Multicenter Osteoarthritis Study Research Articles

SAT0319 Prediction models for progression of knee osteoarthritis in the multicenter osteoarthritis study (MOST)

BackgroundAlthough individual risk factors for incident and progressive knee osteoarthritis (OA) have been identified, less is known about models to predict progression of knee OA.ObjectivesA prospective cohort study was conducted...

FRI0310 Meniscal damage of the posterior horns and associated localized synovitis detected on contrast-enhanced MRI: The most study

BackgroundSynovitis in osteoarthritis (OA) is thought to be a secondary phenomenon related to intraarticular tissue damage including the meniscus.The most frequent location of meniscal damage is the posterior horn of...

OP0029 Medial meniscal root tears are associated with medial meniscal extrusion and medial tibiofemoral cartilage damage – the most study

BackgroundThe meniscal root is a ligamentous structure that anchors the posterior horn of the meniscus to the tibial plateau. The association of isolated meniscal root tears with progression of osteoarthritis...

Medial Posterior Meniscal Root Tears Are Associated with Development or Worsening of Medial Tibiofemoral Cartilage Damage: The Multicenter Osteoarthritis Study

To assess the association of meniscal root tear with the development or worsening of tibiofemoral cartilage damage. Institutional review board approval and written informed consent from all subjects were obtained. A total of 596 knees with radiographically depicted osteoarthritis were randomly selected from the Multicenter Osteoarthritis study cohort. Cartilage damage was semiquantitatively assessed by using the Whole-Organ Magnetic Resonance Imaging Score (WORMS) system (grades 0-6). Subjects were separated into three groups: root tear only, meniscal tear without root tear, and neither meniscal nor root tear. A log-binomial regression model was used to calculate the relative risks for knees to develop incident or progressing cartilage damage in the root tear group and the meniscal tear group, with the no tear group serving as a reference. In the medial tibiofemoral joint, there were 37 knees with isolated medial posterior root tear, 294 with meniscal tear without root tear, and 264 without meniscal or root tear. There were only two lateral posterior root tears, and no anterior root tears were found. Thus, the focus was on the medial posterior root tear. The frequency of severe cartilage damage (WORMS ≥ 5) was higher in the group with root tear than in the group without root or meniscal tear (76.7% vs 19.7%, P < .0001) but not in the group with meniscal but no root tear (76.7% vs 65.2%, P = .055). Longitudinal analyses included 33 knees with isolated medial posterior root tear, 270 with meniscal tear, and 245 with no tear. Adjusted relative risk of cartilage loss was 2.03 (95% confidence interval [CI]: 1.18, 3.48) for the root tear group and 1.84 (95% CI: 1.32, 2.58) for the meniscal tear group. Isolated medial posterior meniscal root tear is associated with incident and progressive medial tibiofemoral cartilage loss.

Reliability of a uni-compartmental scale for the radiographic evaluation of knee arthritis: data from the multicenter osteoarthritis study

Reliability of a uni-compartmental scale for the radiographic evaluation of knee arthritis: data from the multicenter osteoarthritis study

Stance and single support time asymmetry identify unilateral knee OA and the involved limb: the multicenter osteoarthritis study

Stance and single support time asymmetry identify unilateral knee OA and the involved limb: the multicenter osteoarthritis study

Vitamin K Deficiency Is Associated with Incident Knee Osteoarthritis

BackgroundOsteoarthritis is the most common form of arthritis, with knee osteoarthritis being the leading cause of lower extremity disability among older adults in the US. There are no treatments available to prevent the structural pathology of osteoarthritis. Because of vitamin K's role in regulating skeletal mineralization, it has potential to be a preventative option for osteoarthritis. We therefore examined the relation of vitamin K to new-onset radiographic knee osteoarthritis and early osteoarthritis changes on magnetic resonance imaging (MRI). MethodsSubjects from the Multicenter Osteoarthritis (MOST) Study had knee radiographs and MRI scans obtained at baseline and 30 months later, and plasma phylloquinone (vitamin K) measured at baseline. We examined the relationship of subclinical vitamin K deficiency to incident radiographic knee osteoarthritis and MRI-based cartilage lesions and osteophytes, respectively, using log binomial regression with generalized estimating equations, adjusting for potential confounders. ResultsAmong 1180 participants (62% women, mean age 62±8 years, mean body mass index 30.1±5.1 kg/m2), subclinical vitamin K deficiency was associated with incident radiographic knee osteoarthritis (risk ratio [RR] 1.56; 95% confidence interval [CI], 1.08-2.25) and cartilage lesions (RR 2.39; 95% CI, 1.05-5.40) compared with no deficiency, but not with osteophytes (RR 2.35; 95% CI, 0.54-10.13). Subclinically vitamin K-deficient subjects were more likely to develop osteoarthritis in one or both knees than neither knee (RR 1.33; 95% CI, 1.01-1.75 and RR 2.12; 95% CI, 1.06-4.24, respectively). ConclusionIn the first such longitudinal study, subclinical vitamin K deficiency was associated with increased risk of developing radiographic knee osteoarthritis and MRI-based cartilage lesions. Further study of vitamin K is warranted given its therapeutic/prophylactic potential for osteoarthritis.

