The relation of peripheral and central sensitization to muscle co-contraction: the MOST study

OBJECTIVE

To examine the relation of pain sensitization to altered motor activity in knee OA as assessed by hamstrings muscle co-contraction during maximal effort knee extension.

DESIGN

Medial, lateral, and overall hamstring co-contraction was assessed in the Multicenter Osteoarthritis (MOST) Study cohort using electromyography during isokinetic knee extension at 60°/second. Mechanical temporal summation of pain (TS) was assessed at the right wrist and pressure pain thresholds (PPT) were assessed at the patellae; PPTs were categorized into sex-specific tertiles. Muscle co-contraction was categorized into age- and sex-specific tertiles. We evaluated the relation of measures of sensitization to muscle co-contraction using a generalized logistic regression model.

RESULTS

1633 participants were included: mean age and BMI was 67.3 ± 7.7 years and 30.3 ± 5.6 kg/m2, respectively; 58% were female. Presence of TS was associated with higher overall (OR 1.3, 95% confidence interval (CI) (1.0-1.8)), medial (1.4 (1.0-1.9), and lateral (1.3 (1.0, 1.9)) hamstring co-contraction. The lowest PPT tertile (greater sensitivity) was associated with higher overall (1.5 (1.0, 2.3)) and medial (1.5 (1.0, 2.3)) hamstring co-contraction compared with those in the highest PPT tertile.

CONCLUSION

Greater pain sensitization, as assessed by presence of TS at the wrist and low patellar PPT, was associated with greater overall and medial hamstring co-contraction during knee extension. This provides support to the possibility that peripheral and/or central nervous system alterations may not only affect pain sensitivity, but also motor function.

Influence of Antagonistic Hamstring Coactivation on Measurement of Quadriceps Strength in Older Adults

BACKGROUND

There is limited understanding of how antagonist muscle coactivation relates to measurement of strength in both individuals with and without knee osteoarthritis (KOA).

OBJECTIVE

This study sought to determine whether hamstring coactivation during a maximal quadriceps activation task attenuates net quadriceps strength.

DESIGN

Cross-sectional cohort analysis was conducted using data from the 60-month visit of the Multicenter Osteoarthritis Study (MOST).

SETTING

Laboratory.

PARTICIPANTS

A sample of 2328 community-dwelling MOST participants between the ages of 55 and 84 years, with or at elevated risk for KOA, completed the 60-month MOST follow-up visit. Of these, 1666 met inclusion criteria for the current study.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE(S)

Quadriceps strength; percentage of combined hamstring coactivation (HC), medial HC, and lateral HC. Quadriceps and hamstring strength were assessed using an isokinetic dynamometer. Surface electromyography was used to assess muscle activation patterns. General linear models, adjusted for age, BMI, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Kellgren-Lawrence (KL) grade and study site, modeled the relationship between antagonist hamstring coactivation and quadriceps strength.

RESULTS

Men had significantly greater quadriceps strength (P < .001), history of knee injury (P < .001) and surgery (P = .002), and greater presence of varus malalignment (P < .001). Women had greater pain (P < .001) and proportion of KL grade ≥2 (P = .017). Gender-specific analyses revealed combined HC (P = .013) and lateral HC inversely associated with quadriceps strength in women (P = .023) but not in men (combined HC P = .320, lateral HC P = .755). A nonlinear association was detected between quadriceps strength and medial HC. Assessment of quartiles of medial HC revealed the third quartile had reduced quadriceps strength when compared to the lowest quartile of coactivation in both men and women.

CONCLUSIONS

Hamstring coactivation attenuates measured quadriceps strength in women with or at elevated risk for KOA.

LEVEL OF EVIDENCE

II.

The Association of Parity with Greater Dynamic Pronation of the Feet

BACKGROUND

Postpartum women are at increased risk for lower limb musculoskeletal disorders. Foot arch collapse following pregnancy has been reported as a mechanism for this increased risk. However, dynamic changes during gait in postpartum women have not been reported. Therefore, we assessed the association between parity and dynamic foot pronation during gait.

OBJECTIVE

To determine (1) if there is an association between parity and dynamic foot pronation (center of pressure excursion index, CPEI) during gait; and (2) the extent to which there is a dose-effect of parity on foot pronation.

DESIGN

The Multicenter Osteoarthritis Study (MOST) Study is a longitudinal cohort study of adults with or at risk for knee osteoarthritis (OA).

SETTING

Two communities in the United States, Birmingham, Alabama and Iowa City, Iowa.

INTERVENTIONS

Not applicable PARTICIPANTS: A population-based sample of 1177 MOST participants who were female, had complete CPEI and parity data and completed the baseline, 30- and 60-month visits.

MAIN OUTCOME MEASURES

Odds of a one quintile decrease in CPEI by parity group and mean CPEI by parity group.

RESULTS

In 1177 women, mean age was 67.7 years and mean body mass index (BMI) was 30.6 kg/m² . As parity increased, there was significantly greater foot pronation, lower mean CPEI: 19.1 (18.2-20.1), 18.9 (18.4-19.4), 18 (17.5-18.6) to 17.5 (16.4-18.6) in the 0 to 4 and >5 children groups, respectively; (P = .002), which remained significant after adjusting for race and clinic site (P = .005). There was a positive linear trend (β = 1.08, 1.03-1.14) in odds ratios of a one quintile decrease in CPEI (greater pronation) with increasing parity level (P = .004), which remained significant after adjusting for race and clinic site (P = .01). After adjusting for age and BMI, these two associations were no longer statistically significant.

