Anita E. Wluka

Meniscal extrusion predicts increases in subchondral bone marrow lesions and bone cysts and expansion of subchondral bone in osteoarthritic knees

OBJECTIVESnMeniscal extrusion is often present in knees with OA, and has been associated with cartilage changes. It is unknown whether meniscal extrusion is related to subchondral bone. The aim of the study was to examine the relationship between meniscal extrusion and knee cartilage and subchondral bone, and also changes in these structures over 2 years in a cohort with mild to moderate knee OA.nnnMETHODSnOne hundred and seventeen subjects with knee OA entered the study and underwent MRI on their symptomatic knee at baseline and approximately 2 years later. Meniscal extrusion was assessed at baseline; tibial cartilage volume and plateau bone area, subchondral bone marrow lesions (BMLs) and bone cysts were measured at baseline and follow-up.nnnRESULTSnAt baseline, meniscal extrusion was associated with reduced tibial cartilage volume, increased tibial plateau area, increased prevalence of BMLs and bone cysts in both medial and lateral tibiofemoral compartments (all P < or = 0.001). Baseline medial meniscal extrusion was associated with increased expansion of tibial plateau bone (P = 0.04), increases in BMLs (P = 0.02) and bone cysts (P = 0.003) in the medial tibiofemoral compartment over 2 years.nnnCONCLUSIONSnMeniscal extrusion predicts increases in subchondral bone lesions and tibial plateau bone expansion in patients with knee OA. These data suggest that subchondral bone changes are an early consequence of meniscal extrusion. This may reflect the impaired ability of an extruded meniscus to optimally distribute mechanical loading across the tibial plateau.

Bone marrow lesions predict progression of cartilage defects and loss of cartilage volume in healthy middle-aged adults without knee pain over 2 yrs

OBJECTIVEnIn knee OA, the presence of bone marrow lesions (BMLs) predicts pain and progression of disease. Their occurrence has been described in healthy, pain-free subjects, but whether their presence affects change in cartilage is unknown.nnnMETHODSnTwo hundred and seventy-one healthy community-dwelling adults with no history of knee injury, knee pain or clinical knee OA had an MRI performed on their dominant knee at baseline and 2 yrs later to assess the relationship between the presence of BMLs at baseline and change in tibiofemoral cartilage defects and tibial cartilage volume over 2 yrs.nnnRESULTSnBMLs were present in 37 (14%) subjects. Cartilage defects were more likely to progress rather than remain stable or regress in subjects with BMLs compared with those without BMLs (P = 0.04). The odds of cartilage defects progressing in the tibiofemoral compartment of the knee where BMLs were present compared with where BMLs were absent was 2.6 (95% CI 1.2, 5.3; P = 0.01). Where very large BMLs were present, there was a trend for increased annual tibial cartilage volume loss (46.4 mm(3)/yr; P = 0.07).nnnCONCLUSIONSnThese data suggest that BMLs are associated with change in knee cartilage over 2 yrs in asymptomatic subjects. Increased progression of cartilage defects is seen with increasing size of BMLs. It will be important to determine in future studies whether BMLs directly cause change in cartilage over 2 yrs, or act as a marker of another factor that facilitates these changes.

The relationship between body composition and structural changes at the knee

OBJECTIVEnObesity 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).nnnMETHODSnA total of 153 subjects aged 25-60 years, 81% females, were recruited across a range of BMI (18-55u2009kg/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.nnnRESULTSnThere was an 81 (95% CI: 69, 94) mm3 increase in cartilage volume for every 1u2009kg 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 1u2009kg 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).nnnCONCLUSIONSnIn 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.

Body weight at early and middle adulthood, weight gain and persistent overweight from early adulthood are predictors of the risk of total knee and hip replacement for osteoarthritis

OBJECTIVESnTo examine the relationships between weight at early and middle adulthood and adult weight gain and the risk of total knee and hip replacement for OA.nnnMETHODSnAt baseline interview during 1990-94, 38,149 participants [mean age 54.9 (S.D. 8.6) years] of the Melbourne Collaborative Cohort Study were asked to recall their weight at age 18-21 years and had their middle age height and weight measured. Total knee and hip replacement for OA between 2001 and 2009 was determined by linking the cohort records to the Australian Orthopaedic Association National Joint Replacement Registry.nnnRESULTSnGreater weight and BMI at age 18-21 years and middle age, weight gain and persistent overweight during this time were associated with an increased risk of total knee and hip replacement. Middle age weight [hazard ratio (HR) per 5 kg 1.25 (95% CI 1.23, 1.27) for knee vs 1.11 (1.09, 1.14) for hip] and BMI [HR per 5 kg/m(2) 1.80 (1.72, 1.89) vs 1.29 (1.21, 1.37)] and adult weight gain [HR per 5 kg 1.25 (1.23, 1.28) vs 1.10 (1.07, 1.13)] were more strongly associated with the risk of total knee replacement than total hip replacement (P for heterogeneity of HRs <0.0001).nnnCONCLUSIONnGreater body weight and BMI at early and middle adulthood, weight gain and persistent overweight from early to middle adulthood are risk factors for knee and hip OA. Adult weight gain confers stronger risk on knee OA than hip OA. Weight control from early adulthood and avoiding weight gain are important for the prevention of OA.