Valgus malalignment is a risk factor for lateral knee osteoarthritis incidence and progression: Findings from the multicenter osteoarthritis study and the osteoarthritis initiative

To study the effect of valgus malalignment on knee osteoarthritis (OA) incidence and progression. We measured the mechanical axis from long limb radiographs from the Multicenter Osteoarthritis Study (MOST) and the Osteoarthritis Initiative (OAI) to define limbs with valgus malalignment (mechanical axis of ≥1.1° valgus) and examined the effect of valgus alignment versus neutral alignment (neither varus nor valgus) on OA structural outcomes. Posteroanterior radiographs and knee magnetic resonance (MR) images were obtained at the time of the long limb radiograph and at followup examinations. Lateral progression was defined as an increase in joint space narrowing (on a semiquantitative scale) in knees with OA, and incidence was defined as new lateral narrowing in knees without radiographic OA. We defined lateral cartilage damage and progressive meniscal damage as increases in cartilage or meniscus scores at followup on the Whole-Organ Magnetic Resonance Imaging Score scale (for the MOST) or the Boston Leeds Osteoarthritis Knee Score scale (for the OAI). We used logistic regression with adjustment for age, sex, body mass index, and Kellgren/Lawrence grade, as well as generalized estimating equations, to evaluate the effect of valgus alignment versus neutral alignment on disease outcomes. We calculated odds ratios (ORs) and 95% confidence intervals (95% CIs). We studied 5,053 knees (881 valgus) of subjects in the MOST cohort and 5,953 knees (1,358 valgus) of subjects in the OAI cohort. In both studies, all strata of valgus malalignment, including 1.1° to 3° valgus, were associated with an increased risk of lateral disease progression. In knees without radiographic OA, valgus alignment >3° was associated with incidence (e.g., in the MOST, adjusted OR 2.5 [95% CI 1.0-5.9]). Valgus alignment >3° was also associated with cartilage damage on MR imaging in knees without OA (e.g., in the OAI, adjusted OR 5.9 [95% CI 1.1-30.3]).We found a strong relationship of valgus malalignment with progressive lateral meniscal damage. Valgus malalignment increases the risk of knee OA radiographic progression and incidence as well as the risk of lateral cartilage damage. It may cause these effects, in part, by increasing the risk of meniscal damage.

Peripatellar synovitis: comparison between non-contrast-enhanced and contrast-enhanced MRI and association with pain. The MOST study

To assess the diagnostic performance of signal changes in Hoffa's fat pad (HFP) assessed on non-contrast-enhanced (CE) magnetic resonance imaging (MRI) in detecting synovitis, and the association of pain with signal changes in HFP on non-CE MRI and peripatellar synovial thickness on CE MRI. The Multicenter Osteoarthritis (MOST) Study is an observational study of individuals who have or are at high risk for knee OA. All subjects with available non-CE and CE MRIs were included. Signal changes in HFP were scored from 0 to 3 in two regions using non-CE MRI. Synovial thickness was scored from 0 to 2 on CE MRI in five peripatellar regions. Sensitivity, specificity and accuracy of HFP signal changes were calculated considering synovial thickness on CE MRI as the reference standard. We used logistic regression to assess the associations of HFP changes (non-CE MRI) and synovial thickness (CE MRI) with pain from walking up or down stairs, after adjusting for potential confounders. A total of 393 subjects were included. Sensitivity of infrapatellar and intercondylar signal changes in HFP was high (71% and 88%), but specificity was low (55% and 30%). No significant associations were found between HFP changes on non-CE MRI and pain. Grade 2 synovial thickness assessed on CE MRI was significantly associated with pain after adjustments for potential confounders. Signal changes in HFP detected on non-CE MRI are a sensitive but non-specific surrogate for the assessment of synovitis. CE MRI identifies associations with pain better than non-CE MRI.