CONCLUSIONS

This study indicates a positive correlation between parity and greater dynamic pronation of the feet.

Step Rate and Worsening of Patellofemoral and Tibiofemoral Joint Osteoarthritis in Women and Men: The Multicenter Osteoarthritis Study

OBJECTIVE

To determine the association of self-selected walking step rate with worsening of cartilage damage in the patellofemoral (PF) joint and tibiofemoral (TF) joint compartments at a 2-year follow-up visit.

METHODS

The Multicenter Osteoarthritis Study (MOST) is a prospective cohort of men and women with or at risk of knee osteoarthritis. Self-selected step rate was measured using an instrumented GAITRite walkway (CIR Systems) at the 60-month visit. Cartilage damage was semiquantitatively graded on magnetic resonance images at the 60- and 84-month visits in the medial and lateral PF and TF compartments. Step rate was divided into quartiles, and logistic regression was used to determine the association of step rate with the risk of worsening cartilage damage in men and women separately. Analyses were adjusted for age, body mass index, and knee injury/surgery.

RESULTS

A total of 1,089 participants were included. Mean ± SD age was 66.9 ± 7.5 years, mean ± SD body mass index was 29.6 ± 4.7 kg/m2 , and 62.3% of the participants were women. Women with the lowest step rate had increased risk of lateral PF (risk ratio [RR] 2.1 [95% confidence interval (95% CI) 1.1-3.8]) and TF (RR 1.8 [95% CI 1.1-2.9]) cartilage damage worsening 2 years later compared to those with the highest step rate. Men with the lowest step rate had increased risk of medial TF cartilage damage worsening 2 years later (RR 2.1 [95% CI 1.1-3.9]).

CONCLUSION

Lower step rate was associated with increased risk of cartilage damage worsening in the lateral PF and TF compartments in women and worsening medial TF joint damage in men. Future research is necessary to understand the influence of step rate manipulation on joint biomechanics in women and men.

Association of Diabetes Mellitus and Biomarkers of Abnormal Glucose Metabolism With Incident Radiographic Knee Osteoarthritis

OBJECTIVE

The association of diabetes mellitus (DM) with increased risk of knee osteoarthritis (OA) is uncertain. We evaluated associations of DM and biomarkers of abnormal glucose metabolism with incident radiographic knee OA, controlling for body mass index (BMI).

METHODS

Participants (mean ± SD age 60.6 ± 7.8 years; mean ± SD body mass index [BMI] 29.1 ± 4.9 kg/m2 ) were from the Multicenter Osteoarthritis Study and did not have radiographic knee OA at baseline (Kellgren/Lawrence [K/L] grade <2 bilaterally). A random sample (n = 987) was selected and stratified by BMI. Baseline serum fasting glucose and homeostasis model assessment-estimated insulin resistance (HOMA-IR) were measured. Participants were categorized as having DM based on self-report, use of medication, or fasting glucose ≥126 mg/dl. Incident radiographic knee OA (K/L grade ≥2 or knee replacement) was assessed at 3 follow-up visits (30, 60, and 84 months). Knee-level pooled logistic regression analysis was performed to obtain odds ratios (ORs) (95% confidence interval [95% CI]) for associations of DM status and biomarkers of abnormal glucose metabolism with incident radiographic knee OA.

RESULTS

After adjustment for BMI, the odds of incident radiographic knee OA were not associated with baseline DM status nor with levels of fasting glucose and HOMA-IR, overall and in men. In women, HOMA-IR was inversely associated with odds of incident radiographic knee OA (adjusted OR 0.80 [95% CI 0.69-0.94], P = 0.005).

CONCLUSION

DM and higher levels of biomarkers of abnormal glucose metabolism were not associated with increased odds of incident radiographic knee OA after adjusting for BMI in this cohort overall. A possible protective association of higher HOMA-IR with incident radiographic knee OA in women warrants further investigation.

The Relationship of Three-Dimensional Joint Space Width on Weight Bearing CT With Pain and Physical Function

Limitations of plain radiographs may contribute to poor sensitivity in the detection of knee osteoarthritis and poor correlation with pain and physical function. 3D joint space width, measured from weight bearing CT images, may yield a more accurate correlation with patients' symptoms. We assessed the cross-sectional association between 3D joint space width and self-reported pain and physical function. 528 knees (57% women) were analyzed from Multicenter Osteoarthritis Study participants. An upright weight bearing CT scanner was used to acquire bilateral, weight-bearing fixed-flexion images of the knees. A 3D dataset was reconstructed from cone beam projections and joint space width was calculated across the joint surface. The percentages of the apposed medial tibiofemoral joint surface with joint space width <2.0mm and <2.5mm respectively were calculated. Pain and physical function were measured using Western Ontario and McMaster Universities Osteoarthritis Index. Participants who reported greater pain severity tended to have a greater joint area with joint space width <2.0mm (p=.07 for the highest vs. the lowest tertile). Participants who reported greater functional limitations had a greater joint area with joint space width <2.0mm (p=.02 for the highest vs. the lowest tertile). There appears to be an association between the medial tibiofemoral area with joint space width <2.0mm and pain and physical function. This article is protected by copyright. All rights reserved.

