Increase in vastus medialis cross-sectional area is associated with reduced pain, cartilage loss, and joint replacement risk in knee osteoarthritis.

OBJECTIVE: Although there is evidence for a beneficial effect of increased quadriceps strength on knee symptoms, the effect on knee structure is unclear. We undertook this study to examine the relationship between change in vastus medialis cross-sectional area (CSA) and knee pain, tibial cartilage volume, and risk of knee replacement in subjects with symptomatic knee osteoarthritis (OA). METHODS: One hundred seventeen subjects with symptomatic knee OA underwent magnetic resonance imaging of the knee at baseline and at 2 and 4.5 years. Vastus medialis CSA was measured at baseline and at 2 years. Tibial cartilage volume was measured at baseline and at 2 and 4.5 years. Knee pain was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index at baseline and at 2 years. The frequency of knee joint replacement over 4 years was determined. Regression coefficients (B) and odds ratios were determined along with 95% confidence intervals (95% CIs). RESULTS: After adjusting for confounders, baseline vastus medialis CSA was inversely associated with current knee pain (r = -0.16, P = 0.04) and with medial tibial cartilage volume loss from baseline to 2 years (B coefficient -10.9 [95% CI -19.5, -2.3]), but not with baseline tibial cartilage volume. In addition, an increase in vastus medialis CSA from baseline to 2 years was associated with reduced knee pain over the same time period (r = 0.24, P = 0.007), reduced medial tibial cartilage loss from 2 to 4.5 years (B coefficient -16.8 [95% CI -28.9, -4.6]), and reduced risk of knee replacement over 4 years (odds ratio 0.61 [95% CI 0.40, 0.94]). CONCLUSION: In a population of patients with symptomatic knee OA, increased vastus medialis size was associated with reduced knee pain and beneficial structural changes at the knee, suggesting that management of knee pain and optimizing vastus medialis size are important in reducing OA progression and subsequent knee replacement.

Temporal relationship between serum adipokines, biomarkers of bone and cartilage turnover, and cartilage volume loss in a population with clinical knee osteoarthritis.

OBJECTIVE: The association of obesity with both hand and knee osteoarthritis (OA) is suggestive of a link between dysfunctional metabolism and joint integrity. Given the role of adipokines in mediating bone and cartilage homeostasis, we undertook this study to examine the relationship between adipokines and bone and cartilage biomarkers in a population of subjects with OA, and to determine whether adipokine levels predicted 2-year cartilage integrity. METHODS: One hundred seventeen subjects underwent magnetic resonance imaging at baseline and at 2-year followup. Cartilage volume was assessed from these images. Serum adipokine levels were measured at baseline. Bone and cartilage biomarker levels were measured at baseline and at 2-year followup. Linear regression was used to examine the relationship between baseline levels of adipokines and adipokine receptors (leptin, soluble leptin receptor [sOB-Rb], resistin, and adiponectin) and changes in levels of bone biomarkers (osteocalcin, N-terminal type I procollagen propeptide [PINP], C-terminal crosslinking telopeptide of type I collagen, N-terminal crosslinking telopeptide of type I collagen, or C-terminal crosslinking telopeptide of type I collagen generated by matrix metalloproteinases), levels of cartilage biomarkers (cartilage oligomeric matrix protein, N-terminal type IIA procollagen propeptide [PIIANP], or C2C), cartilage defects score, and cartilage volume over 2 years. RESULTS: Baseline leptin was associated with increased levels of bone formation biomarkers (osteocalcin and PINP) over 2 years, while sOB-Rb was associated with reduced levels of osteocalcin. Baseline sOB-Rb was associated with reduced levels of the cartilage formation biomarker PIIANP, an increased cartilage defects score, and increased cartilage volume loss over 2 years. All results were independent of age, sex, and body mass index. CONCLUSION: The findings of this study support the concept that serum adipokines may provide a nonmechanical link between obesity and joint integrity (which may be mediated by bone and cartilage turnover) that subsequently results in changes to the cartilage defects score and cartilage volume loss. This may facilitate our understanding of the mechanisms by which obesity is involved in the pathogenesis of OA.

Sex differences in the relationship between bone mineral density and tibial cartilage volume.

