Tibial subchondral bone size and knee cartilage defects: relevance to knee osteoarthritis

Magnitude and regional distribution of cartilage loss associated with grades of joint space narrowing in radiographic osteoarthritis--data from the Osteoarthritis Initiative (OAI)

OBJECTIVE

Clinically, radiographic joint space narrowing (JSN) is regarded a surrogate of cartilage loss in osteoarthritis (OA). Using magnetic resonance imaging (MRI), we explored the magnitude and regional distribution of differences in cartilage thickness and subchondral bone area associated with specific Osteoarthritis Research Society International (OARSI) JSN grades.

METHOD

Seventy-three participants with unilateral medial JSN were selected from the first half (2678 cases) of the OA Initiative cohort (45, 21, and 7 with OARSI JSN grades 1, 2, and 3, respectively, no medial JSN in the contra-lateral knee). Bilateral sagittal baseline DESSwe MRIs were segmented by experienced operators. Intra-person between-knee differences in cartilage thickness and subchondral bone areas were determined in medial femorotibial subregions.

RESULTS

Knees with medial OARSI JSN grades 1, 2, and 3 displayed a 190 microm (5.2%), 630 microm (18%), and 1560 microm (44%) smaller cartilage thickness in weight-bearing medial femorotibial compartments compared to knees without JSN, respectively. The weight-bearing femoral condyle displayed relatively greater differences than the posterior femoral condyle or the medial tibia (MT). The central subregion within the weight-bearing medial femur (cMF) of the femoral condyle (30-75 degrees ), and the external and central subregions within the tibia displayed relatively greater JSN-associated differences compared to other medial femorotibial subregions. Knees with higher JSN grades also displayed larger than contra-lateral femorotibial subchondral bone areas.

CONCLUSIONS

This study provides quantitative estimates of JSN-related cartilage loss, with the central part of the weight-bearing femoral condyle being most strongly affected. Knees with higher JSN grades displayed larger subchondral bone areas, suggesting that an increase in subchondral bone area occurs in advanced OA.

Femorotibial subchondral bone area and regional cartilage thickness: a cross-sectional description in healthy reference cases and various radiographic stages of osteoarthritis in 1,003 knees from the Osteoarthritis Initiative

OBJECTIVE

To identify structural differences in total subchondral bone area (tAB) and cartilage thickness between healthy reference knees and knees with radiographic osteoarthritis (OA).

METHODS

Baseline magnetic resonance images from 1 knee of 1,003 Osteoarthritis Initiative participants were studied: 112 healthy reference knees without radiographic OA, symptoms, or risk factors; 70 preradiographic OA knees (calculated Kellgren/Lawrence [K/L] grade 0/1); and 821 radiographic OA knees (calculated K/L grade ≥2). Means and standard (Z) scores (SD unit differences compared with normal subjects) of the tAB and regional cartilage thickness were assessed in the weight-bearing femorotibial joint and compared between groups.

RESULTS

In men, tAB was 8.2% larger in preradiographic OA knees and 6.6%, 8.1%, and 8.5% larger in calculated K/L grade 2, 3, and 4 radiographic OA knees, respectively, than in reference knees. In women, the differences were +6.8%, +7.3%, +9.9%, and +8.1%, respectively. The external medial tibia showed the greatest reduction in cartilage thickness (Z scores -5.1/-5.6 in men/women) with Osteoarthritis Research Society International medial joint space narrowing (JSN) grade 3, and the external lateral tibia (Z scores -6.0 for both sexes) showed the greatest reduction with lateral JSN grade 3. In all subregions of end-stage radiographic OA knees, ≥25% of the average normal cartilage thickness was maintained. An overall trend toward thicker cartilage was found in preradiographic OA and calculated K/L grade 2 knees, especially in the external central medial femur.

