The Natural History of Knee Osteoarthritis Pain Experience and Risk Profiles.

The study aimed to characterize the natural history of the pain experience, concurrently considering intermittent and constant pain over 4 years, and determine baseline factors associated with unfavorable trajectories in individuals with chronic knee pain. The Osteoarthritis Initiative (OAI) is a prospective, observational study of people with or at higher risk for knee osteoarthritis. The Intermittent and Constant Osteoarthritis Pain (ICOAP) was assessed annually at 48-to-96-month OAI visits. Twenty-eight baseline sociodemographic, knee-specific, and health-related characteristics were assessed. Group-based dual-trajectory modeling identified pain experience patterns indicated by ICOAP intermittent and constant pain scores over 4 years. Multivariable multinomial logistic regression models determined baseline factors associated with membership in each dual-trajectory group. Four longitudinal pain experience patterns were identified (n = 3,584, mean age = 64.8 [standard deviation 9.0] years, BMI = 28.6 [5.0] kg/m2; 57.9% women). Group 1 (37.7%) had minimal intermittent and no constant pain; Group 2 (35.1%) had mild intermittent and no constant pain; Group 3 (18.5%) had mild intermittent and low-grade constant pain; and Group 4 (8.7%) had moderate intermittent and constant pain. Baseline widespread pain, knee stiffness, back pain, hip pain, ankle pain, obesity, depressive symptoms, more advanced radiographic disease, and analgesic use were each associated with an increased risk of membership in less favorable Groups 2, 3, and 4. These distinct courses of pain experience may be driven by different underlying pain mechanisms. The benchmarked ICOAP scores could be used to stratify patients and tailor management. Addressing and preventing the development of modifiable risks (eg, widespread pain and knee joint stiffness) may reduce the chance of belonging to unfavorable dual-trajectory groups. PERSPECTIVE: Concurrently tracking intermittent versus constant pain experience, group-based dual-trajectory modeling identified 4 distinct pain experience patterns over 4 years. The benchmarked ICOAP scores in these dual trajectories could aid in stratifying patients for tailored management strategies and intensity of care.

Ambulatory support moment contribution patterns and MRI-detected tibiofemoral and patellofemoral disease worsening in adults with knee osteoarthritis: A preliminary study.

We investigated whether baseline sagittal-plane ankle, knee, and hip contribution to the total support moment (TSM) are each associated with baseline-to-2-year tibiofemoral and patellofemoral tissue damage worsening in adults with knee osteoarthritis. Ambulatory lower-limb kinetics were captured and computed. TSM is the sum of ankle, knee, and hip extensor moments at each instant during gait. Ankle, knee, and hip contributions to TSM were computed as joint moments divided by TSM, expressed as percentages. Participants underwent MRI of both knees at baseline and 2 years later. Logistic regression models assessed associations of baseline ankle contribution to TSM with baseline-to-2-year cartilage damage and bone marrow lesion worsening, adjusted for age, sex, BMI, gait speed, disease severity, and pain. We used similar analytic approaches for knee and hip contributions to TSM. Sample included 391 knees from 204 persons (age[SD]: 64[10] years; 76.5% women). Greater ankle contribution may be associated with increased odds of tibiofemoral cartilage damage worsening (OR = 2.38; 95% CI: 1.02-5.57) and decreased odds of patellofemoral bone marrow lesion worsening (OR = 0.14; 95% CI: 0.03-0.73). The ORs for greater knee contribution were in the protective range for tibiofemoral compartment and in the deleterious range for patellofemoral. Greater hip contribution may be associated with increased odds of tibiofemoral worsening (OR = 2.71; 95% CI: 1.17-6.30). Greater ankle contribution to TSM may be associated with baseline-to-2-year tibiofemoral worsening, but patellofemoral tissue preservation. Conversely, greater knee contribution may be associated with patellofemoral worsening, but tibiofemoral preservation. Preliminary findings illustrate potential challenges in developing biomechanical interventions beneficial to both tibiofemoral and patellofemoral compartments.

Knee Confidence Trajectories Over Eight Years and Factors Associated With Poor Trajectories in Individuals With or at Risk for Knee Osteoarthritis.

