The role of muscle weakness in the pathogenesis of osteoarthritis

Self management, joint protection and exercises in hand osteoarthritis: a randomised controlled trial with cost effectiveness analyses

BACKGROUND

There is limited evidence for the clinical and cost effectiveness of occupational therapy (OT) approaches in the management of hand osteoarthritis (OA). Joint protection and hand exercises have been proposed by European guidelines, however the clinical and cost effectiveness of each intervention is unknown.This multicentre two-by-two factorial randomised controlled trial aims to address the following questions:• Is joint protection delivered by an OT more effective in reducing hand pain and disability than no joint protection in people with hand OA in primary care?• Are hand exercises delivered by an OT more effective in reducing hand pain and disability than no hand exercises in people with hand OA in primary care?• Which of the four management approaches explored within the study (leaflet and advice, joint protection, hand exercise, or joint protection and hand exercise combined) provides the most cost-effective use of health care resources

METHODS/DESIGN

Participants aged 50 years and over registered at three general practices in North Staffordshire and Cheshire will be mailed a health survey questionnaire (estimated mailing sample n = 9,500). Those fulfilling the eligibility criteria on the health survey questionnaire will be invited to attend a clinical assessment to assess for the presence of hand or thumb base OA using the ACR criteria. Eligible participants will be randomised to one of four groups: leaflet and advice; joint protection (looking after your joints); hand exercises; or joint protection and hand exercises combined (estimated n = 252). The primary outcome measure will be the OARSI/OMERACT responder criteria combining hand pain and disability (measured using the AUSCAN) and global improvement, 6 months post-randomisation. Secondary outcomes will also be collected for example pain, functional limitation and quality of life. Outcomes will be collected at baseline and 3, 6 and 12 months post-randomisation. The main analysis will be on an intention to treat basis and will assess the clinical and cost effectiveness of joint protection and hand exercises for managing hand OA.

DISCUSSION

The findings will improve the cost-effective evidence based management of hand OA.

TRIAL REGISTRATION

identifier: ISRCTN33870549.

Effect of knee position on quadriceps muscle force steadiness and activation strategies

INTRODUCTION

In this study we investigated the effect of knee position on quadriceps force steadiness and activation strategies.

METHODS

Quadriceps force steadiness was evaluated in 22 volunteers at two knee positions by testing their ability to regulate submaximal force. Muscle activation strategies were studied in both time and frequency domains using surface electromyography.

RESULTS

Quadriceps force fluctuations and the associated agonist and antagonist activity were significantly higher at 90° than at 30° of flexion (P < 0.05). The quadriceps median frequency recorded at 30° was significantly higher than at 90° of flexion (P < 0.05). Regression analyses revealed that force steadiness was related to quadriceps activation and median frequency (P < 0.001), but not to hamstring coactivation (P > 0.05).

CONCLUSIONS

The results indicate that knee position significantly affects quadriceps force steadiness and activation strategies. This finding may have important implications for designing a force control testing protocol and interpreting test results.

Quadriceps muscle activation and radiographic osteoarthritis following ACL revision

PURPOSE

Quadriceps strength and activation may play an important role in the recovery from ACL revision surgery. The purpose of this study was to describe quadriceps strength and central activation ratio (CAR) and correlate with radiographic findings in patients with ACL revision surgery.

METHODS

Twenty-one patients who were on average 47.5 ± 21.1 months [range: 14-85 months] post-revision ACL reconstruction. We performed knee joint physical examination and radiographic evaluation. Quadriceps strength testing consisted of maximal voluntary isometric contractions (MVIC) with the knee bent to 90-degrees bilaterally. We calculated quadriceps central activation ratio using the superimposed burst technique. Radiographs (bilateral standing antero-posterior in knee flexion and lateral in full extension) were evaluated by a fellowship-trained orthopedic surgeon using the International Knee Documentation Committee (IKDC) grading system.

RESULTS

Mean CAR was 83.9 ± 12.0% on the reconstructed limb and 85.5 ± 9.5% on the contralateral limb. Average, normalized MVIC torque was 2.5 ± 1.0 Nm/kg on the reconstructed limb and 2.7 ± 1.0 N m/kg for the contralateral limb. Patient age at the time of follow-up evaluation was related to severity of knee joint degeneration, particularly the medial, anterior and patellofemoral compartments. Younger patients with lower CARs tended to have more severe degeneration in the patellofemoral joint. Older patients with lower normalized MVIC torque values tended to exhibit more severely graded degeneration in the patellofemoral joint.

CONCLUSION

Bilateral quadriceps central activation deficits and radiographic osteoarthritis are evident in patients with revision ACL reconstruction.

Does electric stimulation of the vastus medialis muscle influence rehabilitation after total knee replacement?

Patients with knee osteoarthritis present with reduced quadriceps muscle strength, which is partially responsible for impaired function and disability. Although total knee replacement (TKR) is an effective surgical procedure, residual muscle weakness is not usually addressed and may persist for years postoperatively. This article reports the results of a prospective, randomized, controlled trial evaluating the effect of electric muscle stimulation of the vastus medialis on the speed and effort of walking, quality of life, and knee performance in patients undergoing TKR. Seventy patients who underwent TKR were randomly divided into 2 groups. Patients in group A received electric muscle stimulation and standard physiotherapy for 6 weeks, while patients in group B received physiotherapy only. All patients were assessed with both subjective and objective clinical scales preoperatively and at 6, 12, and 52 weeks postoperatively. Patients in group A demonstrated a statistically significant increase in walking speed, Oxford Knee Score, and American Knee Society function score compared to those in group B at 6 weeks (P=.003, .001, and .001, respectively) and at 12 weeks (all P=.001). A statistically significant increase in the SF-36 physical component summary score was observed at 6, 12, and 52 weeks (all P=.001). Three patients found the sensation of the electrical stimulation uncomfortable and abandoned its use. No skin reactions and surgical site infections were observed. Electrical stimulation of the vastus medialis muscle in addition to conventional physiotherapy improves functional recovery and early rehabilitation after TKR.

Effect of quadriceps strength and proprioception on risk for knee osteoarthritis

PURPOSE

Impaired quadriceps strength and joint position sense (JPS) have been linked with knee osteoarthritis (OA) cross-sectionally. Although neither has been independently associated with incident radiographic OA, their combination may mediate risk. The purpose of this study was to determine whether better sensorimotor function protects against the development of incident radiographic or symptomatic knee OA.

METHODS

The Multicenter Osteoarthritis study is a longitudinal study of adults aged 50–79 yr at high risk for knee OA. Participants underwent bilateral, weight-bearing, fixed-flexion radiographs, JPS acuity tests, and isokinetic quadriceps strength tests. The relationships between combinations of the tertiles of sex-specific baseline peak strength and mean JPS and development of incident radiographic (Kellgren–Lawrence (KL) grade Q2) or symptomatic knee OA (KL grade Q2 and frequent knee pain or stiffness) at a 30-month follow-up were evaluated. Secondary analyses defined JPS as the variance during the 10 JPS trials and also assessed the interaction of strength and JPS in predicting each outcome.