CONCLUSION

tABs were larger in preradiographic OA and radiographic OA knees than in healthy reference knees, and the difference did not become larger with higher calculated K/L grades. Specific subregions with substantial cartilage thickening or thinning were identified in pre-, early, and late radiographic OA.

Region of interest analysis: by selecting regions with denuded areas can we detect greater amounts of change?

INTRODUCTION

Based on recent analyses, the measures of short-term responsiveness of magnetic resonance imaging (MRI) derived cartilage morphometry may not be as large as earlier studies had suggested. We examined if by selecting regions of interest with denuded cartilage, the remaining cartilage within this region of interest was susceptible to greater rates of cartilage loss.

METHODS

Subjects included for this analysis are a subset of the approximately 4700 participants in the Osteoarthritis Initiative (OAI) Study. Bilateral radiographs and 3T MRI (Siemens Trio) of the knees and clinical data are obtained at baseline and annually in all participants. Hundred and fifty subjects from the OAI progression subcohort all of whom had both frequent symptoms and, in the same knee, radiographic osteoarthritis (ROA defined as definite tibio-femoral osteophytes on X-ray) based on a screening reading done at the OAI clinics. One knee from each subject was selected for analysis. Using sagittal 3D DESSwe MR images from the baseline and 12-month follow-up visit, a segmentation algorithm was applied to the cartilage plates of the index knee to compute the cartilage volume, normalized cartilage volume (volume normalized to bone surface interface area), and percent denuded area (Total Cartilage Bone Interface area denuded of cartilage). Summary statistics of the changes (absolute and percentage) from baseline at 1 year and the standardized response mean (SRM), i.e., mean change divided by the standard deviation (SD) of that change were calculated. Analyses are stratified into three groups according to baseline assessment of denuded area: those with no denuded area in the region of interest at baseline, and then two groups (intermediate denuded area (<or=median) and severe (>or=median) denuded area) of equal sample size.

RESULTS

On average the subjects were 60.9 years of age and obese with a mean body mass index (BMI) of 30.3 kg/m(2). For the combined central medial femur and tibia the mean volume change for the whole sample was -48.2 (SD 159.8) mm(3), which gives an SRM of -0.30. In the subsample of knees with no denuded area the SRM was -0.25, in the knees with intermediate denuded area the SRM was -0.30, and in knees with severe denuded area the SRM was -1.00. For normalized volume of the central medial femur in the subsample of knees with no denuded area the SRM was -0.22, in the knees with intermediate denuded area the SRM was -0.26, and in knees with severe denuded area (n=23) the SRM was -0.71. The magnitude of the SRMs was generally smaller in participants with no denuded area. In contrast, the SRMs in participants with denuded area were larger.

CONCLUSION

By selecting participants with the presence of cartilage regions with denuded area the ability to demonstrate change in cartilage loss in that specific location is markedly improved compared to persons without a full thickness lesion in that cartilage plate. This option for screening during recruitment in clinical trials could facilitate the detection of participants at greater risk of subsequent cartilage loss.

Do NSAIDs affect longitudinal changes in knee cartilage volume and knee cartilage defects in older adults?

BACKGROUND

The effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on knee osteoarthritis progression are unclear. The aim of this longitudinal study was to determine the associations between use of NSAIDs and changes in knee cartilage volume and knee cartilage defects over 2.9 years in older adults.

METHODS

T(1)-weighted fat-suppressed magnetic resonance imaging on the right knee was performed in a total of 395 randomly selected subjects (mean age 62 years, range 51-80 years, and 50% female) to assess knee cartilage volume at tibial sites and knee cartilage defects (0-4 scale) at baseline and 2.9 years later. Medication use in the last month was recorded by questionnaire.

