Progression of osteoarthritis as a state of inertia.

OBJECTIVES: To test whether knees which recently developed disease were at higher risk for subsequent x-ray progression than knees which had been stable, suggesting that recent change produces further change and recent stability yields subsequent stability (a pattern of inertia). METHODS: We used central readings of the annual posteroanterior x-rays obtained in the Osteoarthritis Initiative (OAI) focusing on change in Kellgren and Lawrence (KL) grade and change in semiquantitative joint space. We examined whether knees that had developed incident disease (KL grade 2) were at higher risk of subsequent progression than knees that were already grade 2 and had had stable disease. We combined data from multiple examinations. Using generalised estimating equations to adjust for the correlation between knees, we carried out logistic regression evaluating the risk for disease progression testing incident versus stable disease adjusting for age, sex, body mass index, physical activity, quadriceps strength and mechanical alignment. RESULTS: 1562 OAI subjects with grade 2 disease had a mean age of 61.8 years, mean BMI of 29.4, and 61.7% were women. Of knees with stable disease, 4.1% showed progression within the next 12 months in KL grade versus 13.7% in those with incident disease (adjusted OR 4.0; 95% CI 2.4 to 6.7). For progression of joint space loss, we found a similar relation with incident versus stable disease (adjusted OR 5.3; 95% CI 3.6 to 7.9). CONCLUSIONS: Knee osteoarthritis radiographic progression follows a pattern of inertia. Factors that trigger the transition from stable disease to progression should be sought.

Meniscal tear in knees without surgery and the development of radiographic osteoarthritis among middle-aged and elderly persons: The Multicenter Osteoarthritis Study.

OBJECTIVE: Although partial meniscectomy is a risk factor for the development of knee osteoarthritis (OA), there is a lack of evidence that meniscal damage that is not treated with surgery would also lead to OA, suggesting that surgery itself may cause joint damage. Furthermore, meniscal damage is common. The aim of this study was to evaluate the association between meniscal damage in knees without surgery and the development of radiographic tibiofemoral OA. METHODS: We conducted a prospective case-control study nested within the observational Multicenter Osteoarthritis Study, which included a sample of men and women ages 50-79 years at high risk of knee OA who were recruited from the community. Patients who had no baseline radiographic knee OA but in whom tibiofemoral OA developed during the 30-month followup period were cases (n = 121). Control subjects (n = 294) were drawn randomly from the same source population as cases but had no knee OA after 30 months of followup. Individuals whose knees had previously undergone surgery were excluded. Meniscal damage was defined as the presence of any medial or lateral meniscal tearing, maceration, or destruction. RESULTS: Meniscal damage at baseline was more common in case knees than in control knees (54% versus 18%; P < 0.001). The model comparing any meniscal damage with no meniscal damage (adjusted for baseline age, sex, body mass index, physical activity, and mechanical knee alignment) yielded an odds ratio of 5.7 (95% confidence interval 3.4-9.4). CONCLUSION: In knees without surgery, meniscal damage is a potent risk factor for the development of radiographic OA. These results highlight the need for better understanding, prevention, and treatment of meniscal damage.

A new approach yields high rates of radiographic progression in knee osteoarthritis.

OBJECTIVE: Progression of knee osteoarthritis (OA) has typically been assessed in the medial tibiofemoral (TF) compartment on the anteroposterior (AP) or posteroanterior (PA) view. We propose a new approach using multiple views and compartments that is likely to be more sensitive to change and reveals progression throughout the knee. METHODS: We tested our approach in the Multicenter Osteoarthritis Study, a study of persons with OA or at high risk of disease. At baseline and 30 months, subjects provided PA (fixed flexion without fluoro) and lateral weight-bearing knee radiographs. Paired radiographs were read by 2 readers who scored joint space (JS) using a 0-3 atlas-based scale. When JS narrowed but narrowing did not reach a full grade on the scale, readers used half-grades. Change was scored in medial and lateral TF compartments on both PA and lateral views and in the patellofemoral (PF) joint on lateral view. A knee showed progression when there was at least a half-grade worsening in JS width in any compartment at followup. Disagreements were adjudicated by a panel of 3 readers. To validate progression, we tested definitions for TF progression to see if malalignment on long-limb radiographs at baseline (>or=3 degrees malaligned in any direction with nonmalaligned knees being reference) increased risk of progression. A valid definition of progression would show that malalignment strongly predicted progression. RESULTS: We studied 842 knees with either Kellgren-Lawrence grade>or=2 or PF OA at baseline in 606 subjects (age range 50-79 yrs, mean 63.9 yrs; 66.6% women). Mean body mass index was 31.9, and 32.8% of knees had frequent knee pain at baseline. Of these, 500 knees (59.4%) showed progression. Of the 500, 75 (15%) had progression only in the PF joint, while the remainder had progression in the TF joint. Malalignment increased the risk of overall progression in TF joint and increased the risk of half-grade progression, suggesting that half-grade progression had validity. CONCLUSION: PA and lateral views obtained in persons at high risk of OA progression can produce a cumulative incidence of progression above 50% at 30 months. Keys to increasing the yield include imaging PF and lateral compartments, using semiquantitative scales designed to detect change, and examining more than one radiographic view.