OBJECTIVE: Although there is a well-established sex difference in the prevalence and severity of OA, the mechanism for this is not clear. The aim of this study was to examine the potential role of BMD and BMC in explaining gender differences in knee cartilage volume. METHODS: A total of 153 subjects aged 25-60 years, 81% female, were recruited. MRI was performed of the dominant knee. Cartilage volume was measured using validated methods. Total body BMD and content was measured using DXA. RESULTS: Total body BMC and BMD was significantly associated with medial cartilage volume in both sexes. However, the associations were stronger in men for BMC (B = 0.52; 95% CI 0.21, 0.83; P for difference = 0.001) and BMD (B = 2242; 95% CI 443, 4041; P for difference = 0.05). Similar results were obtained in the lateral tibial compartment. No significant association was obtained between total body BMD and BMC and patella cartilage volume in either men or women. CONCLUSIONS: In this relatively healthy population, we found a positive relationship between total body BMD and BMC and tibial cartilage volume in the medial and lateral compartments. These relationships were stronger in men than women. Thus, the results of this study may provide some insight into the sex differences in knee cartilage volume, which may in turn facilitate our understanding of the pathogenesis of OA.

Relationship of serum markers of cartilage metabolism to imaging and clinical outcome measures of knee joint structure.

BACKGROUND: Biomarkers of cartilage metabolism have prognostic potential. OBJECTIVE: To examine whether serum cartilage biomarkers, cartilage oligomeric matrix protein (COMP), N-propeptide of type IIA procollagen (PIIANP), type II collagen breakdown product (collagen type-II cleavage (C2C)) predict cartilage volume loss and knee joint replacement. METHODS: 117 subjects with knee osteoarthritis (OA) had MRI at baseline and 2 years. Cartilage biomarkers were measured at baseline. Change in knee cartilage volume over 2 years and knee joint replacement over 4 years was determined. The population was divided into subgroups with high or low cartilage biomarkers (based on biomarker levels greater than or equal to, or less than, the mean, respectively). The relationships between biomarkers and outcome measures were examined in the whole population, and separately in marker subgroups. RESULTS: The relationship between cartilage biomarkers and cartilage volume loss was not linear across the whole population. In the low (regression coefficient B=-9.7, 95% CI -0.01 to 0.003, p=0.01), but not high (B=-0.46, 95% CI -8.9 to 8.0, p=0.92) COMP subgroup, COMP was significantly associated with a reduced rate of medial cartilage volume loss (p for difference between groups=0.05). Similarly, in the low (B=-8.2, 95% CI -12.9 to -3.5, p=0.001) but not high (B=2.6, 95% CI -3.3 to 8.5, p=0.38) PIIANP subgroup, PIIANP was associated with a significantly reduced rate of medial volume cartilage loss (p for difference=0.003). C2C was not significantly associated with rate of cartilage volume loss. PIIANP was associated with a reduced risk of joint replacement (odds ratio (OR)=0.28, 95% CI 0.10 to 0.93, p=0.04). CONCLUSION: Cartilage biomarkers may be used to identify subgroups among those with clinical knee OA in whom disease progresses at different rates. This may facilitate our understanding of the pathogenesis of disease and allow us to differentiate phenotypes of disease within a heterogeneous knee OA population.

Bone marrow lesions in people with knee osteoarthritis predict progression of disease and joint replacement: a longitudinal study.

OBJECTIVES: The presence of bone marrow lesions (BMLs) has been linked to pain and progression of knee OA. The aim of this study was to determine the relationship between BMLs and longitudinal change in tibial cartilage volume and risk of knee joint replacement in subjects with knee OA. METHODS: One hundred and nine men and women with symptomatic knee OA were recruited. The same knee was imaged using MRI at baseline and ∼2 years later. Tibial cartilage volume and BMLs were measured. Knee joint replacement over 4 years was determined. RESULTS: The mean age of the subjects at baseline was 63.2 (s.d. 10.3) years. BMLs were present in 66% of the subjects. Cross-sectionally, BMLs were negatively associated with both medial (regression coefficient -121.4; 95% CI -183.8, -859.1; P<0.001) and lateral (regression coefficient -142.1; 95% CI -241.8, -42.4; P=0.01) tibial cartilage volume data. Longitudinally, for every 1-score increase in baseline BML severity (range 0-4), the annual total tibial cartilage loss was increased by 1.14% (95% CI 0.29%, 1.87%; P=0.01). The risk of knee joint replacement over 4 years increased with increasing BML score (odds ratio 1.57; 95% CI 1.04, 2.35; P=0.03). CONCLUSION: The prevalence and severity of BMLs are associated with less tibial cartilage volume and greater cartilage loss over 2 years. Moreover, severity of BMLs was positively associated with risk of knee joint replacement over 4 years. This provides further support for the importance of BMLs in identifying those with OA most likely to progress. Identifying factors that prevent or reduce the severity of BMLs may provide an important target in the prevention of disease progression and treatment of OA, and the subsequent need for arthroplasty.