RESULTS

Compared with nonusers of NSAIDs (n = 334), users of cyclooxygenase (COX)-2 inhibitors (n = 40) had decreased knee cartilage defect development in the medial tibiofemoral compartment (odds ratio [OR] 0.4, 95% confidence interval [CI], 0.2-0.99), whereas users of conventional NSAIDs (n = 21) had increased knee cartilage defect development in both medial (OR 3.1, 95% CI, 1.0-9.1) and lateral (OR 2.6, 95% CI, 1.0-6.7) tibiofemoral compartments. Comparing users of COX-2 inhibitors with users of conventional NSAIDs, the latter had higher knee cartilage volume loss (-5.3% vs -3.1% at medial tibia and -3.6% vs -1.1% at lateral tibia; all P <.05). All associations were adjusted for potential confounders including knee pain and radiographic osteoarthritis.

CONCLUSIONS

This study suggests that nonselective NSAIDs may have deleterious effects, while selective COX-2 inhibitors might have beneficial effects on knee cartilage. Randomized controlled trials examining knee structure to confirm this finding are warranted.

Cartilage defects are associated with physical disability in obese adults

OBJECTIVE

To describe the associations between physical disability measures and knee cartilage defects in obese adults.

METHODS

One hundred and eleven obese subjects were recruited from laparoscopic adjustable gastric banding or exercise/diet weight loss programmes. All subjects completed disease-specific (WOMAC) and general health status (SF-36) questionnaires, and were assessed for range of knee motion, tibiofemoral alignment and quadriceps strength. Knee cartilage defects were graded on MRI according to established protocol. Regression analysis was adjusted for age, gender, BMI and presence of clinical knee OA.

RESULTS

The association between higher whole compartment cartilage defect scores and increasing BMI, age and clinical knee OA was confirmed in this obese cohort (r = 0.27, P = 0.01; r = 0.26, P = 0.007; P < 0.0001, respectively), whereas new associations were found with reduced knee range of motion (r = 0.5, P < 0.0001). No associations were found between defect scores and quadriceps strength. Varus malalignment was associated with higher medial cartilage defect scores (r = 0.33, P = 0.013). Higher levels of pain, stiffness and physical disability (WOMAC, SF-36) were associated with higher medial compartment and patella cartilage defect scores.

CONCLUSIONS

Knee cartilage defects increase with increasing obesity and are associated with both objective and self-reported measures of physical disability. Longitudinal studies are required to assess the potential for change or improvement in cartilage defects with weight loss.

A novel in vivo murine model of cartilage regeneration. Age and strain-dependent outcome after joint surface injury

OBJECTIVES

To generate and validate a murine model of joint surface repair following acute mechanical injury.

METHODS

Full thickness defects were generated in the patellar groove of C57BL/6 and DBA/1 mice by microsurgery. Control knees were either sham-operated or non-operated. Outcome was evaluated by histological scoring systems. Apoptosis and proliferation were studied using TUNEL and Phospho-Histone H3 staining, respectively. Type II collagen neo-deposition and degradation were evaluated by immunostaining using antibodies to the CPII telopeptide and C1,2C (Col2-3/4Cshort), respectively. Aggrecanases and matrix metalloproteinases (MMPs) activity were assessed by immunostaining for TEGE(373) and VDIPEN neo-epitopes.

RESULTS

Young 8-week-old DBA/1 mice displayed consistent and superior healing of the articular cartilage defect. Age-matched C57BL/6 mice repaired poorly and developed features of osteoarthritis (OA). Compared to C57BL/6, DBA/1 mice displayed a progressive decline of chondrocyte apoptosis, cell proliferation within the repair tissue, persistent type II collagen neo-deposition, less type II collagen degradation, less aggrecanases and more MMP-induced aggrecan degradation. Eight-month-old DBA/1 mice failed to repair, but, in contrast to age-matched C57BL/6 mice, developed no signs of OA.

CONCLUSION

We have generated and validated a murine model of cartilage regeneration in which the outcome of joint surface injury is strain and age dependent. This model will allow, for the first time, the dissection of different pathways involved in joint surface regeneration in adult mammals using the powerful technology of mouse genetics.