Knee buckling: prevalence, risk factors, and associated limitations in function.

BACKGROUND: Knee buckling is common in persons with advanced knee osteoarthritis and after orthopedic procedures. Its prevalence in the community is unknown. OBJECTIVE: To examine the prevalence of knee buckling in the community, its associated risk factors, and its relation to functional limitation. DESIGN: Cross-sectional, population-based study. SETTING: The Framingham Osteoarthritis Study. PARTICIPANTS: 2351 men and women age 36 to 94 years (median, 63.5 years). MEASUREMENTS: Participants were asked whether they had experienced knee buckling or "giving way" and whether it led to falling. They were also asked about knee pain and limitations in function by using the Short Form-12 and Western Ontario and McMaster Universities Osteoarthritis Index, had isometric tests of quadriceps strength, and underwent weight-bearing radiography and magnetic resonance imaging of the knee. Radiographs were scored for osteoarthritis by using the Kellgren-Lawrence scale, and magnetic resonance images were read for anterior cruciate ligament tears. The relationship of buckling to functional limitation was examined by using logistic regression that adjusted for age, sex, body mass index, and knee pain severity. RESULTS: Two hundred seventy-eight participants (11.8%) experienced at least 1 episode of knee buckling within the past 3 months; of these persons, 217 (78.1%) experienced more than 1 episode and 35 (12.6%) fell during an episode. Buckling was independently associated with the presence of knee pain and with quadriceps weakness. Over half of those with buckling had no osteoarthritis on radiography. Persons with knee buckling had worse physical function than those without buckling, even after adjustment for severity of knee pain and weakness. For example, 46.9% of participants with buckling and 21.7% of those without buckling reported limitations in their work (adjusted odds ratio, 2.0 [95% CI, 1.5 to 2.7]). LIMITATION: Causal inferences are limited because of the study's cross-sectional design. CONCLUSION: In adults, knee buckling is common and is associated with functional loss.

Knee alignment does not predict incident osteoarthritis: the Framingham osteoarthritis study.

OBJECTIVE: To examine the relationship of knee malalignment to the occurrence of knee osteoarthritis (OA) among subjects without radiographic OA at baseline to determine whether malalignment is a risk factor for incident disease or simply a marker of increasing disease severity. METHODS: We selected 110 incident tibiofemoral (TF) OA case knees (76 subjects) and 356 random control knees (178 subjects) from among participants in the Framingham Osteoarthritis Study. Case knees did not have OA at baseline (1992-1994 examination) but had developed OA (Kellgren/Lawrence grade>or=2) at followup (2002-2005 examination) (mean of 8.75 years between examinations). Control knees did not have OA at baseline. Standardized digital radiographs of the fully extended knee with weight-bearing were read using a standard protocol and eFilm viewing software. We measured the anatomic axis, the condylar angle, the tibial plateau angle, and the condylar tibial plateau angle. The interobserver intraclass correlation coefficient (ICC) ranged from 0.93 to 0.96 and the intraobserver ICC from 0.94 to 0.97. In a knee-specific analysis, we examined the relationship of each alignment measurement to the risk of TF OA using generalized estimating equations, adjusting for age, sex, and body mass index (BMI). We used the same approach to assess the association between each alignment measurement and the risk of medial TF OA. RESULTS: Subjects in the case population were older and had a higher BMI than the controls. The alignment values were normally distributed and were not different between the cases and the controls. After adjustment for age, sex and BMI, there was no significant increase in incident OA in the highest quartile compared with the lowest quartile category for any of the alignment measures (P for trend for anatomic axis and condylar tibial plateau angle was 0.83 and 0.80, respectively). Similar results were also observed for medial compartment OA. CONCLUSION: We found that baseline knee alignment is not associated with either incident radiographic TF OA or medial TF OA. These results suggest that malalignment is not a risk factor for OA, but rather is a marker of disease severity and/or its progression.