Sex-Specific Influence of Quadriceps Weakness on Worsening Patellofemoral and Tibiofemoral Cartilage Damage: A Prospective Cohort Study

OBJECTIVE

Reports on quadriceps weakness as a risk factor for incident and progressive knee osteoarthritis are conflicting, potentially due to differing effects of muscle strength on patellofemoral and tibiofemoral compartments. This study aimed to examine the sex-specific relation of quadriceps strength to worsening patellofemoral and tibiofemoral cartilage damage over 84 months.

METHODS

The Multicenter Osteoarthritis Study is a cohort study of individuals with or at risk for knee osteoarthritis. Maximal quadriceps strength was assessed at baseline. Cartilage damage was semiquantitatively assessed by magnetic resonance imaging at baseline and 84-month follow-up using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Worsening patellofemoral and tibiofemoral cartilage damage was defined as any WORMS score increase in each subregion within medial and lateral compartments separately. Logistic regression with generalized estimating equations was used to assess the sex-specific relation of quadriceps strength to worsening cartilage damage.

RESULTS

A total of 1,018 participants (mean ± SD age 61 ± 8 years, and mean ± SD body mass index 29.3 ± 4.5 kg/m2 ; 64% female) were included. Quadriceps weakness increased the risk of worsening lateral patellofemoral cartilage damage in women (risk ratio for lowest versus highest quartile of strength 1.50 [95% confidence interval 1.03-2.20]; P = 0.007 for linear trend) but not in men. There was generally no association between quadriceps weakness and worsening cartilage damage in the medial or lateral tibiofemoral compartment for either women or men.

CONCLUSION

Low quadriceps strength increased the risk of worsening cartilage damage in the lateral patellofemoral joint of women, suggesting that optimizing quadriceps strength may help prevent worsening of structural damage in the patellofemoral joint in women.

Thresholds in the Relationship of Quadriceps Strength With Functional Limitations in Women With Knee Osteoarthritis

OBJECTIVE

To investigate thresholds of strength below which individuals with knee osteoarthritis (OA) may have more difficulty carrying out physical functions of daily life. Individuals below such thresholds might benefit more from strengthening interventions than those with greater strength.

METHODS

We studied individuals with symptomatic OA at baseline in the Multicenter Osteoarthritis Study who had knee extensor strength measured isokinetically at 60º/second. Participants underwent a 20-meter walk test and a sit-to-stand test and answered questions from the Western Ontario and McMaster Universities Osteoarthritis Index. Physical function results were plotted against measures of quadriceps strength (Nm) (and as strength:body weight) for the worst knee. Loess technique was used to examine inflection points. Nonlinear relationships were examined in piecewise linear regression models. Differences were tested using linear and logistic regression models.

RESULTS

The study had 834 participants (65.8% women). The mean ± SD age of the participants was 62.9 ± 7.9 years. In women, there were thresholds of strength below which the slope of strength versus function was steeper: walking speed (<58 Nm), chair stand time (<32 Nm), and the McMaster Universities Osteoarthritis Index functions of rising from a chair and getting on/off the toilet (<38 Nm). We found no thresholds in men. Loess analyses using strength:weight showed similar results.

CONCLUSION

In individuals with symptomatic knee OA, thresholds in the strength function relationship may help identify individuals, especially women, at the brink of disability insofar as strength and capacity for daily tasks. In those with low strength, small increments in strength may be associated with improvement in function and greater ease with common daily life, emphasizing the importance of preventing loss of strength.

Concurrent Change in Quadriceps Strength and Physical Function Over Five Years in the Multicenter Osteoarthritis Study

OBJECTIVE

Quadriceps weakness, associated with functional limitations, is a target of treatment of knee osteoarthritis (OA). Limited data exist on the relationship between modest strength increases and improvements in function. The aim of this study was to evaluate concurrent change in strength and physical function over 5 years.

METHODS

Among subjects from the Multicenter Osteoarthritis (MOST) study, we excluded those with knee replacement after baseline. A 3-category variable defined whether, at 5 years, knee extensor strength increased, decreased, or remained within 15% of baseline, a clinically important cut-off. The outcomes were the 5-times sit-to-stand test, 20-meter walk test, Western Ontario and McMaster Universities Osteoarthritis (WOMAC) physical function score, and 3 individual physical functions from WOMAC: arising from a chair, going up stairs, and getting on/off toilet. Linear and logistic models, stratified by sex, evaluated associations between change in strength and change in physical function over 5 years. To compare weaker versus stronger women, we stratified analyses at 56 Nm baseline strength.

RESULTS

Among 1,534 participants (60.6% women), 22% of men and 30% of women increased strength by at least 15% at 5 years. Compared with women whose strength did not change, women whose strength increased had improved chair stand performance (odds ratio 2.27 [95% confidence interval 1.56, 3.30]) but no improvement in other functions. In men, an increase in strength was not associated with significant improvement in physical function. Similar results were observed for a 20% or 30% increase.