Do radiographic disease and pain account for why people with or at high risk of knee osteoarthritis do not meet physical activity guidelines?

Knee osteoarthritis (OA) and pain are assumed to be barriers to meeting physical activity guidelines, but this has not been formally evaluated. The purpose of this study was to determine the proportions of people with and those without knee OA and knee pain who meet recommended physical activity levels through walking. We performed a cross-sectional analysis of community-dwelling adults from the Multicenter Osteoarthritis Study who had or who were at high risk of knee OA. Participants wore a StepWatch activity monitor to record steps per day for 7 days. The proportion of participants who met the recommended physical activity levels was defined as those accumulating≥150 minutes per week at ≥100 steps per minute in bouts lasting ≥10 minutes. These proportions were also determined for those with and those without knee OA, as classified by radiography and by severity of knee pain. Of the 1,788 study participants (mean±SD age 67.2±7.7 years, mean±SD body mass index 30.7±6.0 kg/m2, 60% women), lower overall percentages of participants with radiographic knee OA and knee pain met recommended physical activity levels. However, these differences were not statistically significant between those with and those without knee OA; 7.3% and 10.1% of men (P=0.34) and 6.3% and 7.8% of women (P=0.51), respectively, met recommended physical activity levels. Similarly, for those with moderate/severe knee pain and those with no knee pain, 12.9% and 10.9% of men (P=0.74) and 6.7% and 11.0% of women (P=0.40), respectively, met recommended physical activity levels. Disease and pain have little impact on achieving recommended physical activity levels among people with or at high risk of knee OA.

Body weight changes and corresponding changes in pain and function in persons with symptomatic knee osteoarthritis: A cohort study

To determine if a dose-response relationship exists between percentage changes in body weight in persons with symptomatic knee osteoarthritis (OA) and self-reported pain and function. Data from persons in the Osteoarthritis Initiative (OAI) and the Multicenter Osteoarthritis (MOST) study data sets (n = 1,410) with symptomatic function-limiting knee OA were studied. For the OAI, we used baseline and 3-year followup data, while for the MOST study, baseline and 30-month data were used. Key outcome variables were Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function and pain change scores. In addition to covariates, the predictor variable of interest was the extent of weight change over the study period divided into 5 categories representing different percentages of body weight change. A significant dose-response relationship (P < 0.003) was found between the extent of percentage change in body weight and the extent of change in WOMAC physical function and WOMAC pain scores. For example, persons who gained ≥10% of body weight had WOMAC physical function score changes of -5.4 (95% confidence interval -8.7, -2.00) points, indicating worsening physical function relative to the reference group of persons with weight changes between <5% weight gain and <5% weight reduction. Our data suggest a dose-response relationship exists between changes in body weight and corresponding changes in pain and function. The threshold for this response gradient appears to be body weight shifts of ≥10%. Weight changes of ≥10% have the potential to lead to important changes in pain and function for patient groups as well as individual patients.

The association between meniscal damage of the posterior horns and localized posterior synovitis detected on T1-weighted contrast-enhanced MRI—The MOST study

Synovitis is thought to be a secondary phenomenon in the osteoarthritis (OA) process and the menisci might be triggers of localized synovitis. The aim was to assess the cross-sectional associations of posterior horn meniscal damage with perimeniscal synovitis, and with synovitis posterior to the posterior cruciate ligament (PCL) using contrast enhanced (CE) MRI. The Multicenter Osteoarthritis (MOST) Study is a longitudinal observational study of subjects with or at risk for knee OA. Subjects are a subset of MOST who were examined with 1.5T CE MRI and had semiquantitative synovitis (scored from 0 to 2 at 11 locations) and meniscal readings (scored with WORMS from 0 to 4) available. Logistic regression was used to assess the association of posterior meniscal damage and perimeniscal synovitis in the same compartment, and between posterior meniscal damage and synovitis posterior to the PCL. Three hundred and seventy seven knees were included (mean age 61.1 years±6.9, mean BMI 29.6±4.9, 44.3% women). The odds for ipsi-compartmental perimeniscal synovitis were increased for knees with medial posterior horn meniscal damage (adjusted odds ratio [aOR] 2.5, 95% confidence intervals [95% CI] 1.3,4.8), but not for lateral damage (aOR 1.7, 95% CI 0.4,6.6). No positive associations were found for meniscal damage and presence of synovitis posterior to the PCL (aOR 0.9, 95% CI 0.6,1.5). Meniscal damage of the posterior horns is associated with ipsi-compartmental perimensical synovitis. No associations were found for posterior horn meniscal damage with synovitis posterior to the PCL, which suggests that synovitis posterior to the PCL is likely to be triggered by different pathomechanisms.