RESULTS

The study of incident radiographic knee OA included 1390 participants (age = 61.2 ± 7 .9 yr and body mass index = 29.4 ± 5.1 kg·m−²), and the study of incident symptomatic knee OA included 1829 participants (age = 62.2 ± 8.0 yr and body mass index = 30.0 ± 5.4 kg·m−²). Greater strength at baseline protected against incident symptomatic but not radiographic knee OA regardless of JPS tertile. There was no significant relationship between the strength–JPS interaction and the development of radiographic or symptomatic knee OA.

CONCLUSIONS

The finding that quadriceps strength protected against incident symptomatic but not radiographic knee OA regardless of JPS tertile suggests that strength may be more important than JPS in mediating risk for knee OA.

Quadriceps activation following knee injuries: a systematic review

CONTEXT

Arthrogenic muscle inhibition is an important underlying factor in persistent quadriceps muscle weakness after knee injury or surgery.

OBJECTIVE

To determine the magnitude and prevalence of volitional quadriceps activation deficits after knee injury.

DATA SOURCES

Web of Science database.

STUDY SELECTION

Eligible studies involved human participants and measured quadriceps activation using either twitch interpolation or burst superimposition on patients with knee injuries or surgeries such as anterior cruciate ligament deficiency (ACLd), anterior cruciate ligament reconstruction (ACLr), and anterior knee pain (AKP).

DATA EXTRACTION

Means, measures of variability, and prevalence of quadriceps activation (QA) failure (<95%) were recorded for experiments involving ACLd (10), ACLr (5), and AKP (3).

DATA SYNTHESIS

A total of 21 data sets from 18 studies were initially identified. Data from 3 studies (1 paper reporting data for both ACLd and ACLr, 1 on AKP, and the postarthroscopy paper) were excluded from the primary analyses because only graphical data were reported. Of the remaining 17 data sets (from 15 studies), weighted mean QA in 352 ACLd patients was 87.3% on the involved side, 89.1% on the uninvolved side, and 91% in control participants. The QA failure prevalence ranged from 0% to 100%. Weighted mean QA in 99 total ACLr patients was 89.2% on the involved side, 84% on the uninvolved side, and 98.5% for the control group, with prevalence ranging from 0% to 71%. Thirty-eight patients with AKP averaged 78.6% on the involved side and 77.7% on the contralateral side. Bilateral QA failure was commonly reported in patients.

CONCLUSIONS

Quadriceps activation failure is common in patients with ACLd, ACLr, and AKP and is often observed bilaterally.

Prehabilitation versus usual care before total knee arthroplasty: A case report comparing outcomes within the same individual

This case report compared pre- and postoperative functional ability, knee strength, and pain of a female who underwent two separate total knee arthroplasty (TKA) procedures. The female patient was part of a larger research study. The first surgery on the right knee was preceded with usual care and the second surgery on the left knee was preceded by prehabilitation. Functional ability was assessed by a 6-minute walk, chair raises, and the time required to ascend and descend stairs. Knee extension and flexion isokinetic strength was assessed using the KinCom Isokinetic Dynamometer. Pain was assessed using the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC). Functional abilities, knee strength, and pain were assessed at baseline measurements 4 weeks before surgery, 1 week before surgery, and at 1 and 3 months post surgery during each TKA procedure. Results indicate that the prehabilitation intervention had a favorable impact on improving functional ability up to 30%, increasing knee strength by 50% and decreasing pain prior to the left knee TKA. For this patient, prehabilitation increased functional ability and strength prior to surgery. Gains in strength were maintained in the nonsurgical knee after surgery. These findings indicate that prehabilitation may be effective at facilitating the rehabilitation following a TKA.

Do worsening knee radiographs mean greater chances of severe functional limitation?

OBJECTIVE

Development of functional limitation is thought to be unrelated to changes in severity of radiographic osteoarthritis (OA) of the knee. We evaluated the relationship of change in radiographic OA to the incidence of severe functional limitation.

METHODS

Participants of the Multicenter Osteoarthritis Study, a cohort study of persons with or at high risk of knee OA, were evaluated at 0 and 30 months. Subjects were classified as having no, incident, stable, or worsening radiographic OA. Incidence of severe functional limitation was defined by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function scores (≥36.1/68) and walking speed (≤1.0 meter/second) at 30 months. The relationship of the change in radiographic OA to the incidence of severe functional limitation was evaluated by calculating risk ratios adjusted for potential confounders.

RESULTS

Of the 2,210 subjects included (mean age 62 years, mean body mass index 30 kg/m², 60% women), 53% had no, 6% had incident, 14% had stable, and 27% had worsening radiographic OA. Persons with incident radiographic OA had 1.9 and 1.8 times the risk by WOMAC physical function score and walking speed, respectively, to have incident severe functional limitation compared with those with no radiographic OA over 30 months. Compared with those with stable radiographic OA, persons with worsening radiographic OA had 2.2 and 2.3 times the risk of incident severe functional limitation, respectively.

CONCLUSION

Changes in structural disease are associated with the development of severe functional limitations in persons with or even at high risk of knee OA.

The effects of a non-operative multimodal programme on osteoarthritis of the knee

INTRODUCTION

The purpose of this study was to determine if a multimodal programme including physiotherapy and education could improve the symptoms of osteoarthritis of the knee across various severities of disease.

PATIENTS AND METHODS

Seventy-two patients with osteoarthritis of the knee confirmed on radiographic evidence were referred over a 13-month period for a lower limb programme which consisted of 12 classes over 6 weeks of group physiotherapy and included education on osteoarthritis, diet and exercise. Six patients went on to have joint arthroplasty at a mean time of 6.5 months with three placed on the waiting list during follow-up.

RESULTS

Pre-intervention, the mean WOMAC score was 42.0 and the mean Oxford Knee Score was 32.8. Post-intervention at a mean follow-up of 12 months, the mean WOMAC score was 31.6 and the mean Oxford Knee Score 24.3. The change in scores following intervention was statistically significant (P < 0.01). Using the WOMAC scoring system, the greatest effect size was seen in patients with Kellgren–Lawrence grade IV whilst using the Oxford knee scoring system, the greatest effect size was seen in patients with Kellgren–Lawrence grade II.

CONCLUSIONS

At 12 months, a multimodal programme of non-operative interventions has an excellent impact upon the symptoms of osteoarthritis of the knee with improved patient-reported scores. The level of improvement cannot be inferred from the radiographic grade of osteoarthritis. This modality could be considered for all patients with mild-to-moderate osteoarthritis of the knee.