OBJECTIVE: To identify distinct trajectories of lack of knee confidence over an 8-year follow-up period and to examine baseline factors associated with poor trajectories in individuals with or at risk for knee osteoarthritis (OA). METHODS: The Osteoarthritis Initiative is a prospective cohort study of individuals with or at high risk for knee OA. Confidence in the knees was assessed within the Knee Injury and Osteoarthritis Outcome Score instrument querying how much the individual is troubled by lack of confidence in his/her knee(s), rated as not-at-all (score = 0), mildly (score = 1), moderately (score = 2), severely (score = 3), and extremely (score = 4) troubled, reported annually from baseline to 96 months. Lack of knee confidence was defined as a score of ≥2. We used latent class models to identify subgroups that share similar underlying knee confidence trajectories over an 8-year period and multivariable multinomial logistic regression models to examine baseline factors associated with poor trajectories. RESULTS: Among 4,515 participants (mean ± SD age 61.2 ± 9.2 years, mean ± SD BMI 28.6 ± 4.8 kg/m2 ; 2,640 [58.5%] women), 4 distinct knee confidence trajectories were identified: persistently good (65.6%); declining (9.1%); poor, improving (13.9%); and persistently poor (11.4%). Baseline predictors associated with persistently poor confidence (reference: persistently good) were younger age, male sex, higher body mass index (BMI), depressive symptoms, more advanced radiographic disease, worse knee pain, weaker knee extensors, history of knee injury and surgery, and reported hip and/or ankle pain. CONCLUSION: Findings suggest the dynamic nature of self-reported knee confidence and that addressing modifiable factors (e.g., BMI, knee strength, depressive symptoms, and lower extremity pain) may improve its long-term course.

Varus Thrust and Incident and Progressive Knee Osteoarthritis.

OBJECTIVE: To determine if varus thrust, a bowing out of the knee during gait (i.e., the first appearance or worsening of varus alignment during stance), is associated with incident and progressive knee osteoarthritis (OA), we undertook an Osteoarthritis Initiative ancillary study. We further considered hypothesized associations adjusted for static alignment, anticipating some attenuation. METHODS: Gait was observed for the presence of thrust by 1 of 2-3 examiners per study site at 4 sites. In eligible knees, incident OA was defined as subsequent incident Kellgren/Lawrence grade ≥2, whole- and partial-grade medial joint space narrowing (JSN), and annualized loss of joint space width (JSW); progression was defined as medial JSN and JSW loss. Outcome measures were assessed for up to 7 years of follow-up. Analyses were knee-level, using multivariable logistic and linear regression with generalized estimating equations to account for between-limb correlation. RESULTS: The incident OA sample included 4,187 knees (2,610 persons); the progression sample included 3,421 knees (2,284 persons). In knees with OA, thrust was associated with progression as assessed by each outcome measure, with adjustment for age, sex, body mass index, and pain on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale. In knees without OA, varus thrust was not associated with incident OA or other outcomes. After adjustment for alignment, the thrust-progression association was attenuated, but an independent association persisted for partial-grade JSN and JSW loss outcome models. WOMAC pain and alignment were consistently associated with all outcome measures. Within the stratum of varus knees, thrust was associated with an increased risk of progression. CONCLUSION: Varus thrust visualized during gait is associated with knee OA progression and should be a target of intervention development.

Knee Flexion and Daily Activities in Patients following Total Knee Replacement: A Comparison with ISO Standard 14243.

Walking is only one of many daily activities performed by patients following total knee replacement (TKR). The purpose of this study was to examine the hypotheses (a) that subject activity characteristics are correlated with knee flexion range of motion (ROM) and (b) that there is a significant difference between the subject's flexion/extension excursion throughout the day and the ISO specified input for knee wear testing. In order to characterize activity, the number of walking and stair stepping cycles, the time spent with dynamic and stationary activities, the number of activity sequences, and the knee flexion/extension excursion of 32 TKR subjects were collected during daily activity. Flexion/extension profiles were compared with the ISO 14243 simulator input profile using a level crossing classification algorithm. Subjects took an average of 3102 (range: 343-5857) walking cycles including 65 (range: 0-319) stair stepping cycles. Active and passive ROMs were positively correlated with stair walking time, stair step counts, and stair walking sequences. Simulated knee motion according to ISO showed significantly fewer level crossings at the flexion angles 20-40° and beyond 50° than those measured with the monitor. This suggests that implant wear testing protocols should contain more cycles and a variety of activities requiring higher knee flexion angles with incorporated resting/transition periods to account for the many activity sequences.