Walking to Meet Physical Activity Guidelines in Knee Osteoarthritis: Is 10,000 Steps Enough?

ObjectiveTo study if step goals (eg, walking 10,000 steps a day) approximate meeting the 2008 Physical Activity Guidelines for Americans. DesignCross-sectional observational cohort. SettingCommunity. ParticipantsPeople with or at high risk of knee OA (N=1788). InterventionsNone. Main Outcome MeasuresObjective physical activity data were collected over 7 consecutive days from people with or at high risk of knee OA participating in the Multicenter Osteoarthritis Study. Using activity monitor data, we determined the proportion that (1) walked ≥10,000 steps per day, (2) met the 2008 Physical Activity Guidelines, and (3) achieved both recommendations. ResultsOf the subjects studied (mean age ± SD, 67±8y; mean body mass index ± SD, 31±6kg/m2; 60% women), 16.7% of men and 12.6% of women walked ≥10,000 steps per day, while 6% of men and 5% of women met the 2008 Physical Activity Guidelines for Americans. Of those walking ≥10,000 steps per day, 16.7% and 26.7% of men and women, respectively, also met the 2008 Physical Activity Guidelines. ConclusionsAmong this sample of older adults with or at high risk of knee OA, walking ≥10,000 steps a day did not translate into meeting public health guidelines. These findings highlight the disparity between the number of steps believed to be needed per day and the recommended time-intensity guidelines to achieve positive health benefits.

Prevalent cartilage damage and cartilage loss over time are associated with incident bone marrow lesions in the tibiofemoral compartments: the MOST study

To assess the association of prevalent cartilage damage and cartilage loss over time with incident bone marrow lesions (BMLs) in the same subregion of the tibiofemoral compartments as detected on magnetic resonance imaging (MRI). The Multicenter Osteoarthritis Study is an observational study of individuals with or at risk for knee osteoarthritis (OA). Subjects whose baseline and 30-month follow-up MRIs were read for findings of OA were included. MRI was performed with a 1.0 T extremity system. Tibiofemoral compartments were divided into 10 subregions. Cartilage morphology was scored from 0 to 6 and BMLs were scored from 0 to 3. Prevalent cartilage damage and cartilage loss over time were considered predictors of incident BMLs. Associations were assessed using logistic regression, with adjustments for potential confounders. Medially, incident BMLs were associated with baseline cartilage damage (adjusted odds ratio (OR) 3.9 [95% confidence interval (CI) 3.0, 5.1]), incident cartilage loss (7.3 [95% CI 5.0, 10.7]) and progression of cartilage loss (7.6 [95% CI 5.1, 11.3]) Laterally, incident BMLs were associated with baseline cartilage damage (4.1 [95% CI 2.6, 6.3]), incident cartilage loss (6.0 [95% CI 3.1, 11.8]), and progression of cartilage loss (11.9 [95% CI 6.2, 23.0]). Prevalent cartilage damage and cartilage loss over time are strongly associated with incident BMLs in the same subregion, supporting the significance of the close interrelation of the osteochondral unit in the progression of knee OA.

Co-localisation of non-cartilaginous articular pathology increases risk of cartilage loss in the tibiofemoral joint—the MOST study

PurposeTo assess risk of cartilage loss in the tibiofemoral joint in relation to baseline damage severity, and to analyse the association of nearby pathologic findings on the risk of subsequent...