Quadriceps and hamstrings muscle dysfunction after total knee arthroplasty

BACKGROUND/RATIONALE

Although TKA reliably reduces pain from knee osteoarthritis, full recovery of muscle strength and physical function to normal levels is rare. We presumed that a better understanding of acute changes in hamstrings and quadriceps muscle performance would allow us to enhance early rehabilitation after TKA and improve long-term function.

QUESTIONS/PURPOSES

The purposes of this study were to (1) evaluate postoperative quadriceps and hamstrings muscle strength loss after TKA and subsequent recovery using the nonoperative legs and healthy control legs for comparison, and (2) measure hamstrings coactivation before and after TKA during a maximal isometric quadriceps muscle contraction and compare with nonoperative and healthy control legs.

METHODS

We prospectively followed 30 patients undergoing TKA at 2 weeks preoperatively and 1, 3, and 6 months postoperatively and compared patient outcomes with a cross-sectional cohort of 15 healthy older adults. Bilateral, isometric strength of the quadriceps and hamstrings was assessed along with EMG measures of hamstrings coactivation during a maximal isometric quadriceps contraction.

RESULTS

There were no differences in strength loss or recovery between the quadriceps and hamstrings muscles of the operative leg throughout the followup, although differences existed when compared with nonoperative and healthy control legs. Hamstrings muscle coactivation in the operative leg during a maximal quadriceps effort was elevated at 1 month (144.5%) compared to the nonoperative leg.

CONCLUSIONS

Although quadriceps dysfunction after TKA typically is recognized and addressed in postoperative therapy protocols, hamstrings dysfunction also is present and should be addressed.

CLINICAL RELEVANCE

Quadriceps and hamstrings muscle strengthening should be the focus of future rehabilitation programs to optimize muscle function and long-term outcomes.

Postural control and thigh muscle activity in men with knee osteoarthritis

The aim of this study was to examine the standing balance and the function of vastus medialis (VM) and biceps femoris (BF) muscles with surface electromyography (EMG). Fifty-four subjects with uni- or bilateral knee osteoarthritis (OA) (aged 50-69 years) and 53 age-matched randomly selected clinically and radiologically healthy men participated in this study. Postural control was assessed on a force platform with a bipedal stance with eyes open (EO) and closed (EC) and a monopedal stance with EO. The balance parameters, mean sway velocity, velocity along AP and ML axes, elliptical area, standard deviation of center of pressure, average radial displacement, mean frequency and frequency domain balance parameters and different power spectral density frequency bands were determined. Root mean square (RMS) for EMG amplitude, mean EMG frequency (f(EMG,mean)) and median EMG frequency (f(EMG,med)) of motor unit activity were calculated from the normalized EMG data. During bipedal stance with EC and EO, there were no significant differences in balance parameters between groups, but during bipedal stance with EO, the RMS in VM was about 56% higher (p<0.05) in subjects with knee OA than in the control subjects and the values of f(EMG,mean) and f(EMG,med) were about 48% higher (p<0.05) in control subjects than subjects with knee OA. It is concluded that subjects with knee OA do not have any standing balance deficit, but they do exhibit increased muscle activity in VM muscle compared to control subjects.

Quadriceps weakness predicts risk for knee joint space narrowing in women in the MOST cohort

OBJECTIVE

Quadriceps weakness has been reported with incident but not progressive knee osteoarthritis (OA) in longitudinal studies. This study examined the relationship between quadriceps strength and worsening of knee joint space narrowing (JSN) over 30 months.

METHODS

Longitudinal, observational study of adults aged 50-79 years with OARSI JSN score <3 at baseline. Baseline measures included bilateral weight-bearing fixed flexion radiographs, isokinetic concentric quadriceps and hamstring strength, height and weight, and physical activity. Hamstring:quadriceps (H:Q) strength ratios also were evaluated. Worsening was defined as an increase in JSN score in the tibiofemoral and/or patellofemoral compartments on 30-month radiographs or total knee replacement. Knee-based analyses used generalized estimating equations, stratified by sex, to assess relationships between strength and knee JSN while controlling for covariance between knees within subjects as well as age, body mass index (BMI), history of knee injury and/or surgery, physical activity level and alignment.

RESULTS

3856 knees (2254 females and 1602 males) with JSN score <3 at baseline and no missing follow-up data were included. Mean+/-SD age was 62.2+/-7.7 in women and 61.6+/-8.1 in men. Women in the lowest tertile of quadriceps strength had an increased risk of whole knee JSN (OR=1.66, 95% CI=1.26, 2.19) and tibiofemoral JSN (OR=1.69, 95% CI=1.26, 2.28). However, no associations were found between strength and JSN in men or H:Q<0.6 and JSN in men or women.

CONCLUSIONS

In women but not in men, quadriceps weakness was associated with increased risk for tibiofemoral and whole knee JSN.

The effects of a non-operative multimodal programme on osteoarthritis of the knee

INTRODUCTION

The purpose of this study was to determine if a multimodal programme including physiotherapy and education could improve the symptoms of osteoarthritis of the knee across various severities of disease.

PATIENTS AND METHODS

Seventy-two patients with osteoarthritis of the knee confirmed on radiographic evidence were referred over a 13-month period for a lower limb programme which consisted of 12 classes over 6 weeks of group physiotherapy and included education on osteoarthritis, diet and exercise. Six patients went on to have joint arthroplasty at a mean time of 6.5 months with three placed on the waiting list during follow-up.

RESULTS

Pre-intervention, the mean WOMAC score was 42.0 and the mean Oxford Knee Score was 32.8. Post-intervention at a mean follow-up of 12 months, the mean WOMAC score was 31.6 and the mean Oxford Knee Score 24.3. The change in scores following intervention was statistically significant (P < 0.01). Using the WOMAC scoring system, the greatest effect size was seen in patients with Kellgren-Lawrence grade IV whilst using the Oxford knee scoring system, the greatest effect size was seen in patients with Kellgren-Lawrence grade II.

CONCLUSIONS

At 12 months, a multimodal programme of non-operative interventions has an excellent impact upon the symptoms of osteoarthritis of the knee with improved patient-reported scores. The level of improvement cannot be inferred from the radiographic grade of osteoarthritis. This modality could be considered for all patients with mild-to-moderate osteoarthritis of the knee.

The effects of a non-operative multimodal programme on osteoarthritis of the knee

INTRODUCTION

The purpose of this study was to determine if a multimodal programme including physiotherapy and education could improve the symptoms of osteoarthritis of the knee across various severities of disease.

PATIENTS AND METHODS

Seventy-two patients with osteoarthritis of the knee confirmed on radiographic evidence were referred over a 13-month period for a lower limb programme which consisted of 12 classes over 6 weeks of group physiotherapy and included education on osteoarthritis, diet and exercise. Six patients went on to have joint arthroplasty at a mean time of 6.5 months with three placed on the waiting list during follow-up.