Knee Instability and Basic and Advanced Function Decline in Knee Osteoarthritis.

OBJECTIVE: Manifestations of instability in knee osteoarthritis (OA) include low overall knee confidence, low confidence that the knees will not buckle, buckling, and excessive motion during gait. Confidence and buckling may particularly influence activity choices, contributing to events leading to disability. Buckling is more likely to affect advanced than basic functional tasks. In this prospective longitudinal study, we tested the hypothesis that overall knee confidence, buckling confidence, buckling, and frontal plane motion during gait are associated with advanced 2-year function outcomes in persons with knee OA. METHODS: Persons with knee OA were queried about overall knee confidence (higher score = worse confidence), buckling confidence, and knee buckling, and underwent quantitative gait analysis to quantify varus-valgus excursion and angular velocity. Physical function was assessed using the Late-Life Function and Disability Instrument Basic and Advanced Lower Extremity Domain scores. Logistic regression was used to evaluate the relationship between baseline instability measures and baseline-to-2-year function outcome, adjusting for potential confounders. RESULTS: The sample was comprised of 212 persons (mean age 64.6 years, 76.9% women). Buckling was significantly associated with poor advanced function outcome (adjusted odds ratio [OR] 2.08, 95% confidence interval [95% CI] 1.03-4.20) but not basic function outcome. Overall knee confidence was significantly associated with advanced outcome (adjusted OR 1.65, 95% CI 1.01-2.70), while associations between buckling confidence and both outcomes approached significance. Neither varus-valgus excursion nor angular velocity during gait was associated with either outcome. CONCLUSION: Knee buckling and low knee confidence were each associated with poor 2-year advanced function outcomes. Current treatment does not address these modifiable factors; interventions to address them may improve outcome in knee OA.

Factors associated with pain experience outcome in knee osteoarthritis.

OBJECTIVE: Few strategies to improve pain outcome in knee osteoarthritis (OA) exist in part because how best to evaluate pain over the long term is unclear. Our objectives were to determine the frequency of a good pain experience outcome based on previously formulated OA pain stages and test the hypothesis that less depression and pain catastrophizing and greater self-efficacy and social support are each associated with greater likelihood of a good outcome. METHODS: Study participants, all with knee OA, reported pain stage at baseline and 2 years. Baseline assessments utilized the Geriatric Depression Scale, Pain Catastrophizing Scale, Arthritis Self-Efficacy Scale, and Medical Outcomes Study social support survey. Using pain experience stages, good outcome was defined as persistence in or movement to no pain or stage 1 (predictable pain, known trigger) at 2 years. A multivariable logistic regression model was developed to identify independent predictors of a good outcome. RESULTS: Of 212 participants, 136 (64%) had a good pain outcome and 76 (36%) a poor pain outcome. In multivariable analysis, higher self-efficacy was associated with a significantly higher likelihood of good outcome (adjusted odds ratio [OR] 1.14 [95% confidence interval (95% CI) 1.04-1.24]); higher pain catastrophizing was associated with a significantly lower likelihood of good outcome (adjusted OR 0.88 [95% CI 0.83-0.94]). CONCLUSION: This stage-based measure provides a meaningful and interpretable means to assess pain outcome in knee OA. The odds of a good 2-year outcome in knee OA were lower in persons with greater pain catastrophizing and higher in persons with greater self-efficacy. Targeting these factors may help to improve pain outcome in knee OA.

Knee confidence as it relates to physical function outcome in persons with or at high risk of knee osteoarthritis in the osteoarthritis initiative.