The relationship between body composition and structural changes at the knee.

OBJECTIVE: Obesity is an important risk factor for knee OA. Evidence suggests that fat and muscle have differential effects on the pathogenesis of disease. The aim of this study was to examine the relationship between body composition and knee structure, including knee cartilage volume, defects and bone marrow lesions (BMLs). METHODS: A total of 153 subjects aged 25-60 years, 81% females, were recruited across a range of BMI (18-55 kg/m2) for a study examining the relationship between obesity and musculoskeletal disease. MRI was performed of the dominant knee. Cartilage volume, defects and BMLs were measured using validated methods. Body composition was measured using dual X-ray absorptiometry. RESULTS: There was an 81 (95% CI: 69, 94) mm3 increase in cartilage volume for every 1 kg increase in skeletal muscle mass. Fat mass was not significantly associated with cartilage volume. Fat mass, but not skeletal muscle mass, was a risk factor for cartilage defects and BMLs. For every 1 kg increase in total body fat there was an increased risk of cartilage defects (OR=1.31, 95% CI: 1.04, 1.64) and BMLs (OR=1.09, 95% CI: 1.01, 1.18). CONCLUSIONS: In this relatively healthy population, fat mass was associated with increased cartilage defects and BMLs, which are features of early knee OA. In contrast, skeletal muscle mass was positively associated with cartilage volume, which may be due to coinheritance, a commonality of environmental factors associated with cartilage accrual or a protective effect of increased muscle.

Increased fasting serum glucose concentration is associated with adverse knee structural changes in adults with no knee symptoms and diabetes.

OBJECTIVE: There is evidence to suggest that elevated glucose concentration and clinical diabetes are associated with osteoarthritis (OA). However, the association may be confounded by knee symptoms, concomitant treatment for OA or diabetes. We performed a longitudinal cohort study to examine the relationship between serum glucose concentration and knee structure in adults with no knee symptoms or diabetes. METHODS: 179 participants who had fasting serum glucose measurements at 1990-4, with no knee symptoms or diabetes (physician-diagnosed or fasting serum glucose ≥7 mmol/L), underwent knee MRI in 2003-4 and 2 years later. Body mass index was measured at 1990-4 and 2003-4. Cartilage volume and bone marrow lesions were determined from MRI at 2003-4 and 2006-7. RESULTS: Fasting serum glucose concentration was positively associated with the rate of tibial cartilage volume loss over 2 years in women (B=44.2mm(3), 95% CI 4.6, 83.8) but not in men (B=6.0mm(3), 95% CI -68.5, 80.6). Fasting serum glucose concentration was positively associated with incident bone marrow lesions in women (OR=5.76, 95% CI 1.06, 31.21) but not in men (OR=0.11, 95% CI 0.01, 1.79) with significant gender difference (p=0.001 for interaction). CONCLUSION: Increased fasting serum glucose concentration in a non-diabetic population was associated with adverse structural changes at the knee in women but not in men, suggesting that there may be susceptibility to knee structural change even below the arbitrary "diabetic range" of serum glucose levels. The sex differences warrant further investigation as this may be one mechanism underlying the sex difference in knee OA.

Markers of bone formation and resorption identify subgroups of patients with clinical knee osteoarthritis who have reduced rates of cartilage loss.