CONCLUSION

Modest improvement in quadriceps strength was associated with improved chair stand performance in women but not in men. Most functions did not improve with an increase in strength, and targeted interventions may be required to improve functional status.

Pain Susceptibility Phenotypes in Those Free of Knee Pain With or at Risk of Knee Osteoarthritis: The Multicenter Osteoarthritis Study

OBJECTIVE

It is not clear why some individuals develop pain with knee osteoarthritis (OA). We undertook this study to identify pain susceptibility phenotypes (PSPs) and their relationship to incident persistent knee pain (PKP) 2 years later.

METHODS

We identified individuals free of PKP from the Multicenter Osteoarthritis Study, a longitudinal cohort of older adults with or at risk of knee OA. Latent class analysis was used to determine PSPs that may contribute to development of PKP apart from structural pathology. These included widespread pain, poor sleep, and psychological factors as well as pressure pain threshold and temporal summation (TS) as determined by quantitative sensory testing (QST). We used logistic regression to evaluate the association of sociodemographic factors with PSPs and the relationship of PSPs to the development of PKP over 2 years.

RESULTS

A total of 852 participants were included (mean age 67 years, body mass index 29.5 kg/m² , 55% women). Four PSPs were identified, primarily characterized by varying proportions (low/absent, moderate, or high) of the presence of pressure pain sensitivity and of facilitated TS, reflecting different measures of sensitization. Subjects in the PSP with a high proportion of pressure pain sensitivity and a moderate proportion of facilitated TS were twice as likely to develop incident PKP over 2 years (odds ratio 1.98 [95% confidence interval 1.07-3.68]) compared with subjects in the PSP having a low proportion of sensitization by both measures.

CONCLUSION

Four PSPs were identified, 3 of which were predominated by QST evidence of sensitization and 1 of which was associated with developing PKP 2 years later. Prevention or amelioration of sensitization may be a novel approach to preventing onset of PKP in OA.

Predicting meniscal tear stability across knee-joint flexion using finite-element analysis

PURPOSE

To analyse the stress distribution through longitudinal and radial meniscal tears in three tear locations in weight-bearing conditions and use it to ascertain the impact of tear location and type on the potential for healing of meniscal tears.

METHODS

Subject-specific finite-element models of a healthy knee under static loading at 0°, 20°, and 30° knee flexion were developed from unloaded magnetic resonance images and weight-bearing, contrast-enhanced computed tomography images. Simulations were then run after introducing tears into the anterior, posterior, and midsections of the menisci.

RESULTS

Absolute differences between the displacements of anterior and posterior segments modelled in the intact state and those quantified from in vivo weight-bearing images were less than 0.5 mm. There were tear-location-dependent differences between hoop stress distributions along the inner and outer surfaces of longitudinal tears; the longitudinal tear surfaces were compressed together to the greatest degree in the lateral meniscus and were most consistently in compression on the midsections of both menisci. Radial tears resulted in an increase in stress at the tear apex and in a consistent small compression of the tear surfaces throughout the flexion range when in the posterior segment of the lateral meniscus.

CONCLUSIONS

Both the type of meniscal tear and its location within the meniscus influenced the stresses on the tear surfaces under weight bearing. Results agree with clinical observations and suggest reasons for the inverse correlation between longitudinal tear length and healing, the inferior healing ability of medial compared with lateral menisci, and the superior healing ability of radial tears in the posterior segment of the lateral meniscus compared with other radial tears. This study has shown that meniscal tear location in addition to type likely plays a crucial role in dictating the success of non-operative treatment of the menisci. This may be used in decision making regarding conservative or surgical management.

Brief Report: Leg Length Inequality and Hip Osteoarthritis in the Multicenter Osteoarthritis Study and the Osteoarthritis Initiative

OBJECTIVE

Studies suggest that persons with a leg length inequality (LLI) of ≥2 cm have an increased risk of developing knee osteoarthritis (OA) in that limb. The present study was undertaken to examine whether LLI also confers an increased risk of hip OA.

METHODS

Using long limb radiographs from subjects in the Multicenter Arthritis Study (MOST) and the Osteoarthritis Initiative (OAI), we measured LLI and scored hip radiographs that were obtained at baseline and 3-5-year follow-up. The associations of LLI of ≥1 cm and LLI of ≥2 cm with radiographic hip OA were examined cross-sectionally and longitudinally, assessing risk in shorter limbs and longer limbs compared to limbs from subjects with no LLI. We carried out logistic regression analyses with generalized estimating equations and adjusted for age, sex, body mass index, height, and cohort of origin.

RESULTS

There were 1,966 subjects from the MOST and 2,627 subjects from the OAI. Twelve percent had LLI of ≥1 cm and 1% had LLI of ≥2 cm. For LLI ≥1 cm, the adjusted odds ratio for prevalent hip OA in the shorter leg was 1.47 (95% confidence interval [95% CI] 1.07-2.02) and for LLI ≥2 cm, it was 2.15 (95% CI 0.87-5.34). For LLI ≥1 cm, the odds of incident hip OA in the shorter leg were 1.39 (95% CI 0.81-2.39) while for LLI ≥2 cm, they were 4.20 (95% CI 1.26-14.03). We found no increased risk of hip OA in longer limbs.

CONCLUSION

Our findings suggest that, as with knee OA, legs that are at least 2 cm shorter than the contralateral leg are at increased risk of hip OA.