OBJECTIVE: To evaluate whether low knee confidence at baseline is associated with poor baseline-to-3-year physical function outcome in the Osteoarthritis Initiative. METHODS: Knee confidence was assessed using an item from the Knee Injury and Osteoarthritis Outcome Score instrument. Physical function was assessed using self-report measures (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC] function score and Short Form 12 physical component scale) and performance-based measures (20-meter walk and chair stand test). Poor function outcome was defined as moving into a worse function group or remaining in the 2 worst function groups between baseline and 3 years. Logistic regression was used to evaluate the relationship between baseline knee confidence level and poor baseline-to-3-year function outcome, adjusting for potential confounders. RESULTS: The sample included 3,975 men and women with or at high risk of developing osteoarthritis of the knee, of whom 37-53% had poor baseline-to-3-year function outcome. For both self-report measures, increasingly worse knee confidence was associated with a greater risk of poor function outcome, and trend tests supported a graded response (e.g., the adjusted odds ratios [95% confidence intervals] for the WOMAC function score for worsening confidence categories were 1.26 [1.07-1.49], 1.43 [1.16-1.77], and 2.05 [1.49-2.82], P for trend <0.0001). Similar associations between confidence and performance-based function outcome were observed, but statistical significance did not persist in adjusted analyses. Factors independently associated with poor function outcome for all 4 outcome measures were depressive symptoms, comorbidity, body mass index, and joint space narrowing. CONCLUSION: These findings indicate that worse knee confidence at baseline is independently associated with greater risk of poor function outcome by self-report measures, with evidence of a graded response; the relationship with performance measures is not significant in fully adjusted models.

Varus-valgus alignment: reduced risk of subsequent cartilage loss in the less loaded compartment.

OBJECTIVE: Varus-valgus alignment has been linked to subsequent progression of osteoarthritis (OA) within the mechanically stressed (medial for varus, lateral for valgus) tibiofemoral compartment. Cartilage data from the off-loaded compartment are sparse. The purpose of this study was to examine our hypotheses that neutral and valgus (versus varus) knees each have reduced odds of cartilage loss in the medial subregions and that neutral and varus (versus valgus) knees each have reduced odds of cartilage loss in the lateral subregions. METHODS: Patients with knee OA underwent knee magnetic resonance imaging at baseline and 2 years. The mean cartilage thickness was quantified within 5 tibial and 3 femoral subregions. We used logistic regression with generalized estimating equations to analyze the relationship between baseline alignment and subregional cartilage loss at 2 years, adjusting for age, sex, body mass index, and disease severity. RESULTS: A reduced risk of cartilage loss in the medial subregions was associated with neutral (versus varus) alignment (external tibial, central femoral, external femoral) and with valgus (versus varus) alignment (central tibial, external tibial, central femoral, external femoral). A reduced risk of cartilage loss in the lateral subregions was associated with neutral (versus valgus) alignment (central tibial, internal tibial, posterior tibial) and with varus (versus valgus) alignment (central tibial, external tibial, posterior tibial, external femoral). CONCLUSION: Neutral and valgus alignment were each associated with a reduction in the risk of subsequent cartilage loss in certain medial subregions and neutral and varus alignment with a reduction in the risk of cartilage loss in certain lateral subregions. These results support load redistribution as an in vivo mechanism of the long-term alignment effects on cartilage loss in knee OA.

Subregional effects of meniscal tears on cartilage loss over 2 years in knee osteoarthritis.

OBJECTIVES: Meniscal tears have been linked to knee osteoarthritis progression, presumably by impaired load attenuation. How meniscal tears affect osteoarthritis is unclear; subregional examination may help to elucidate whether the impact is local. This study examined the association between a tear within a specific meniscal segment and subsequent 2-year cartilage loss in subregions that the torn segment overlies. METHODS: Participants with knee osteoarthritis underwent bilateral knee MRI at baseline and 2 years. Mean cartilage thickness within each subregion was quantified. Logistic regression with generalised estimating equations were used to analyse the relationship between baseline meniscal tear in each segment and baseline to 2-year cartilage loss in each subregion, adjusting for age, gender, body mass index, tear in the other two segments and extrusion. RESULTS: 261 knees were studied in 159 individuals. Medial meniscal body tear was associated with cartilage loss in external subregions and in central and anterior tibial subregions, and posterior horn tear specifically with posterior tibial subregion loss; these relationships were independent of tears in the other segments and persisted in tibial subregions after adjustment for extrusion. Lateral meniscal body and posterior horn tear were also associated with cartilage loss in underlying subregions but not after adjustment for extrusion. Cartilage loss in the internal subregions, not covered by the menisci, was not associated with meniscal tear in any segment. CONCLUSION: These results suggest that the detrimental effect of meniscal tears is not spatially uniform across the tibial and femoral cartilage surfaces and that some of the effect is experienced locally.