The longitudinal relationship between thigh muscle mass and the development of knee osteoarthritis

Greater quadriceps strength has been found to reduce risk for symptomatic knee osteoarthritis (SxKOA) and knee joint space narrowing (JSN). However, this finding could relate to muscle mass or activation pattern. The purpose of this study was to assess whether greater thigh muscle mass protects against (1) incident radiographic (RKOA), (2) incident SxKOA or (3) worsening of knee JSN by 30-month follow-up. Multicenter Osteoarthritis (MOST) study participants, who underwent dual-energy X-ray absorptiometry (DXA) at the Iowa site were included. Thigh muscle mass was calculated from DXA image sub-regions. Sex-stratified, knee-based analyses controlled for incomplete independence between limbs within subjects. The effect of thigh lean mass and specific strength as predictors of ipsilateral RKOA, SxKOA and worsening of JSN were assessed, while controlling for age, body mass index (BMI), and history of knee surgery. A total of 519 men (948 knees) and 784 women (1453 knees) were included. Mean age and BMI were 62 years and 30kg/m(2). Thigh muscle mass was not associated with risk for RKOA, SxKOA or knee JSN. However, in comparison with the lowest tertile, those in the highest and middle tertiles of knee extensor specific strength had a lower risk for SxKOA and JSN [odds ratio (OR) 0.29-0.68]. Thigh muscle mass does not appear to confer protection against incident or worsening knee OA. These findings suggest that future studies of risk for knee OA should focus on the roles of knee extensor neuromuscular activation and muscle physiology, rather than the muscle mass.

When it hurts, a positive attitude may help: association of positive affect with daily walking in knee osteoarthritis. Results from a multicenter longitudinal cohort study

While depressive symptoms and knee pain are independently known to impede daily walking in older adults, it is unknown whether positive affect promotes daily walking. This study investigated this association among adults with knee osteoarthritis (OA) and examined whether knee pain modified this association. This study is a cross-sectional analysis of the Multicenter Osteoarthritis Study. We included 1,018 participants (mean ± SD age 63.1 ± 7.8 years, 60% women) who had radiographic knee OA and had worn a StepWatch monitor to record their number of steps per day. High and low positive affect and depressive symptoms were based on the Center for Epidemiologic Studies Depression Scale. Knee pain was categorized as present in respondents who reported pain on most days at both a clinic visit and a telephone screening. Compared to respondents with low positive affect (27% of all respondents), those with high positive affect (63%) walked a similar number of steps per day, while those with depressive symptoms (10%) walked less (adjusted β -32.6 [95% confidence interval (95% CI) -458.9, 393.8] and -579.1 [95% CI -1,274.9, 116.7], respectively). There was a statistically significant interaction of positive affect by knee pain (P = 0.0045). Among the respondents with knee pain (39%), those with high positive affect walked significantly more steps per day (adjusted β 711.0 [95% CI 55.1, 1,366.9]) than those with low positive affect. High positive affect was associated with more daily walking among adults with painful knee OA. Positive affect may be an important psychological factor to consider for promoting physical activity among people with painful knee OA.

Knee malalignment is associated with an increased risk for incident and enlarging bone marrow lesions in the more loaded compartments: the MOST study

To examine the relationship of knee malalignment with occurrence of incident and enlarging bone marrow lesions (BMLs) and regression of BMLs. Subjects from the Multicenter Osteoarthritis Study aged 50-79 years with or at high risk of knee osteoarthritis were studied. Full-limb radiographs were taken at baseline and hip-knee-ankle mechanical axis was measured. Baseline and 30-month magnetic resonance imaging (MRI) of knees (n=1782) were semiquantitatively assessed for BMLs. Outcome was defined as a change in BML score in femoral/tibial condyle in medial/lateral compartments. Medial compartment in varus alignment and lateral compartment in valgus alignment were combined to form 'more loaded' compartment, while lateral compartment in valgus and medial compartment in varus were combined to form 'less loaded' compartment. Relative risk (RR) of BML score increase or decrease in relation to malalignment was estimated using a log linear regression model with the Poisson assumption, adjusting for age, gender, body mass index, physical activity scale for the elderly, race and clinic site. Further, results were stratified by ipsilateral meniscal and cartilage status at baseline. Baseline varus alignment was associated with higher risk of BML score increase from baseline to follow-up in the medial compartment [adjusted RRs (95%CI): 1.5 (1.2-1.9)] and valgus alignment in the lateral compartment [1.4 (1.0-2.1)]. Increase in BML score was more likely in the more loaded compartments [1.7 (1.4-2.0)] in malaligned knees. Regardless of ipsilateral cartilage or meniscus status, adjusted RR for BML score increase was higher in the more loaded compartments of malaligned knees than those with neutral alignment. Decrease in BML score was less likely in the more loaded compartments in malaligned knees [0.8 (0.7-1.0)]. Knee malalignment is associated with increased risk of incident and enlarging BMLs in the more loaded compartments of the tibiofemoral joint.