Is muscle strength in a painful limb affected by knee pain status of the contralateral limb? - Data from the Osteoarthritis Initiative

Contralateral knee pain has been suggested to be associated with muscle weakness in a pain-free knee, potentially through a mechanism of central nervous inhibition. Whether contralateral knee pain also affects muscle strength in a painful knee, however, is unknown. Here we study the extent to which isometric muscle strength differs between matched painful limbs of people with unilateral knee pain vs. matched painful limbs people with bilateral knee pain. To that end, 163 participants with unilateral knee pain were identified from the Osteoarthritis Initiative. Unilaterally painful (UP) limbs were defined as having numerical rating scale (NRS) ≥4/10, infrequent/frequent pain in the painful limb, while contralateral pain-free limbs were defined by NRS=0-1, no/infrequent pain and Western Ontario and McMaster Universities Arthritis Index (WOMAC) ≤1. The comparator group were matched bilaterally painful (BP) limbs. Maximum isometric muscle strength (N) was compared between 1:1 matched BP and UP limbs. Extensor strength was found to be lower in BP limbs than in UP limbs, (-2.9%; p=0.39) but this difference was not statistically significant. Extensor strength was significantly lower in the UP vs. contralateral pain-free limbs (-6.2%; p<0.001). No differences were observed between BP and contralateral painful limbs (0.6%; p=0.87). In conclusion, the current results identify a slight reduction of maximum knee extensor strength in a painful limb, when the contralateral knee is also painful. In contrast to pain-free limbs, this effect did not reach statistical significance, but the overall findings support the concept of central nervous inhibition of muscle strength by contralateral knee pain.

Evaluation of the Combined Application of Neuromuscular Electrical Stimulation and Volitional Contractions on Thigh Muscle Strength, Knee Pain, and Physical Performance in Women at Risk for Knee Osteoarthritis: A Randomized Controlled Trial

BACKGROUND

Knee osteoarthritis (OA) is a leading cause of disability that is associated with quadriceps weakness. However, strengthening in people with or with risk factors for knee OA can be poorly tolerated.

OBJECTIVE

To assess the efficacy of a 12-week low-load exercise program, using a hybrid training system (HTS) that uses the combination of neuromuscular electrical stimulation and volitional contractions, for improving thigh muscle strength, knee pain relief, and physical performance in women with or with risk factors for knee OA.

DESIGN

Randomized, single-blinded, controlled trial.

SETTING

Exercise training laboratory.

PARTICIPANTS

Forty-two women 44-85 years old with risk factors for knee OA.

INTERVENTIONS

Participants randomized to 12 weeks of biweekly low-load resistance training with the HTS or on an isokinetic dynamometer (control).

OUTCOMES

Maximum isokinetic knee extensor torque. Secondary measures included maximum isokinetic knee flexor torque, knee pain (Knee Injury and Osteoarthritis Outcome Score), and timed 20-m walk and chair stand tests.

RESULTS

The HTS and control treatments resulted in muscle strengthening, decreased knee pain, and improved physical performance. HTS group quadriceps and hamstring strength increased by 0.06 ± 0.04 Nm/kg (P > .05) and 0.05 ± 0.02 Nm/kg (P = .02), respectively. Control group quadriceps and hamstring strength increased by 0.03 ± 0.04 Nm/kg (P > .05) and 0.06 ± 0.02 Nm/kg (P = .009), respectively. Knee pain decreased by 11.9 ± 11.5 points (P < .001) for the HTS group and 14.1 ± 15.4 points (P = .001) for the control group. The 20-m walk time decreased by 1.60 ± 2.04 seconds (P = .005) and 0.95 ± 1.2 seconds (P = .004), and chair stand time decreased by 4.8 ± 10.0 seconds (P > .05) and 1.9 ± 4.7 seconds (P > .05) in the HTS and control groups, respectively. These results did not differ statistically between the HTS and control groups.

CONCLUSIONS

These results suggest the HTS is effective for alleviating pain and improving physical performance in women with risk factors for knee OA. However, the HTS does not appear to be superior to low-load resistance training for improving muscle strength, pain relief, or physical function.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02802878.

LEVEL OF EVIDENCE

I.

Affect and Incident Participation Restriction in Adults With Knee Osteoarthritis

OBJECTIVE

Participation restriction, common among people with knee osteoarthritis (OA), may be influenced by affect. We examined the risk of incident participation restriction over 84 months conferred by positive and negative affect among people with knee OA.

METHODS

Participants were from the Multicenter Osteoarthritis Study and had or were at high risk of knee OA. Participation restriction was measured using the Instrumental Role Limitation subscale of the Late-Life Disability Index, and affect was measured using the positive affect and depressed mood subscales of the Center for Epidemiologic Studies Depression Scale. Robust Poisson regression was used to calculate the risk of incident participation restriction over 84 months conferred by combinations of low and high positive and negative affect, adjusting for covariates.

RESULTS

Of 1,810 baseline participants (mean age 62.1 years, 56% female), 470 (26%) had incident participation restriction over 84 months. Participants with low positive affect had 20% greater risk of incident participation restriction than those with high positive affect; participants with high negative affect had 50% greater risk of incident participation restriction compared to those with low negative affect. Participants with both low positive and high negative affect had 80% greater risk of incident participation restriction compared to other combinations of positive and negative affect.