Time course and extent of functional recovery during the first postoperative year after minimally invasive total hip arthroplasty with two different surgical approaches--a randomized controlled trial.

UNLABELLED: While others have reported short-term comparisons between various minimally invasive surgical (MIS) approaches to total hip arthroplasty (THA) and their conventional analogues, longer-term data is lacking, as is information indicating whether MIS approaches to THA provide a biomechanically complete recovery. Furthermore, different MIS approaches have not been compared. Our approaches of interest were a one-incision modified Watson-Jones, and a two-incision approach. HYPOTHESES: (1) There are significant differences in gait recovery patterns between the two surgical groups and (2) THA subjects have significant differences in function one year after surgery compared to control subjects. To test these hypotheses, THA candidates (n=26) were randomized to receive one of these MIS approaches and evaluated preoperatively, and postoperatively at 3 weeks, and at 3, 6 and 12 months. Evaluations included three-dimensional gait analysis and 24-hour step-counts. The same data were obtained from 25 control subjects. Recovery time-course was assessed using repeated measures ANOVA. T-tests were used to compare controls with the pooled group of THA subjects. We found no differences between the two THA surgical groups regarding the time-course of recovery (p≥0.591). Although recovery was statistically complete by 3 months postoperatively for all variables, there were significant differences from controls at 12 months. Most notably, the external hip adduction moment, which reflects hip abductor function, was more than one standard deviation below normal (p<0.001). THA subject inactivity could not explain the gait differences, since one year after surgery daily step counts were not significantly different from controls (p=0.346). More work is necessary to determine ways to improve biomechanical outcomes for today's patients with high expectations for function and implant longevity.

Denuded subchondral bone and knee pain in persons with knee osteoarthritis.

OBJECTIVE: It is unclear how articular cartilage loss contributes to pain in patients with knee osteoarthritis (OA). Full-thickness cartilage defects expose the subchondral bone plate. The relationship between denuded bone and pain has not been examined. The aim of this study was to investigate whether the percent of denuded bone is associated with moderate-to-severe knee pain or frequent knee pain and longitudinally with frequent knee pain 2 years after the baseline evaluation. METHODS: We studied 182 persons with knee OA (305 knees). Applying specialized magnetic resonance imaging techniques, manual segmentation was used to compute cartilage-covered and denuded bone areas for each surface. Moderate-to-severe knee pain was defined as a score of >or=40 mm on a knee-specific 100-mm visual analog scale, and frequent knee pain was defined as pain on most days during the past month. Logistic regression and generalized estimating equations were used in analyses, adjusting for age, sex, body mass index, and bone marrow lesions. RESULTS: Cross-sectional analyses revealed that moderate-to-severe knee pain was associated with percent denuded bone in the medial compartment (adjusted odds ratio [OR] 3.90, 95% confidence interval [95% CI] 1.33-11.47), in the medial and patellar surfaces together, and in the lateral and patellar surfaces. Frequent knee pain was associated with percent denuded bone in the patellar surface (adjusted OR 3.11, 95% CI 1.24-7.81), in the medial and patellar surfaces, and in the lateral and patellar surfaces. Longitudinal analyses (in 168 knees without frequent knee pain at baseline) revealed that percent denuded bone in the medial and patellar surfaces was associated with frequent incident knee pain (adjusted OR 4.19, 95% CI 1.56-11.22). CONCLUSION: These results support a relationship between subchondral bone plate exposure and prevalent and incident knee pain in patients with knee OA.

Knee joint loading differs in individuals with mild compared with moderate medial knee osteoarthritis.