OBJECTIVE: To determine whether serum markers of bone formation and resorption, used individually or in combination, can be used to identify subgroups who lose cartilage volume at different rates over 2 years within a knee osteoarthritis (OA) population. METHODS: Changes in cartilage volume over 2 years were measured in 117 subjects with knee OA using magnetic resonance imaging. We examined relationships between change in cartilage volume and baseline serum markers of bone formation [intact N-terminal propeptide of type I procollagen (PINP) and osteocalcin] and resorption [N-telopeptide of type I collagen (NTX-I), C-telopeptide of type I collagen (CTX-I), and C-telopeptide of type I collagen (ICTP). RESULTS: The baseline markers of bone formation, PINP and osteocalcin (p = 0.02, p = 0.01, respectively), and the baseline markers of bone resorption, CTX-I and NTX-I (p = 0.02 for both), were significantly associated with reduced cartilage loss. There were no significant associations between baseline ratios of bone formation to resorption markers and cartilage loss. However, when subjects were divided into subgroups with high or low bone formation markers (based on levels of marker >or= mean or < mean for the population, respectively), in the subgroup with high PINP there was a significant association between increasing bone resorption markers CTX-I and NTX-I and reduced cartilage loss (p = 0.02, p = 0.001, respectively). Similarly, in the subgroup with high osteocalcin, there was a significant association between increasing CTX-I and NTX-I and reduced cartilage loss (p = 0.02, p = 0.003, respectively). In contrast, in subgroups with low bone formation markers, no significant associations were obtained between markers of bone resorption and cartilage loss. CONCLUSION: Overall, the results suggest that higher bone remodeling (i.e., higher serum levels of bone formation and resorption) is associated with reduced cartilage loss. Considering markers of bone formation and resorption together, it is possible to identify subgroups within the OA population who have reduced rates of cartilage loss.

Occupational activity is associated with knee cartilage morphology in females.

INTRODUCTION: Knee osteoarthritis (OA) is a major cause of pain and disability in women, becoming a major health problem in mid to later life. A better understanding of factors contributing to deleterious structural knee changes may be important for preventing OA. In men, occupations associated with frequent knee bending have been shown to be associated with damage to knee cartilage. This has not been examined in women. The aim of this study was to examine the effect of occupational specific knee activities on tibial and patella cartilage morphology among healthy females. METHODS: 96 females aged 26-62 years with no history of knee injury or symptoms were recruited as part of a study of community-based study of lifestyle factors on knee health. Occupational activity data examining the frequency of tasks such as heavy lifting, knee bending, stair climbing, walking and standing were obtained by questionnaire. Tibial and patella cartilage volumes and defects were measured from magnetic resonance imaging using validated methods. RESULTS: Heavy lifting/bending/squatting, knee bending, stair climbing and walking were all associated with an increased risk of patella, but not tibial, cartilage defects (odds ratio 1.8-2.9; p

The natural history of bone marrow lesions in community-based middle-aged women without clinical knee osteoarthritis.

OBJECTIVE: Bone marrow lesions (BML) have been implicated in the pathogenesis of osteoarthritis, yet their exact role, etiology, and natural history remain unclear. The aim of this study was to examine the natural history of BML in a healthy population and identify risk factors associated with their persistence and incidence. METHODS: One hundred forty-eight healthy middle-aged women had magnetic resonance imaging performed on their dominant knee at baseline and 2 years later to assess the presence, natural history, and risk factors for persistence and incidence of BML. RESULTS: Approximately 46% of BML present at baseline completely resolved over 2 years. "Large" BML had the potential to improve, while the majority of "very large" remained stable. In those women with no BML at baseline, approximately 9% developed a BML over 2 years, the majority in the medial compartment. There was a trend toward weight being a risk factor for the development of "very large" BML (P = 0.08). CONCLUSIONS: The natural history of BML may be different in healthy persons compared with diseased states. The trend for weight as a risk factor for development of a "very-large" BML suggests there is potential to identify modifiable risk factors for BML in asymptomatic people and warrants further investigation.

Vastus medialis cross-sectional area is positively associated with patella cartilage and bone volumes in a pain-free community-based population.

INTRODUCTION: Although vastus medialis and lateralis are important determinants of patellofemoral joint function, their relationship with patellofemoral joint structure is unknown. The aim of this study was to examine potential determinants of vastus medialis and lateralis cross-sectional areas and the relationship between the cross-sectional area and patella cartilage and bone volumes. METHODS: Two hundred ninety-seven healthy adult subjects had magnetic resonance imaging of their dominant knee. Vastus medialis and lateralis cross-sectional areas were measured 37.5 mm superior to the quadriceps tendon insertion at the proximal pole of the patella. Patella cartilage and bone volumes were measured from these images. Demographic data and participation in vigorous physical activity were assessed by questionnaire. RESULTS: The determinants of increased vastus medialis and lateralis cross-sectional areas were older age (P