CONCLUSION

Low positive and high negative affect, both alone and in combination, increase the risk of participation restriction among adults with knee OA. Efforts aimed at preventing participation restriction in this population should consider these mood states.

Lower Quadriceps Rate of Force Development Is Associated With Worsening Physical Function in Adults With or at Risk for Knee Osteoarthritis: 36-Month Follow-Up Data From the Osteoarthritis Initiative

OBJECTIVE

To determine the association between quadriceps rate of force development (RFD) and decline in self-reported physical function and objective measures of physical performance.

DESIGN

Longitudinal cohort study.

SETTING

Community-based sample from 4 urban areas.

PARTICIPANTS

Osteoarthritis Initiative participants with or at risk for knee osteoarthritis, who had no history of knee/hip replacement, knee injury, or rheumatoid arthritis (N=2630).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Quadriceps RFD (N/s) was measured during isometric strength testing. Worsening physical function was defined as the minimal clinically important difference for worsening self-reported Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function subscale score, 20-m walk time, and repeated chair stand time over 36 months.

RESULTS

Compared with the slowest tertile of RFD, the fastest tertile had a lower risk for worsening of WOMAC physical function subscale score at 36-month follow-up, with an odds ratio (OR) of .68 (95% confidence interval [CI], .51-.92) after adjustment for age, sex, body mass index, depression, history of chronic diseases, and knee pain. In women, in comparison with the slowest tertile of RFD, the fastest tertile had a lower risk for worsening of WOMAC physical function subscale score at 36-month follow-up, with an adjusted OR of .57 (95% CI, .38-.86). This decreased risk did not reach statistical significance in men (OR, 0.81; 95% CI, 0.52-1.27). No statistically significant associations were detected between baseline RFD and walk or chair stand times.

CONCLUSIONS

Our results indicate that higher RFD is associated with decreased risk for worsening self-reported physical function but not with decreased risk for worsening of physical performance.

Symptoms of Knee Instability as Risk Factors for Recurrent Falls

OBJECTIVE

Whether knee instability contributes to the increased risk of falls and fractures observed in persons with knee osteoarthritis (OA) has not been studied. We examined the association of knee buckling with the risk of falling and fall-related consequences in older adults with, or at high risk for, knee OA.

METHODS

At the 60-month visit of the Multicenter Osteoarthritis Study, men and women ages 55-84 years were asked about knee buckling in the past 3 months and whether they fell when a knee buckled. Falls and fall-related injuries in the past 12 months and balance confidence were assessed at 60 and 84 months. Multivariate logistic regression was used to assess the association of knee buckling with falls and their consequences.

RESULTS

A total of 1,842 subjects (59% women, mean ± SD age 66.9 ± 7.8 years, and body mass index 30.3 ± 5.7) were included. At 60 months 16.8% reported buckling and at 84 months 14.1% had recurrent (≥2) falls. Bucklers at 60 months had a 1.6- to 2.5-fold greater odds of recurrent falls, fear of falling, and poor balance confidence at 84 months. Those who fell when a knee buckled at baseline had a 4.5-fold, 2-fold, and 3-fold increased odds 2 years later of recurrent falls, significant fall injuries, and fall injuries that limited activity, respectively, and were 4 times more likely to have poor balance confidence.

CONCLUSION

Interventions that reduce knee buckling may help prevent falls, fall-related injuries, and adverse psychological consequences of falls in persons with knee OA.

Comparison of tibiofemoral joint space width measurements from standing CT and fixed flexion radiography

The objective of this project was to determine the relationship between medial tibiofemoral joint space width measured on fixed-flexion radiographs and the three-dimensional joint space width distribution on low-dose, standing CT (SCT) imaging. At the 84-month visit of the Multicenter Osteoarthritis Study, 20 participants were recruited. A commercial SCT scanner for the foot and ankle was modified to image knees while standing. Medial tibiofemoral joint space width was assessed on radiographs at fixed locations from 15% to 30% of compartment width using validated software and on SCT by mapping the distances between three-dimensional subchondral bone surfaces. Individual joint space width values from radiographs were compared with three-dimensional joint space width values from corresponding sagittal plane locations using paired t-tests and correlation coefficients. For the four medial-most tibiofemoral locations, radiographic joint space width values exceeded the minimal joint space width on SCT by a mean of 2.0 mm and were approximately equal to the 61st percentile value of the joint space width distribution at each respective sagittal-plane location. Correlation coefficients at these locations were 0.91-0.97 and the offsets between joint space width values from radiographs and SCT measurements were consistent. There were greater offsets and variability in the offsets between modalities closer to the tibial spine. Joint space width measurements on fixed-flexion radiographs are highly correlated with three-dimensional joint space width from SCT. In addition to avoiding bony overlap obscuring the joint, a limitation of radiographs, the current study supports a role for SCT in the evaluation of tibiofemoral OA. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1388-1395, 2017.

Correlations of Medial Joint Space Width on Fixed-Flexed Standing Computed Tomography and Radiographs With Cartilage and Meniscal Morphology on Magnetic Resonance Imaging

OBJECTIVE

To assess whether medial tibiofemoral joint space width (JSW) on 3-dimensional (3-D) standing computed tomography (SCT) correlates more closely with magnetic resonance imaging cartilage morphology (CM) and meniscal scores than does radiographic 2-D JSW.