OBJECTIVE: To compare the knee joint loading patterns in individuals with differing radiographic grades of knee osteoarthritis (OA) for characterization of the mechanical implications of different structural states, and to compare the knee adduction angular impulse, a measure of gait complementary to the commonly used peak knee adduction moment. METHODS: Asymptomatic subjects (those without knee OA) having a Kellgren/Lawrence (K/L) radiographic severity grade of 0 or 1 (n = 28) and subjects with symptomatic knee OA having K/L grades of 2 (n = 66) or 3 (n = 23) were recruited. Gait analysis was used to calculate the peak external knee adduction moment and the external knee adduction angular impulse for the whole stance and for the 4 subdivisions of stance. RESULTS: Both the peak knee adduction moment and the knee adduction angular impulse increased with K/L radiographic grade (P < 0.05). However, only the knee adduction angular impulse differed between subjects with moderate (grade 3) and those with mild (grade 2) radiographic knee OA (P < 0.05). CONCLUSION: The differences between mild and moderate symptomatic radiographic knee OA are not only structural but also functional, based on the magnitude of load in the medial knee joint. Moreover, knee adduction angular impulse provides additional information beyond that available from the peak knee adduction moment, and may therefore be an important gait parameter to include in OA research. These findings are important for our understanding of the pathophysiologic mechanisms of OA.

A biomechanical approach to musculoskeletal disease.

The importance of biomechanical factors in musculoskeletal disease may be appreciated in the clinical characteristics and pathophysiology of joint degeneration in osteoarthritis. The biomechanical characteristics of the neuromuscular system are integral in determining the function and stability of the synovial joint and in mediating the biochemical structure of articular cartilage. Alterations in the neuromuscular system including abnormal gait and dynamic joint loading patterns as well as muscle strength and proprioception deficits have been independently studied and associated with osteoarthritis. These factors have close functional and physiological interactions. Nevertheless, specific relations between muscle strength and proprioception and their independent contributions to dynamic joint loading are not yet clear. Targeted interventions to moderate these factors may, in the future, be a therapeutic option for the management of osteoarthritis.

Dynamic loads are determinants of peak bone mass.

This study investigated the association between non-invasive measurements of bone mass and markers of dynamic and static hip joint loads in subjects expected to be at peak bone mass. The bone mineral density (BMD) and bone mineral content (BMC) of three proximal femoral sites (neck, greater trochanter, and total) were measured by dual energy X-ray absorptiometry, and the peak external joint moments at the hip during walking and jogging were calculated from gait analyses of 31 normal human subjects ranging in age from 30 to 49 years (18 females, 13 males). Various multiple regression analyses were performed to determine how much of the variance in BMD and BMC was explained by height, body mass, and the peak hip joint moments. In total, the models explained up to 40% of the variance in BMD and 58% of the variance in BMC. Inclusion of height or body mass did not increase the explanatory power of the models for BMD and explained no more than 8% of the total variance in BMC once the joint moments from walking were allowed to enter the models. These data support the hypothesis that variance in peak bone mass is associated with variance in dynamic hip loads largely independent of the effect of static factors such as height and body mass.

Normalization of joint moments during gait: a comparison of two techniques.

Joint moments are commonly used to characterize gait. Factors like height and weight influence these moments. This study determined which of two commonly used normalization methods, body mass or body weight times height, most reduced the effects of height and weight on peak hip, knee, and ankle external moments during walking. The effectiveness of each normalization method in reducing gender differences was then tested. Gait data from 158 normal subjects were analyzed using unnormalized values, body mass normalized values, and body weight times height normalized values. Without normalization, height or weight accounted for 7-82% of the variance in all 10 peak components of the moments. With normalization, height and weight accounted for at most 6% of the variance with the exception of the hip adduction moment normalized by body weight times height and the ankle dorsiflexion moment normalized by body mass. For the hip adduction moment normalized by body weight times height, height still accounted for 13% of the variance (p<0.001) and for the ankle dorsiflexion moment normalized by body mass, 22% of the variance (p<0.001). After normalization, significant differences between males and females remained for only two out of 10 moments with the body weight times height method compared to six out of 10 moments with the body mass method. When compared to the unnormalized data, both normalization methods were highly effective in reducing height and weight differences. Even for the two cases where one normalization method was less effective than the other (hip adduction-body weight times height; ankle dorsiflexion-body mass) the normalization process reduced the variance ascribed to height or weight by 48% and 63%, respectively, as compared to the unnormalized data.