RESULTS

Pre-intervention, the mean WOMAC score was 42.0 and the mean Oxford Knee Score was 32.8. Post-intervention at a mean follow-up of 12 months, the mean WOMAC score was 31.6 and the mean Oxford Knee Score 24.3. The change in scores following intervention was statistically significant (P < 0.01). Using the WOMAC scoring system, the greatest effect size was seen in patients with Kellgren-Lawrence grade IV whilst using the Oxford knee scoring system, the greatest effect size was seen in patients with Kellgren-Lawrence grade II.

CONCLUSIONS

At 12 months, a multimodal programme of non-operative interventions has an excellent impact upon the symptoms of osteoarthritis of the knee with improved patient-reported scores. The level of improvement cannot be inferred from the radiographic grade of osteoarthritis. This modality could be considered for all patients with mild-to-moderate osteoarthritis of the knee.

Distinguishing four components underlying physical activity: a new approach to using physical activity questionnaire data in old age

Background

It is evident that physical activity has many benefits, but it often remains unclear which types of activity are optimal for health and functioning in old age. The aim of this methodological study was to propose a method for distinguishing four components underlying self reported physical activity of older adults: intensity, muscle strength, turning actions and mechanical strain.

Methods

Physical activity was assessed by the validated LAPAQ questionnaire among 1699 older adults of the Longitudinal Aging Study Amsterdam. Based on expert consultation and literature review, the four component scores for several individual daily and sports activities were developed. Factor analysis was performed to confirm whether the developed components indeed measured different constructs of physical activity.

Results

Based on the factor analyses, three components were distinguished: 1. intensity and muscle strength loaded on the same factor, 2. mechanical strain and 3. turning actions. Analyses in gender, age and activity level subgroups consistently distinguished three factors.

Conclusion

Future research using these components may contribute to our understanding of how specific daily and sports activities may have a different influence on health and physical functioning in old age.

Sagittal plane knee joint moments following anterior cruciate ligament injury and reconstruction: a systematic review

BACKGROUND

Gait adaptations in persons with anterior cruciate ligament (ACL) injuries have been debated. Many studies examine high speed, 3-dimensional video gait analysis to compare knee joint torques during simulated activities of daily living.

METHODS

We performed a systematic review of the literature for published clinical papers that reported sagittal plane knee joint kinetics in ACL deficient or reconstructed individuals. We calculated weighted effect sizes (Cohen's d) to evaluate the magnitude of differences between the injured limb and the contralateral limb and healthy, uninjured limbs in control subjects.

FINDINGS

Ten published papers reported kinetic data in ACL deficient subjects while walking for comparisons to the contralateral side (weighted average d=-0.83, range: -3.21, 1.07), and to healthy control knees (weighted average d=-1.0, range: -3.36, 0.17); four papers reported data during jogging compared to the contralateral side (weighted average d=-0.94, range: -4.15, 0.17), and to controls (weighted average d=-1.42, range: -3.83,-0.2). Four papers reported data for ACL-reconstructed patients compared to healthy controls during walking (weighted average d=-0.94, range: -0.4, -1.77) and jogging (weighted average d=-1.18).

INTERPRETATION

Effect sizes comparing knee joint moments in injured vs. healthy control subjects appear to be slightly higher while jogging than walking, and higher in ACL-deficient patients compared to reconstructions. However, magnitudes are all large. Few studies report stair climbing. Consequently, it is difficult to make inferences with confidence during these tasks.

Lack of quadriceps dysfunction in women with early knee osteoarthritis

Quadriceps dysfunction, specifically weakness and central activation failure (CAF), has been implicated in the development and progression of knee osteoarthritis (OA), though few data are available to confirm its presence in early OA. The purpose of this study was to determine the presence and magnitude of quadriceps dysfunction in those with and without early knee OA. Thirty-five female volunteers were classified into two groups, OA (n=22) and control (n=13), based on the presence [Kellgren-Lawrence (K-L) grade 2] or absence (K-L grade 0-1) of mild OA, respectively. Isometric quadriceps strength and central activation ratio (CAR) were assessed and compared between groups utilizing a one-way ANOVA. Frequency statistics and Fisher's exact test were used to compare the percentage of women with and without CAF between groups. Quadriceps strength (control: 1.47+/-0.62 Nm/kg; OA: 1.30+/-0.62 Nm/kg; p=0.45) was not significantly different for women with and without mild OA. Further, the CAR (control: 0.91+/-0.07; OA: 0.87+/-0.12; p=0.19) did not differ between groups; however, women in both groups presented with CAF (control: 54%; OA: 73%; p=0.29). Our results suggest that the women with mild osteoarthritis do not present with quadriceps dysfunction.

Beta2-adrenergic agonist-induced hypertrophy of the quadriceps skeletal muscle does not modulate disease severity in the rodent meniscectomy model of osteoarthritis

OBJECTIVE

To examine whether beta2-adrenergic agonist-induced hypertrophy of the quadriceps skeletal muscle can modulate the severity of osteoarthritis (OA) in the rodent meniscectomy (MNX) model.

METHODS

Male Lewis rats were subcutaneously administered with 1.5 mg/kg/day clenbuterol hydrochloride (n=15) or saline vehicle (n=20) for 14 days. Following pre-treatment, five animals from each group were sacrificed to assess the immediate effects of clenbuterol. The remaining animals underwent either invasive knee surgery (clenbuterol pre-treated n=10; saline pre-treated n=10) or a sham control surgical procedure (saline pre-treated n=5). During disease initiation and progression, weight bearing was assessed by hindlimb loading. Myosin heavy chain (MHC) protein isoforms were quantified by silver stained SDS PAGE. OA severity was graded by assessment of toluidine blue stained step coronal sections of the total knee joint.

RESULTS

Clenbuterol treatment resulted in an increase in total bodyweight, growth rate and in quadriceps skeletal muscle mass. Meniscal surgery resulted in the development of OA-like lesions, changes to weight bearing, and changes in MHC protein expression in the quadriceps. Clenbuterol-induced skeletal muscle hypertrophy had no effect on either weight bearing or articular pathology following MNX surgery.

CONCLUSIONS

Our data reveal that clenbuterol-induced skeletal muscle hypertrophy is unable to mimic the beneficial clinical effects of increased musculature derived through targeted strength training in humans, in a rodent model of MNX-induced OA. In addition we observed fibre-type switching to "slow twitch" in the quadriceps muscle during the induction of OA that warrants further investigation as to its relationship to joint stability.