METHODS

Participants in the Multicenter Osteoarthritis Study, who had standing fixed-flexion posteroanterior knee radiographs, were recruited. Medial tibiofemoral 3-D JSW on SCT and 2-D JSW on fixed-flexion radiographs were compared with medial tibiofemoral cartilage and meniscal morphology using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Associations between the area of the articular surface with 3-D JSW <2.5 mm on SCT, radiographic minimal 2-D JSW, and the WORMS-CM and meniscal scores were assessed using Spearman's rho.

RESULTS

For the 19 participants included (33 knees), mean ± SD age was 66.9 ± 5.4 years, body mass index was 29.5 ± 4.4 kg/m(2) , 42.1% of participants were female, and the Kellgren/Lawrence grades were 0 (21.2%), 1 (36.4%), 2 (18.2%), and 3 (24.2%). The articular surface area with 3-D JSW <2.5 mm on SCT correlated with WORMS-CM scores for the central medial tibia (rs  = 0.84, P < 0.001), central medial femur (rs  = 0.60, P < 0.007), and posterior medial meniscal tear (rs  = 0.39, P < 0.026), as did other cut points for 3-D JSW. Correlations with radiographic minimal 2-D JSW were -0.66, -0.52, and -0.40, respectively, differing from SCT only for tibial cartilage (P = 0.001).

CONCLUSION

Greater surface area with a low JSW, measured by SCT, correlates more strongly with the severity of tibial cartilage lesions, while correlating with medial femoral cartilage and meniscal damage to a similar extent as radiographic minimal JSW. SCT may enable valid stratification of participants in clinical trials, through quickly and inexpensively characterizing osteoarthritis features.

Perceived Community Environmental Factors and Risk of Five-Year Participation Restriction Among Older Adults With or at Risk of Knee Osteoarthritis

OBJECTIVE

Older adults with knee osteoarthritis (OA) who live in environments with mobility barriers may be at greater risk of developing participation restrictions, defined as difficulties in engagement in life situations. We investigated the risk of participation restriction over 5 years due to self-reported environmental features among older adults with knee OA.

METHODS

Participants from the Multicenter Osteoarthritis (MOST) Study self-reported participation at baseline, 30 months, and 60 months using the instrumental role subscale of the Late Life Disability Index (LLDI). Data on self-reported environmental features were from the Home and Community Environment questionnaire administered in the MOST Knee Pain and Disability study, an ancillary study of MOST. The relative risks (RRs) of developing participation restriction at 60 months, indicated by an LLDI score <67.6 out of a possible 100, due to reported high community mobility barriers and high transportation facilitators, were calculated using robust Poisson regression, adjusting for covariates.

RESULTS

Sixty-nine of the 322 participants (27%) developed participation restriction by 60 months. Participants reporting high community mobility barriers at baseline had 1.8 times the risk (95% confidence interval [95% CI] 1.2-2.7) of participation restriction at 60 months, after adjusting for covariates. Self-report of high transportation facilitators at baseline resulted in a reduced but statistically nonsignificant risk of participation restriction at 60 months (RR 0.7, 95% CI 0.4-1.1).

CONCLUSION

Higher perceived environmental barriers impact the risk of long-term participation restriction among older adults with or at risk of knee OA. Approaches aimed at reducing the development of participation restrictions in this population should consider decreasing environmental barriers.

The Effect of Widespread Pain on Knee Pain Worsening, Incident Knee Osteoarthritis (OA), and Incident Knee Pain: The Multicenter OA (MOST) Study

OBJECTIVE

Whether widespread pain (WSP) affects the risk of developing knee pain or knee osteoarthritis (OA) is unknown and could enhance understanding of pain mechanisms in OA.

METHODS

Subjects from the Multicenter OA (MOST) study, a US National Institutes of Health-funded prospective cohort of older adults with or at risk of knee OA, were characterized regarding WSP, defined as pain above and below the waist on both sides of the body and axially using a standard homunculus, excluding knee pain at 60 months (baseline). Followup occurred 2 years later. We assessed the relation of WSP to odds of knee pain worsening (≥ 2-point increase in the Western Ontario and McMaster Universities Arthritis Index pain subscale) using logistic regression, and to odds of incident radiographic knee OA (ROA; Kellgren-Lawrence arthritis scale ≥ grade 2 of either knee among those free of ROA at baseline) and incident consistent frequent knee pain (CFKP; knee pain on most days during the past month among participants free of knee pain at baseline) in 1 or both knees using multinomial regression adjusting for potential confounders.

RESULTS

There were 1752 participants available for analysis [mean age (SD) 67.0 yrs (7.7), body mass index 30.5 kg/m2 (5.9), 59% women]. Baseline presence of WSP was not associated with worsened knee pain (adjusted OR 1.15, 95% CI 0.89-1.48, p = 0.30), ROA (adjusted OR 0.86, 95% CI 0.46-1.63, p = 0.65), or incident CFKP (adjusted OR 1.69, 95% CI 0.96-2.96, p = 0.07).