Serum levels of vitamin D, sunlight exposure, and knee cartilage loss in older adults: the Tasmanian older adult cohort study

OBJECTIVE

To determine the associations between serum levels of vitamin D, sunlight exposure, and knee cartilage loss cross-sectionally and longitudinally in older adults.

METHODS

A total of 880 randomly selected subjects (mean age 61 years [range 51-79 years], 50% women) were studied at baseline, and 353 of these subjects were studied 2.9 years later. Serum levels of 25-hydroxyvitamin D (25[OH]D) were assessed by radioimmunoassay, and sunlight exposure was assessed by questionnaire. T1-weighted fat-suppressed magnetic resonance imaging (MRI) of the right knee was performed to determine knee cartilage volume and defects. Knee radiographic osteoarthritis (OA) and knee pain were also assessed.

RESULTS

The mean 25(OH)D serum level was 52.8 nmoles/liter at baseline (range 13-119 nmoles/liter). Winter sunlight exposure and serum 25(OH)D level were both positively associated with medial and lateral tibial cartilage volume, and a serum 25(OH)D level<50 nmoles/liter was associated with increased medial tibiofemoral joint space narrowing (all P<0.05). Longitudinally, baseline serum 25(OH)D level predicted change in both medial and lateral tibial cartilage volume (beta=+0.04% per annum per nmole/liter for both; P<0.05), and change in serum 25(OH)D level was positively associated with change in medial tibial cartilage volume. These associations were consistent in subjects with radiographic OA and knee pain and/or in women, but not in men or in subjects without radiographic OA or knee pain.

CONCLUSION

Sunlight exposure and serum 25(OH)D levels are both associated with decreased knee cartilage loss (assessed by radiograph or MRI). This is best observed using the whole range of 25(OH)D levels rather than predefined cut points and implies that achieving vitamin D sufficiency may prevent and/or retard cartilage loss in knee OA.

Imaging of knee osteoarthritis

New imaging modalities are broadening the possibilities in osteoarthritis (OA) research, and are offering new insights to help better understand the pathogenesis of this disease. Although knee radiographs are widely employed in epidemiological and clinical studies to assess structural pathology, joint radiographs provide limited outcome measures in knee OA, and other more valid, reliable and sensitive imaging modalities are now available. In particular, magnetic resonance imaging can directly visualize articular cartilage and other joint structures, such as bone and soft tissue, that are now recognized as part of the disease process. This chapter will examine imaging modalities in the assessment of knee OA, and the impact of these on our understanding of the pathogenesis of this disease.

A pilot study of the reproducibility and validity of measuring knee subchondral bone density in the tibia

OBJECTIVE

To describe the reproducibility and validity of six different measurement techniques for knee subchondral bone mineral density (sBMD).

METHODS

A consecutive sample of 50 male and female participants from a population-based longitudinal study had sBMD assessed using dual energy X-ray absorptiometry scans. Anthropometric, knee pain, cartilage and bone measures by magnetic resonance imaging and radiographic osteoarthritis (OA) were assessed. The six methods were defined as: (1) the midpoint of one intercondylar spine, across the tibial surface and descending 10mm; from the midpoint of the two intercondylar spines (2) the top of the spine descending 20mm, (3) 10-20mm beneath the top of the spine; from the tibial surface descending, (4) 10mm, (5) 15 mm, and (6) 20mm.

RESULTS

All six methods had excellent reproducibility (intra-class correlation coefficient 0.98-1.00). sBMD was higher in males (methods 2-4) and higher in those with medial tibial osteophytes (methods 1, 3 and 4). Medial tibial cartilage defects and overall cartilage defects correlated with sBMD (methods 3 and 4). Method 2, which includes the intercondylar spine, correlated with medial tibial bone size. Measuring sBMD using methods 3 and 4 produced the greatest number of associations with joint features of OA.