Metabolic activity of osteoarthritic knees correlates with BMI

Osteoarthritis of the knee has consistently been linked to obesity, defined as a body mass index (BMI) >30kg/m(2). It has been hypothesized that obesity may lead to osteoarthritis through increased joint pressure, accumulated microtrauma, and disruption of normal chondrocyte metabolism. These changes in chondrocyte metabolism have not been thoroughly investigated, and it is the purpose of this study to identify a relationship between BMI and altered chondrocyte metabolism in osteoarthritic tissue. Articular cartilage was harvested from the femoral condyles of patients after total knee arthroplasty, and analyzed in explant and alginate models. Glycosaminoglycan (GAG) content was measured using a dimethylmethylene blue assay and normalized to DNA content using a PicoGreen(R) assay. Studies have reported GAGs to be a reliable measurement of chondrocyte metabolism and osteoarthritis progression. Our results show a significant linear relationship of increasing BMI and increasing GAG content in both alginate and explant models (p<0.001 and p=0.001). Obese (BMI>/=30kg/m(2)) and non-obese (BMI<30kg/m(2)) comparisons also demonstrated significant differences with higher GAG/DNA content in obese individuals compared to non-obese (p=0.001 and p=0.015). The study results reveal significant relationships between GAG content and BMI in this population of osteoarthritic patients. The significant difference in GAG content between the obese and non-obese patients supports the connection between osteoarthritis and obesity previously reported. Higher patient BMI (>30kg/m(2)) may be similar to dynamic compression injuries which cause increased GAG synthesis in response to cartilage damage.

Error associated with antagonist muscle activity in isometric knee strength testing

The purpose of this study was to determine the measurement error associated with antagonist muscle activity in isometric knee strength testing at 60 degrees of knee flexion in both sexes. Muscle specific EMG-contraction intensity relationships were obtained from 22 young people by having them match moment targets ranging from 10% to 100% peak moment. The moments attributed to each of the quadriceps and hamstrings muscles were partitioned using a practical mathematical model. Subject specific EMG-moment relationships were defined for each muscle using second-order polynomial equations. These equations were subsequently used to predict the countermoment associated with antagonist muscle activity. Error during strength testing was calculated by expressing net antagonist moments as a percentage of net agonist moments. The net antagonist moments associated with quadriceps and hamstrings muscle activity were 11.0% and 8.7% of the peak moment values recorded when the same muscle groups were acting as agonists. The error associated with antagonist activity was significantly higher in knee flexion (20.1%) than in knee extension (4.5%). Females displayed significantly higher error in knee flexor testing (P < 0.001). Limb symmetry indices did not change significantly when the countermoments generated by the antagonist muscles were accounted for (P > 0.05). The results of this study indicate that the error associated with antagonist activity in knee extensor testing is relatively small, whereas the error in knee flexor testing is larger. This is due to the quadriceps being much stronger than the hamstrings muscles while displaying similar levels of antagonist activity.

Risk stratification for knee osteoarthritis progression: a narrative review

OBJECTIVE

A narrative review describing the assessment of osteoarthritis (OA) progression, and more specifically the risk factors which assist in delineating strata of individuals at greatest risk for more rapid progression.

DESIGN

A narrative review based on selected recent medical literature.

RESULTS

With little currently available in the treatment of this disease, better understanding of responsive and valid endpoints is essential to identifying potential new interventions for treatment of OA. Efforts to stratify those at greatest risk for progression can use a number of systemic or local risk factors that may assist in delineating populations at greater risk for progression.

CONCLUSIONS

Current data suggests that stratification of risk is feasible to ascertain those at risk for rapid progression using a number of different metrics including knee alignment, meniscal damage, bone marrow lesions and late stage disease. Identifying persons at greatest risk for progression has important implications for clinical trial planning and can enhance study efficiency.

Knee extension and flexion weakness in people with knee osteoarthritis: is antagonist cocontraction a factor?

STUDY DESIGN

Controlled laboratory study, cross-sectional data.

OBJECTIVES

To investigate isometric knee flexion and extension strength, failure of voluntary muscle activation, and antagonist cocontraction of subjects with knee osteoarthritis (OA) compared with age-matched asymptomatic control subjects.

BACKGROUND

Quadriceps weakness is a common impairment in individuals with knee OA. Disuse atrophy, failure of voluntary muscle activation, and antagonist muscle cocontraction are thought to be possible mechanisms underlying this weakness; but antagonist cocontraction has not been examined during testing requiring maximum voluntary isometric contraction.

METHODS

Fifty-four subjects with knee OA (mean +/- SD age, 65.6 +/- 7.6 years) and 27 similarly aged control subjects (age, 64.2 +/- 5.1 years) were recruited for this study. Isometric knee flexion and extension strength were measured, and electromyographic data were recorded, from 7 muscles crossing the knee and used to calculate cocontraction ratios during maximal effort knee flexion and extension trials. The burst superimposition technique was used to measure failure of voluntary activation.

RESULTS

Knee extension strength of subjects with knee OA (mean +/- SD, 115.9 +/- 6.7 Nm) was significantly lower than for those in the control group (152.3 +/- 9.6 Nm). No significant between-group difference was found for failure of voluntary muscle activation, or the cocontraction ratios during maximum effort knee flexion or extension.

CONCLUSION

These results demonstrate that the reduction in isometric extension strength, measured with a 90 degrees knee flexion angle, in subjects with knee OA is not associated with increased antagonist cocontraction.

Effect of thigh strength on incident radiographic and symptomatic knee osteoarthritis in a longitudinal cohort

OBJECTIVE

To assess whether knee extensor strength or hamstring:quadriceps (H:Q) ratio predicts risk for incident radiographic tibiofemoral and incident symptomatic whole knee osteoarthritis (OA) in adults ages 50-79 years.

METHODS

We followed 1,617 participants (2,519 knees) who, at the baseline visit of the Multicenter Osteoarthritis (MOST) Study, did not have radiographic tibiofemoral OA and 2,078 participants (3,392 knees) who did not have symptomatic whole knee OA (i.e., did not have the combination of radiographic OA and frequent knee symptoms). Isokinetic strength was measured at baseline, and participants were followed for development of incident radiographic tibiofemoral OA, or incident symptomatic whole knee OA at 30 months. Generalized estimating equations accounted for 2 knees per subject, and multivariable models adjusted for age, body mass index (BMI), hip bone mineral density, knee surgery or pain, and physical activity score.

RESULTS

In the studies of incident radiographic and incident symptomatic knee OA, mean +/- SD ages were 62.4 +/- 8.0 years and 62.3 +/- 8.0 years, respectively, and mean +/- SD BMI scores were 30.6 +/- 5.8 kg/m(2) and 30.2 +/- 5.5 kg/m(2), respectively. Knee extensor strength and H:Q ratio at baseline significantly differed between men and women. Neither knee extensor strength nor the H:Q ratio was predictive of incident radiographic tibiofemoral OA. Compared with the lowest tertile, the highest tertile of knee extensor strength protected against development of incident symptomatic whole knee OA in both sexes (adjusted odds ratio 0.5-0.6). H:Q ratio was not predictive of incident symptomatic whole knee OA in either sex.