CONCLUSION

WSP was not significantly associated with worsening knee pain, incident ROA, or CFKP. Development of knee pain and ROA does not appear to be influenced by underlying WSP.

Test-retest reliability of tibiofemoral joint space width measurements made using a low-dose standing CT scanner

OBJECTIVE

To determine the test-retest reliability of knee joint space width (JSW) measurements made using standing CT (SCT) imaging.

SUBJECTS AND METHODS

This prospective two-visit study included 50 knees from 30 subjects (66% female; mean ± SD age 58.2 ± 11.3 years; BMI 29.1 ± 5.6 kg/m²; 38% KL grade 0-1). Tibiofemoral geometry was obtained from bilateral, approximately 20° fixed-flexed SCT images acquired at visits 2 weeks apart. For each compartment, the total joint area was defined as the area with a JSW <10 mm. The summary measurements of interest were the percentage of the total joint area with a JSW less than 0.5-mm thresholds between 2.0 and 5.0 mm in each tibiofemoral compartment. Test-retest reliability of the summary JSW measurements was assessed by intraclass correlation coefficients (ICC 2,1) for the percentage area engaged at each threshold of JSW and root-mean-square errors (RMSE) were calculated to assess reproducibility.

RESULTS

The ICCs were excellent for each threshold assessed, ranging from 0.95 to 0.97 for the lateral and 0.90 to 0.97 for the medial compartment. RMSE ranged from 1.1 to 7.2% for the lateral and from 3.1 to 9.1% for the medial compartment, with better reproducibility at smaller JSW thresholds.

CONCLUSION

The knee joint positioning protocol used demonstrated high day-to-day reliability for SCT 3D tibiofemoral JSW summary measurements repeated 2 weeks apart. Low-dose SCT provides a great deal of information about the joint while maintaining high reliability, making it a suitable alternative to plain radiographs for evaluating JSW in people with knee OA.

The Association of Vibratory Perception and Muscle Strength With the Incidence and Worsening of Knee Instability: The Multicenter Osteoarthritis Study

OBJECTIVE

To examine neuromuscular factors that predict the incidence and progression of knee instability symptoms in older adults with or at high risk of knee osteoarthritis (OA).

METHODS

At the 60-month clinic visit, participants in the Multicenter Osteoarthritis Study underwent evaluation of quantitative vibratory sense at the knee and isokinetic quadriceps muscle strength. At this 60-month visit, participants were also asked about knee buckling and sensations of knee shifting or slipping without buckling in the past 3 months and then were asked the same questions at the 72- and 84-month follow-up visits. We performed a person-based analysis using Poisson regression analysis with robust error variance to estimate adjusted relative risks (RRs) for the association of vibratory sense and muscle strength with the incidence and worsening of knee slipping/shifting, buckling, and overall knee instability symptoms (either buckling or knee shifting/slipping), with adjustment for relevant confounders.

RESULTS

A total of 1,803 participants (61% women) were included. Approximately one-third of the participants reported incident or worsening of instability symptoms over the study period. After adjustment for relevant confounders, better vibratory acuity (adjusted RR 0.78, 95% confidence interval [95% CI] 0.56-1.09), P = 0.020 for trend) and greater quadriceps strength (adjusted RR 0.53, 95% CI 0.38-0.75, P < 0.001) protected against incident knee instability symptoms. Greater quadriceps strength (adjusted RR 0.73, 95% CI 0.58-0.92, P = 0.008) also protected against worsening of knee instability symptoms.

CONCLUSION

Vibratory acuity and quadriceps muscle strength are important predictors of the incidence and worsening of knee instability over 2 years. These neuromuscular factors are potentially modifiable and should be considered in interventional studies of instability in persons with or at risk of knee OA.

Effect of Knee Extensor Strength on Incident Radiographic and Symptomatic Knee Osteoarthritis in Individuals With Meniscal Pathology: Data From the Multicenter Osteoarthritis Study

OBJECTIVE

High knee extensor strength may be important to protect against the development of knee osteoarthritis (OA) in populations at elevated risk, such as individuals with meniscal pathology. We investigated the extent to which high knee extensor muscle strength was associated with a decreased risk of developing radiographic or symptomatic knee OA in individuals with medial meniscal pathology.

METHODS

We studied knees that at the baseline visit of the Multicenter Osteoarthritis Study had medial meniscal pathology but did not have radiographic knee OA (373 knees in 373 participants) or symptomatic knee OA (combination of radiographic knee OA and frequent knee symptoms; 531 knees in 531 participants). Isokinetic knee extensor strength was measured at baseline, and participants were followed for development of incident radiographic knee OA or incident symptomatic knee OA at 84 months. Separate binomial regression analyses with robust SEs adjusted for age, history of knee surgery, physical activity level, and clinic site were conducted for men and women.

RESULTS

High knee extensor strength (normalized by allometric scaling) was associated with a reduced risk of radiographic knee OA in women (relative risk [RR] 0.52, 95% confidence interval [95% CI] 0.29-0.94) but not in men (RR 0.56, 95% CI 0.27-1.16). High knee extensor strength did not protect against the development of symptomatic knee OA, either in women or men.

CONCLUSION

The results only partly confirm the hypothesis that high knee extensor muscle strength protects against later development of knee OA in individuals with medial meniscal pathology.