary activation were made in 12 subjects with knee OA and 12 similarly aged uninjured subjects. Voluntary activation was tested by superimposing a train of electrical stimulation on a maximal effort volitional contraction of the quadriceps muscle.

RESULTS

The group of subjects with knee OA had significantly less quadriceps strength relative to body mass index (BMI) than the group of control subjects (p=0.010). No difference in voluntary activation was observed (p=0.233), however, 50% of the OA group, and only 25% of the control group failed to fully activate the quadriceps.

DISCUSSION

The finding of quadriceps weakness is consistent with past literature. Providing adequate instruction, feedback, and several attempts to maximally contract the muscle likely yielded greater volitional activation (thus less activation failure) than had been reported previously. This finding has implications for the rehabilitation of weakened quadriceps in patients with knee osteoarthritis.

Does pre-operative physiotherapy improve outcomes from lower limb joint replacement surgery? A systematic review

A systematic review of randomised controlled trials was performed to evaluate the effectiveness of pre-operative physiotherapy programmes on outcome following lower limb joint replacement surgery. A search of relevant key terms was used to find suitable trials, with five papers meeting the inclusion criteria for the review. The methodological quality of the trials was rated using the PEDro scale. Estimates of the size of treatment effects were calculated for each outcome in each trial, with 95% confidence intervals calculated where sufficient data were provided. Of the three trials pertaining to total knee replacement, only very small mean differences were found between control and intervention groups for all of the outcome measures. Where confidence intervals could be calculated, these showed no clinically important differences between the groups. Two papers (one study) pertaining to total hip replacements found significant improvements in WOMAC scores, hip strength and range of movement, walking distance, cadence, and gait velocity for the intervention group, compared to a control group. Estimates of treatment effect sizes for these outcomes were larger than for the total knee replacement studies, with confidence intervals showing potentially clinically important differences between group means. However, as the intervention group also received an additional intensive post-operative physiotherapy program, these results cannot be attributed solely to the pre-operative program. This systematic review shows that pre-operative physiotherapy programmes are not effective in improving outcome after total knee replacement but their effect on outcome from total hip replacement cannot be adequately determined.

Relationship of knee joint proprioception to pain and disability in individuals with knee osteoarthritis

Proprioception plays an integral role in neuromotor control of the knee joint and deficits in knee joint proprioception are well documented in individuals with knee osteoarthritis (OA). However, the functional relevance of these deficits is not clear. This cross-sectional study evaluated the relationship between knee joint proprioception and pain and disability in a large cohort of individuals with knee OA. Two hundred and twenty participants (145 F, 75 M) with symptomatic knee OA were recruited from the community. Five non-weight bearing active tests with ipsilateral limb matching responses were performed at 20 degrees and 40 degrees flexion to measure knee joint position sense. Pain and disability were assessed by self-reported questionnaires and objective measures of balance and gait. Results showed little association between knee joint position sense variables and measures of pain and disability (r values <0.24, most p>0.05). When comparing participants with the worst and best joint position sense, no significant differences in pain and disability could be found (p>0.05). While our study design does not allow causality to be established, these results suggest that deficits in joint position sense may be due to factors other than pain and that deficits are not large enough to impact upon disability.

Improvement of voluntary quadriceps muscle activation after total knee arthroplasty

OBJECTIVE

To evaluate the maximal voluntary contraction (MVC) force and the voluntary activation of the quadriceps femoris muscle in patients with knee osteoarthritis (OA) before and after total knee arthroplasty (TKA).

DESIGN

A prospective intervention study.

SETTING

University hospital clinic in Germany.

PATIENTS

Fifty patients (32 women, 18 men; mean age +/- standard deviation, 65.8+/-5.6 y) with knee OA and 23 healthy age- and gender-matched control subjects.

INTERVENTION

Unilateral TKA without patella resurfacing.

MAIN OUTCOME MEASURES

Voluntary activation, MVC, and true maximal contraction forces of the bilateral quadriceps femoris muscles, using the twitch interpolation technique before and 33+/-8 months after TKA. Assessment of postoperative knee pain by the Lewis score.

RESULTS

Voluntary activation increased bilaterally after surgery (P<.01 operated side, P=.02 nonoperated side) but remained lower than the voluntary activation of the controls. MVC (P<.001) and true maximal contraction forces (P=.01) increased significantly on the operated side. MVC remained unchanged (P=.45), and true maximal contraction forces decreased significantly (P=.04) on the nonoperated side.

CONCLUSION

Patients with knee OA have significant bilateral voluntary activation deficits that are, at least in part, reversible within 3 years after TKA. Rehabilitation programs immediately after TKA should focus on reduction of voluntary activation deficits. After voluntary activation improves, physical therapy should target the augmentation of quadriceps femoris muscle strength.

Investigation of hip abductor activation in subjects with clinical unilateral hip osteoarthritis

OBJECTIVES

(a) To compare the magnitude of gluteus medius and tensor fascia lata activation between a group of subjects with clinical unilateral hip osteoarthritis and a group of healthy older adults. (b) To compare the magnitude of activation of the gluteus medius and tensor fascia lata between sides in a group of subjects with clinical unilateral hip osteoarthritis and a group of healthy older adults.

METHODS

19 subjects with clinical unilateral hip osteoarthritis and 19 healthy controls were investigated. The subjects performed a stepping task during which recordings were obtained using surface electromyograms from the hip abductors, and kinetic data were obtained from a dual force platform.

RESULTS

Subjects with clinical hip osteoarthritis had higher gluteus medius activation than the healthy older adults (p=0.037). In addition, there were no differences in the magnitude of gluteus medius activation between the sides (p=0.733). There was no difference in the force platform data between the groups (p=0.078).

CONCLUSIONS

The increased magnitude of gluteus medius activation in the group with hip osteoarthritis is evidence of a muscular dysfunction associated with hip disease. This has implications for the progressive nature of the disease and for its conservative management.