CONCLUSION

Thigh muscle strength does not appear to predict incident radiographic OA, but does seem to predict incident symptomatic knee OA.

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.

The effects of impaired joint position sense on the development and progression of pain and structural damage in knee osteoarthritis

OBJECTIVE

Although cross-sectional studies have reported impaired proprioceptive acuity in people with osteoarthritis (OA), there have been no longitudinal studies to evaluate whether those with such impairments increase the risk of OA or its worsening.

METHODS

We studied subjects from the Multicenter Osteoarthritis Study study, a longitudinal study of people with or at high risk of knee OA. At baseline, we quantified acuity as the amount of a subject's error when attempting to reproduce a test knee flexion angle (a measure of joint position sense). We tested proprioception 10 times in the right leg and used a person's worst score as their proprioceptive acuity. At baseline and the 30-month followup, we assessed the presence of frequent pain, obtained Western Ontario and McMasters Universities OA Index (WOMAC) scores, and acquired posteroanterior and lateral weight-bearing knee radiographs read for Kellgren/Lawrence grade and individual radiographic features. We examined the relation of baseline proprioceptive acuity in quartiles with baseline knee pain (frequent pain yes/no), WOMAC pain score, self-reported physical function, and radiographic OA, and with changes from baseline in pain, physical function, and radiographic OA adjusted for age, sex, body mass index, and quadriceps strength.

RESULTS

At baseline, proprioceptive acuity was associated with the presence and severity of knee pain but not with the presence of radiographic OA. However, among the 2,243 subjects with baseline acuity assessments and 30-month followup, there were no strong associations between proprioceptive acuity and development of adverse OA outcomes. Acuity was not significantly associated with the new onset of frequent knee pain. Those with the worst acuity at baseline had slightly greater worsening of WOMAC pain scores (0.47 on a 20-point scale) and physical function scores (by 1.5 points on a 0-68-point scale) compared with those with the best proprioceptive acuity, whose pain and physical function score deteriorated less (for pain P = 0.05; for physical function P = 0.02). Radiographic worsening was not significantly associated with proprioceptive acuity.

CONCLUSION

Proprioceptive acuity as assessed by the accuracy of reproduction of the angle of knee flexion had modest effects on the trajectory of pain and physical functional limitation in knee OA.

Muscle weakness causes joint degeneration in rabbits

OBJECTIVE

The objective of this study was to investigate the effects of botulinum toxin type-A (BTX-A) induced quadriceps weakness on micro-structural changes in knee cartilage of New Zealand White (NZW) rabbits.

DESIGN

Fifteen rabbits were divided randomly into an experimental and a sham control group. Each group received a unilateral single quadriceps muscle injection either with saline (sham control; n=4) or BTX-A (experimental; n=11).

RESULTS

BTX-A injection produced significant quadriceps muscle weakness (P<0.05) and loss of quadriceps muscle mass (P<0.05). Degenerative changes of the knee cartilage, assessed with the Mankin grading system, were the same for the injected and non-injected hind limbs of the experimental group animals. Sham injection had no effect on joint degeneration but all control animals showed some degenerative changes in the knee. Degenerative changes of the retro-patellar cartilage were more severe in the experimental compared to sham control group rabbits (P<0.05). The distal region of the retro-patellar cartilage was more degenerated than the proximal part in the experimental and control group rabbits (P<0.05). The Mankin grades for the tibiofemoral region were not significantly different between experimental and control group rabbits (P>0.05).

CONCLUSION

Quadriceps muscle weakness caused increased degeneration in the retro-patellar cartilage of NZW rabbits, providing evidence that muscle weakness might be a risk factor for the onset and progression of osteoarthritis (OA). Future work needs to delineate whether muscle weakness directly affects joint degeneration, or if changes in function and movement execution associated with muscle weakness are responsible for the increased rate of OA onset and progression observed here.

Insights from imaging on the epidemiology and pathophysiology of osteoarthritis

This article highlights recent studies, particularly those with an emphasis on MR imaging, that are providing unique insights into the relation between structures identified on imaging and symptoms and disease genesis. It is becoming increasingly apparent that the subchondral bone, periosteum, periarticular ligaments, periarticular muscle spasm, synovium, and joint capsule are all richly innervated and are the likely source of nociception in osteoarthritis. It is also apparent that local tissue alterations in the bone and meniscus and alignment of the lower extremity are important in terms of disease genesis. This article represents the literature in that much of the focus and understanding is knee centric with less focus on the hip and hand.

Primary osteoarthritis no longer primary: three subsets with distinct etiological, clinical, and therapeutic characteristics

BACKGROUND

Osteoarthritis (OA) has been historically divided into primary and secondary. Primary OA has been defined as an idiopathic condition developing in previously undamaged joints in the absence of an obvious causative mechanism. During the last few years a large amount of evidence has provided new insights into the biochemistry and molecular biology of cartilage, subchondral bone, and other articular tissues, which suggest distinct etiopathogenetic mechanisms in some forms of primary OA.

OBJECTIVE

To propose an etiopathogenic classification of primary OA in the light of the significant progress in the understanding of the disease.

METHODS

A review of the literature was performed by searching the Medline and PubMed databases from 1952 to November 2008 using the following keywords: genetic alteration, heritability, estrogen, menopause, and aging either alone or in various combinations with joint, cartilage, subchondral bone, synovium, ligaments, muscle, tendons, OA, and osteoporosis.

RESULTS

Numerous studies have shown that genetic alterations, menopause-related estrogen deficiency, and aging play crucial roles in the molecular pathophysiological events involved in the process of cartilage and joint damage and thus in development of OA. We propose classifying primary OA into 3 distinct although interrelated subsets: type I OA, genetically determined; type II OA, estrogen hormone dependent; and type III OA, aging related.

CONCLUSIONS

The 3 proposed subsets of OA display distinct etiological, clinical, and therapeutic characteristics and should therefore no longer be considered to be "Primary OA."

Exercise and osteoarthritis

Exercise remains an extremely popular leisure time activity in many countries throughout the western world. It is widely promoted in the lay press as having salutory benefits for weight control, disease management advantages for cardiovascular disease and diabetes, in addition to improving psychological well-being amongst an array of other benefits. In contrast, however, the lay press and community perception is also that exercise is potentially deleterious to one's joints. The purpose of this review is to consider what osteoarthritis (OA) is and provide an overview of the epidemiology of OA focusing on validated risk factors for its development. In particular the role of both exercise and occupational activity in OA will be described as well as the role of exercise to the joints' tissues (particularly cartilage) and the role of exercise in disease management. Despite the common misconception that exercise is deleterious to one's joints, in the absence of joint injury there is no evidence to support this notion. Rather it would appear that exercise has positive salutory benefits for joint tissues in addition to its other health benefits.