Predictive validity of within-grade scoring of longitudinal changes of MRI-based cartilage morphology and bone marrow lesion assessment in the tibio-femoral joint – the MOST study

In order to increase sensitivity to detect longitudinal change, recording of within-grade changes was introduced for cartilage morphology and bone marrow lesion (BML) assessment in semiquantitative magnetic resonance imaging (MRI) scoring of knee osteoarthritis (OA). The aim of this study was to examine the validity provided by within-grade scoring. The Multicenter Osteoarthritis (MOST) study is a longitudinal study of subjects with or at risk of knee OA. Baseline and 30 months MRIs were read according to the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS) system including within-grade changes for cartilage and BMLs. We tested the validity of within-grade changes by whether the 30-month changes in cartilage and BML assessment were predicted by baseline ipsi-compartmental meniscal damage and malalignment, factors known to affect cartilage loss and BMLs, using ordinal logistic regression. 1867 Knees (from 1411 participants) were included. Severe medial meniscal damage predicted partial grade (adjusted odds ratio (aOR) 4.4, 95% confidence interval (95% CI) 2.2, 8.7) but not ≥full grade (aOR 1.3, 95% CI 0.8, 2.2) worsening of cartilage loss and predicted both, partial grade (aOR 9.6, 95% CI 3.6, 25.1) and ≥full grade (aOR 5.1, 95% CI 3.2, 8.2) worsening of BMLs. Severe, but not moderate, malalignment predicted ipsi-compartmental within-grade (medial cartilage damage: aOR 5.5, 95% CI 2.6, 11.6; medial worsening of BMLs: aOR 4.9, 95% CI 2.0, 12.3) but not full grade worsening of BMLs and cartilage damage. Within-grade changes in semiquantitative MRI assessment of cartilage and BMLs are valid and their use may increase the sensitivity of semiquantitative readings in detecting longitudinal changes in these structures.

Factors Associated with Meniscal Extrusion in Knees with or at Risk for Osteoarthritis: The Multicenter Osteoarthritis Study

To assess the associations of meniscal tears, knee mal-alignment, cartilage damage, knee effusion, and body mass index with meniscal extrusion. The Multicenter Osteoarthritis study is an observational study of individuals who have or are at risk for knee osteoarthritis (OA). The HIPAA-compliant protocol was approved by the institutional review boards of all participating centers, and written informed consent was obtained from all patients. All subjects with available baseline knee radiographs and magnetic resonance (MR) images were included. MR imaging assessment of meniscal morphologic characteristics, meniscal position, and cartilage morphologic characteristics with use of the Whole-Organ Magnetic Resonance Imaging Score system was performed by two musculoskeletal radiologists. Cross-sectional associations of severity of meniscal tears, knee malalignment, tibiofemoral cartilage damage, knee effusion, and body mass index with meniscal extrusion were assessed by using logistic regression, with multiadjustments when testing each predictor. A total of 1527 subjects (2131 knees; 2116 medial and 2106 lateral menisci) were included. Medially, meniscal tears, varus malalignment, and cartilage damage were associated with meniscal extrusion, with odds ratios (ORs) of 6.3 (95% confidence interval [CI]: 5.0, 8.0), 1.3 (95% CI: 1.1, 1.7), and 1.8 (95% CI: 1.4, 2.2), respectively. Laterally, meniscal tears, valgus malalignment, and cartilage damage were associated with meniscal extrusion, with ORs of 10.3 (95% CI: 7.1, 14.9), 2.2 (95% CI: 1.5, 3.2), and 2.0 (95% CI: 1.3, 2.9), respectively. Meniscal tears are not the only factors associated with meniscal extrusion; other factors include knee malalignment and cartilage damage. Meniscal extrusion is probably an effect of the complex interactions among joint tissues and mechanical stresses involved in the OA process.