Effect of recreational physical activities on the development of knee osteoarthritis in older adults of different weights: the Framingham Study.

OBJECTIVE: To evaluate the long-term effect of recreational exercise on the development of knee osteoarthritis (OA) in a community-based cohort of older adults, many of whom were overweight or obese. METHODS: Subjects were asked about recreational activities including walking or jogging for exercise and working up a sweat, and were asked to compare their activity levels with others. Subjects were then asked about knee pain and weight-bearing anteroposterior and lateral knee radiographs were obtained. Approximately 9 years later, subjects were reexamined for OA. Radiographs were read for OA features in both tibiofemoral and patellofemoral compartments and were scored for tibiofemoral joint space narrowing. To evaluate incident OA, we excluded knees with OA at baseline for all analyses and focused on 3 knee-specific outcomes: incident radiographic OA, symptomatic OA, and tibiofemoral joint space loss. After adjusting for age, sex, body mass index (BMI), knee injury history, and correlation between knees, we evaluated the association of each recreational activity with OA development. RESULTS: A total of 1,279 subjects underwent both baseline and followup examinations (mean age at baseline 53.2 years). Neither recreational walking, jogging, frequent working up a sweat, nor high activity levels relative to peers were associated with a decrease or increase in risk of OA. Joint space loss was also unaffected by activity. Persons with BMI above the median (27.7 kg/m(2) for men and 25.7 kg/m(2) for women; mean BMI >30 kg/m(2) for both) had no increases in risk of OA by different type of activity. CONCLUSION: Among middle-aged and elderly persons without knee OA, many of whom were overweight, recreational exercise neither protects against nor increases risk of knee OA.

Low levels of vitamin D and worsening of knee osteoarthritis: results of two longitudinal studies.

OBJECTIVE: To confirm reports that 25-hydroxyvitamin D (25[OH]D) deficiency is associated with an increased risk of joint space narrowing or cartilage loss in osteoarthritis (OA). METHODS: We measured 25(OH)D levels in subjects from 2 longitudinal cohort studies, the Framingham Osteoarthritis Study and the Boston Osteoarthritis of the Knee Study (BOKS). In the first, weight-bearing anteroposterior (AP) and lateral knee radiographs were obtained on subjects in 1993-1994 and again in 2002-2005 (mean interval 9 years); blood was drawn for measurement of vitamin D status in 1996-2000. In the second, subjects with symptomatic knee OA participating in a natural history study had fluoroscopically positioned semiflexed posteroanterior (PA) and lateral radiography of both knees and magnetic resonance imaging (MRI) of the more symptomatic knee performed at baseline and at 15 and 30 months. Blood was drawn at all visits, and the baseline specimen was used when available. In both studies, we defined radiographic worsening based on joint space loss in the tibiofemoral joint on either AP/PA or lateral weight-bearing views, using a semiquantitative scale (worsening defined as increase by > or =1 on a 0-3 scale). In the BOKS, we evaluated cartilage loss semiquantitatively, using the Whole-Organ Magnetic Resonance Imaging Score. In both studies, 25(OH)D levels were measured by radioimmunoassay. Analyses focused on whether vitamin D levels, defined in tertiles or as deficient (25[OH]D <20 ng/ml) versus nondeficient, predicted worsening of OA. Logistic regression analysis adjusted for age, body mass index, sex, and baseline OA level was used. RESULTS: The 715 subjects in the Framingham Study had a mean 25(OH)D level of 20 ng/ml at baseline, and 20.3% of the knees showed worsening, during the course of the study, with most knees having had no evidence of OA at baseline. The 277 subjects with OA in the BOKS had a mean 25(OH)D level of 20 ng/ml at baseline with 23.6% of knees showing radiographic worsening. We found no association of baseline 25(OH)D levels with radiographic worsening in either cohort, and confidence limits in the analyses of vitamin D deficiency were narrow, suggesting that results were not based on insufficient power. In fact, the risk of worsening was slightly, but not significantly, lower in persons with low levels of vitamin D than in persons with higher levels. In the BOKS, vitamin D levels were unrelated to cartilage loss seen on MRI. CONCLUSION: The findings indicate that vitamin D status is unrelated to the risk of joint space or cartilage loss in knee OA.