Perturbation training prior to ACL reconstruction improves gait asymmetries in non-copers

We investigated whether preoperative perturbation training would help anterior cruciate ligament (ACL) deficient individuals who complain of knee instability ("non-copers") regain quadriceps strength and walk normally after ACL reconstruction. Nineteen non-copers with acute ACL injury were randomly assigned into a perturbation group (PERT) or a strengthening group (STR). The PERT group received specialized neuromuscular training and progressive quadriceps strength training, whereas the STR group received progressive quadriceps strength training only. We compared quadriceps strength indexes and knee excursions during the mid-stance phase of gait preoperatively to data collected 6 months after ACL reconstruction. Analyses of Variance with repeated measures (time/limb) were conducted to compare quadriceps strength index values over time (time x group) and differences in knee excursions in limbs between groups over time (limb x time x group). If significance was found, post hoc analyses were performed using paired and independent t-tests. Quadriceps strength indexes before intervention (Pert: 87.2%; Str: 75.8%) improved 6 months after ACL reconstruction in both groups (Pert: 97.1%; Str: 94.4%). Non-copers who received perturbation training preoperatively had no differences in knee excursions between their limbs 6 months after ACL reconstruction (p = 0.14), whereas those who received just strength training continued to have smaller knee excursions during the mid-stance phase of gait (p = 0.007). Non-copers strength and knee excursions were more symmetrical 6 months postoperatively in the group that received perturbation training and progressive quadriceps strength training than the group who received strength training alone.

Relationship between cartilage glycosaminoglycan content (assessed with dGEMRIC) and OA risk factors in meniscectomized patients

OBJECTIVE

To study the relationship between cartilage integrity, assessed with [delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC)] and epidemiologic risk factors for knee osteoarthritis (OA) in meniscectomized patients.

METHODS

Body mass index (BMI) was calculated in 45 patients (16 women), mean age 46, who underwent an arthroscopic medial meniscectomy 1-6 years earlier. The cartilage glycosaminoglycan (GAG) content was estimated by dGEMRIC Index and tests of isokinetic muscle strength and functional performance (one-leg hop test) were conducted.

RESULTS

BMI ranged from 20.0 to 34.3 (mean: 26.5). The dGEMRIC Index was 14.4% lower in the medial index compartment (374+/-61 ms, mean+/-SD) than in the lateral reference compartment (437+/-59 ms, mean+/-SD) (P<0.001). The dGEMRIC Index of the medial diseased compartment correlated positively with both knee flexor (r=0.50, P=0.001) and knee extensor strength (r=0.47, P=0.001) relative to body weight and with the one-leg hop test (r=0.42, P=0.004). Furthermore, a negative correlation was found between the dGEMRIC Index of the medial compartment and BMI (r=-0.35, P=0.019). No significant correlations were found in the lateral reference compartment.

CONCLUSION

The lower dGEMRIC Index of the medial compartment suggests decreased cartilage GAG content after medial meniscectomy, indicating an early stage OA. Furthermore, results suggest that overweight is a factor that deteriorates cartilage, whereas strong and co-ordinated thigh muscles may have a protective effect on the cartilage integrity.

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.

Multiple ligament knee reconstruction clinical follow-up and gait analysis

Multiple ligament knee injuries are serious and rare injures that have not been studied using advanced gait analysis techniques. The purpose of this study was to perform clinical follow-up and gait analysis on patients with multiple knee ligament reconstruction. Twenty-four patients who underwent a multi-ligament knee reconstruction by a single surgeon volunteered to participate in this study. We performed complete clinical exam including instrumented ACL exam (KT-1000), and radiological exam including weight-bearing and PCL stress radiographs (TELOS) at minimum 2 years post index surgery. In addition, we performed complete three-dimensional gait analysis on 18 patients. We used a 10-camera, high speed (120 Hz) motion analysis system in conjunction with a multi-axis strain-gage force plate which calculated knee joint kinetics and kinematics while subjects performed flat-ground walking and stair-descent tasks. Kinematic and kinetic variables were compared between reconstructed and contralateral knees and unmatched, healthy control knees. All knee joint moments were normalized to subjects' weight. Clinical: Average knee joint flexion/extension 123.6 +/- 15.5/1.7 +/- 3.5, respectively. Average KT-1000 side-to-side difference was 1.2 +/- 2.0 mm, TELOS side-to-side difference on stress radiographs was 4.0 +/- 3.1 mm. Median IKDC score was 67 (range 13-94). Fifty-three percent of patients exhibited radiographic evidence of osteoarthritis (OA) on the operative side; one patient on the contralateral knee. During gait analysis, patients exhibited significantly reduced total knee joint range of motion, and external knee flexion moment in the reconstructed knee compared to the contralateral knee and healthy control knees. The magnitude of these differences was greater while descending a step. Finally, patients who had radiographic evidence of knee joint OA had significantly lower magnitude external knee flexion moment compared to those who did not have OA at the time of follow-up. Greater than 2 years after reconstruction, patients with multi-ligament knee injuries are able to return to daily activities. Gait analysis data suggests that patients may be experiencing higher magnitude changes in sagittal plane kinematics and kinetics during demanding functional tasks (stair decent). Changes in walking gait biomechanics may help explain why this group is experiencing unilateral knee joint degeneration.

Focusing osteoarthritis management on modifiable risk factors and future therapeutic prospects

The pathogenesis of osteoarthritis (OA) appears to be the result of a complex interplay between mechanical, cellular, and biochemical forces. Obesity is the strongest risk factor for disease onset and mechanical factors dominate the risk for disease progression. This narrative review focuses on the influence of biomechanics and obesity on the etiology of OA and its symptomatic presentation. We need to revisit the way we currently manage the disease and focus on the modifiable, primarily through nonpharmacologic intervention. Greater therapeutic attention to the important role of mechanical factors and obesity in OA etiopathogenesis is required if we are to find ways of reducing the public health impact of this condition.