Smoking is associated with increased cartilage loss and persistence of bone marrow lesions over 2 years in community-based individuals

OBJECTIVEnTo determine whether smoking is related to change in tibial and patella cartilage, and the development or persistence of bone marrow lesions (BMLs) over 2 years in a cohort of middle-aged adults.nnnMETHODSnTwo hundred and seventy-one adult subjects recruited from the Melbourne Collaborative Cohort Study underwent an MRI of their dominant knee at baseline and approximately 2 years later. Cartilage volume and BMLs were determined for both time points. At baseline, subjects also completed a questionnaire about current and past cigarette smoking.nnnRESULTSnBeing a smoker (former or current) was associated with increased annual loss of medial but not lateral or patella cartilage volume (medial: difference = 13.4 microl, P = 0.03; lateral difference = 4.86 microl, P = 0.45, patella difference = -2.57 microl, P = 0.79). A relationship between increasing pack-years smoked and increased medial cartilage volume loss was also observed (P = 0.04). Amongst people who had a BML at baseline, BMLs present in ever smokers were 11.4 [95% confidence interval (CI) 1.54, 89.9; P = 0.02] times more likely to persist over 2 years than those present in never smokers. In addition, the relationship between smoking and increased medial cartilage loss for subjects with a BML present at baseline was partially mediated by the persistence of the BMLs over 2 years.nnnCONCLUSIONnThis study contributes to the evidence of a detrimental effect of smoking on joint cartilage. Furthermore, it provides a possible mechanism that the association smoking shares with increased cartilage loss may be mediated via smoking impairing the ability for BMLs to resolve.

The association between urban or rural locality and hip fracture in community-based adults: A systematic review

Urban or rural locality has been suggested to influence musculoskeletal health, with lower bone mineral density (BMD) and greater prevalence of fracture identified in urban residents. A computer-aided search of Medline, EMBASE, CINAHL and PsychINFO, January 1966 to November 2007 was conducted to identify studies investigating the relationship between urban or rural locality and the occurrence of hip fracture. The methodological quality of studies was assessed, and a best-evidence synthesis was used to summarise the results. Fourteen cohort studies and one case-control study were identified for inclusion in this review, indicating a lack of literature in the field. Best-evidence analysis identified moderate evidence for residents of rural regions to have lower risk of hip fracture compared to urban residents. Examining principal mechanisms for the observed relationship between urban/rural locality and hip fracture, such as factors at the person or area level, may help to identify modifiable risk factors and inform appropriate prevention strategies.

Association between index-to-ring finger length ratio and risk of severe knee and hip osteoarthritis requiring total joint replacement

OBJECTIVEnThe data are conflicting for the association between the index-to-ring finger length ratio (2D:4D) and the risk of OA. The aim of this cohort study was to examine the relationship between 2D:4D and the risk of severe knee and hip OA requiring total joint replacement.nnnMETHODSnA total of 14 511 participants in the Melbourne Collaborative Cohort Study had 2D:4D assessed from hand photocopies. The incidence of total knee replacement and total hip replacement between 2001 and 2011 was determined by linking the cohort records to the Australian Orthopaedic Association National Joint Replacement Registry.nnnRESULTSnOver an average 10.5 years of follow-up, 580 participants had total knee replacement and 499 had total hip replacement. Greater right 2D:4D [hazard ratio (HR) 0.91 for a s.d. increase in 2D:4D, 95% CI 0.84, 0.99, P = 0.03] and average right and left 2D:4D (HR 0.91 for a s.d. increase in 2D:4D, 95% CI 0.84, 0.99, P = 0.02) were associated with a reduced incidence of total knee replacement. These associations persisted when participants whose fingers had any features that might have affected the validity of 2D:4D measurements were excluded. No significant associations were observed between 2D:4D and the incidence of total hip replacement.nnnCONCLUSIONnA lower 2D:4D is associated with an increased risk of severe knee OA requiring total knee replacement, but not the risk of severe hip OA. The underlying mechanisms for the association warrant further investigation.

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

OBJECTIVEnAlthough 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.nnnMETHODSnA 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.nnnRESULTSnTotal body BMC and BMD was significantly associated with medial cartilage volume in both sexes. However, the associations were stronger in men for BMC (Bu2009=u20090.52; 95% CI 0.21, 0.83; P for differenceu2009=u20090.001) and BMD (Bu2009=u20092242; 95% CI 443, 4041; P for differenceu2009=u20090.05). 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.nnnCONCLUSIONSnIn 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.