Etiopathogenesis of osteoarthritis

Because of the implications for prevention and treatment, how a clinician views osteoarthritis (OA) matters. We view OA as an attempt to contain a mechanical problem in the joint and as failed repair of damage caused by excessive mechanical stress on the joint. OA is organ failure of the synovial joint. Because of insufficient focus on reduction of the habitually loaded contact area of the joint and on aberrant loading, we believe that therapeutic efforts aimed at pathogenetic mechanisms in OA have been misdirected: neither the large role that a reduction of excessive levels of mechanical stress plays in promoting the healing response in OA nor the evidence that relief of joint pain and improvement in function, rather than the appearance of the articular surface, are the most important outcomes of the healing process have been sufficiently emphasized. Various mechanical abnormalities can trigger the processes involved in repair and attempts by the joint to contain the mechanical insult, but without a return to mechanical normality, attempts at healing will fail. In our view, drugs may be helpful symptomatically, but cannot accomplish this. In our view, as long as the joint remains in the same adverse mechanical environment that got it into trouble in the first place, it is unlikely that a drug that inhibits a specific enzyme or cytokine in the pathways of cartilage breakdown, or further stimulates the already increased synthesis of cartilage matrix molecules will solve the problem of OA. Also, because the subchondral bone is critically important in containing the mechanical abnormalities that damage the cartilage, emphasis on cartilage repair alone is likely to be futile. On the other hand, if the abnormal stresses on the joint are corrected, intervention with a structure-modifying drug may be superfluous.

THE EFFECT OF PHYSICAL TRAINING ON THE LOCOMOTOR APPARATUS IN ELDERLY PEOPLE

Physiological changes taking place on the locomotive apparatus as a result of aging, such as muscular mass loss, body balance loss, reduced bone mass and osteoarthrosis cause limitations to the daily activities of elderly people, compromising their quality of life and making them weaker and dependent. Aged people who regularly practice physical activities have a higher level of functional independence and a better quality of life than the sedentary ones. This article addresses the key physiological changes with aging and provides a review of current literature about the effects of physical exercises on the locomotive apparatus of elderly individuals, specifying the best ways to prescribe physical exercises to this age group.

Physical function and properties of quadriceps femoris muscle in men with knee osteoarthritis

OBJECTIVES

To examine the objective physical function of the lower extremities, to measure the properties of quadriceps femoris muscle (QFM), and to assess subjective disabilities in men with knee osteoarthritis (OA) and to compare the results with those obtained from age- and sex-matched control subjects.

DESIGN

Cross-sectional study.

SETTING

Rehabilitation clinic in a university hospital.

PARTICIPANTS

Male volunteers (n=54) (age range, 50-69y) with knee OA and randomly selected healthy, age- and sex-matched control subjects (n=53).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Physical function evaluated with a test battery including the QFM composition measurement, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the RAND 36-Item Short-Form Health Survey, version 1.0.

RESULTS

Knee OA patients had 13% to 26% poorer (P range, .050-.001) physical function and muscle strength compared with the controls. There were also significant differences in QFM composition. WOMAC (P range, .050-.001) and muscle strength (P<.001) associated with physical function tests, but subjective pain correlated with neither physical function nor muscle strength in knee OA patients. The radiographic knee OA grade did not have any significant effect on physical function, but passive knee motion, knee extension strength, and WOMAC were related to the severity of the disease (P<.05).

CONCLUSIONS

The patients with knee OA exhibited impaired physical function and muscle strength and QFM composition compared with healthy controls. The severity of radiographic knee OA clearly had adverse effects on functional ability at the later stages of the disease. The results highlight the effect of QFM strength on physical function as well as the importance of patient's subjective and objective physical function when deciding on knee OA treatment policy.

Generalized vibratory deficits in osteoarthritis of the hip

OBJECTIVE

Lower extremity sensory deficits, including reduced proprioception, joint kinesthesia, and, recently, vibratory sense, have been described in subjects with osteoarthritis (OA) of the knee. However, comparable deficits in OA of the hip have not previously been evaluated. Vibratory perception threshold (VPT) is a reliable measure used to assess sensory deficits and is amenable to testing multiple body sites. This study examined VPT at the upper and lower extremities of subjects with hip OA compared with subjects without hip OA.

METHODS

Fourteen subjects with symptomatic and radiographic hip OA were compared with 13 age-matched controls without hip OA. VPT was assessed using a biothesiometer. Five sites in the lower extremity and 1 site in the upper extremity (radial head) were evaluated and compared between OA and control subjects.

RESULTS

VPT was significantly reduced at all 6 testing sites of the OA subjects compared with controls (P < 0.05 for all sites). VPT scores (mean +/- SEM volts) for OA subjects and controls were as follows: first metatarsophalangeal joint (13.5 +/- 1.4 versus 7.4 +/- 0.7), medial malleolus (18.1 +/- 2.6 versus 11.2 +/- 1.7), lateral malleolus (20.9 +/- 2.4 versus 10.6 +/- 1.5), medial femoral condyle (22.8 +/- 2.9 versus 12.6 +/- 1.3), lateral femoral condyle (26.7 +/- 2.6 versus 16.2 +/- 1.9), and radial styloid [corrected] (10.2 +/- 0.8 versus 7.5 +/- 0.6).

CONCLUSION

To our knowledge, this is the first study to evaluate sensory deficits in hip OA and to demonstrate that there is vibratory sense loss at both the upper and lower extremities in these subjects compared with controls. The noted generalized deficits may have significant implications in the neuromechanical pathophysiology of OA.

Mechanisms underlying quadriceps weakness in knee osteoarthritis

PURPOSE

To identify determinants of quadriceps weakness among persons with end-stage knee osteoarthritis (OA).

METHODS

One-hundred twenty-three individuals (mean age 64.9 +/- 8.5 yr) with Kellgren/Lawrence grade IV knee OA participated. Quadriceps strength (MVIC) and volitional muscle activation (CAR) were measured using a burst superimposition test. Muscle composition (lean muscle cross-sectional area (LMCSA) and fat CSA (FCSA)) were quantified using magnetic resonance imaging. Specific strength (MVIC/LMCSA) was computed. Interlimb differences were analyzed using paired-sample t-tests. Regression analysis was applied to identify determinants of MVIC. An alpha level of 0.05 was adopted.

RESULTS

The OA limb was significantly weaker, had lower CAR, and had smaller LMCSA than the contralateral limb. CAR explained 17% of the variance in the contralateral limb's MVIC compared with 40% in the OA limb. LMCSA explained 41% of the variance in the contralateral limb's MVIC compared with 27% in the OA limb.

CONCLUSION

Both reduced CAR and LMCSA contribute to muscle weakness in persons with knee OA. Similar to healthy elders, the best predictor of strength in the contralateral, nondiseased limb was largely determined by LMCSA, whereas CAR was found to be the primary determinant of strength in the OA limb. Deficits in CAR may undermine the effectiveness of volitional strengthening programs in targeting quadriceps weakness in the OA population.

Unilateral thigh atrophy and weakness in hip osteoarthritis

Osteoarthritis is a common condition that affects a significant percentage of people in the United States. The case and discussion will serve to introduce to the neurologist the issue of hip osteoarthritis causing thigh atrophy and weakness. The pathogeneses of muscular atrophy in the setting of osteoarthritis and of muscle weakness as a cause of osteoarthritis will be explored.