CONCLUSIONS

These preliminary results need confirmation in larger longitudinal samples but suggest that sBMD can be accurately measured and plays a role in knee OA. Methods 3 and 4 had the best concurrent validity; however, method 2 adds additional information on tibial bone size, suggesting that two measures are necessary in clinical studies.

Angiogenesis in osteoarthritis

PURPOSE OF REVIEW

Much has been documented in recent years on the possible involvement of angiogenesis in osteoarthritis. An understanding of the various regulatory mechanisms controlling blood vessel growth in the joint should lead to novel therapeutics, which selectively inhibit undesirable angiogenesis. Here, we summarize recent findings on the roles of angiogenesis in osteoarthritis and place this evidence in the context of previous literature in order to help explain pain and disease progression.

RECENT FINDINGS

Inflammation and angiogenesis are closely associated in osteoarthritis, modulating functions of chondrocytes, contributing towards abnormal tissue growth and perfusion, ossification and endochondral bone development, leading to radiographic changes observed in the joint. Innervation accompanies vascularization and inflammation, hypoxia and mechanical overload are all thought to contribute in sensitizing these new nerves leading to increased pain. Articular cartilage provides a unique environment in which blood vessel growth is regulated by endogenous angiogenesis inhibitors and matrix constituents, as well as by growth factors produced by chondrocytes, subchondral bone and synovium. MRI and ultrasound enable the in-vivo visualization of abnormal vascularity in synovium and subchondral bone that have not been apparent with conventional radiography. As a result of these new findings, the widely accepted notion that osteoarthritis is primarily a disease of the cartilage is being challenged.

SUMMARY

Molecular mechanisms and consequences of angiogenesis in osteoarthritis are slowly being elucidated. Studies, both in humans and animal models, support the notion that inhibiting angiogenesis will provide effective therapeutic strategies for treating osteoarthritis. Better techniques that can more precisely visualize the vascular changes of the whole joint can further enhance our understanding of osteoarthritis, and can provide proof of concept and early evidence of efficacy in trials of novel therapeutic interventions.

Anterior cruciate ligament failure and cartilage damage during knee joint compression: a preliminary study based on the porcine model

BACKGROUND

Anterior cruciate ligament (ACL) injury incurred from high-impact activities leads to an increased risk of osteoarthritis.

HYPOTHESIS

Impact forces that cause ACL failure can also inflict cartilage damage, whereby its extent and distribution may be influenced by the ligament failure mechanism.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Six porcine knee specimens were mounted to a material testing system at 70 degrees of flexion. During compression, rotational and translational data of the specimens were recorded with a motion-capture system. Compression was successively repeated with increasing actuator displacement until a significant drop in compressive force response was observed; ligament failure was assessed by dissection. Osteocartilage explants were extracted from the meniscus-covered sites (anterior, exterior, and posterior) and exposed (interior) sites on both tibial compartments. The explants were sectioned, stained, and histologically scored using the modified Mankin grading system.

RESULTS

Five of the 6 specimens incurred ACL failure. On failure, a significant compressive force drop (1812.5-2659.3 N) was observed together with considerable posterior femoral translation; 2 specimens underwent external rotation, while 2 had internal rotation and 1 had no substantial rotation. Generally, the meniscus-covered sites displayed significant surface fraying and occasional deep clefts; the exposed site did not present substantial surface irregularities but indicated more tidemark disruption. Higher Mankin scores observed at certain sites illustrated a localized presence of contact and shear forces, which may be caused by pivoting and sliding of the femoral condyles during rotation.

CONCLUSION

The porcine model can be a tenable preliminary option for assessing the role of the human ACL during joint compression. Impact loads that result in ligament failure can potentially inflict considerable cartilage damage; the damage profile may be affected by the type of failure mechanism.

CLINICAL RELEVANCE

Cartilage injury arising at the time of ACL injury may lead to an accelerated risk of joint degeneration.

Epiphyseal expansion in hand bones: association with age, sex, and hand osteoarthritis

OBJECTIVES

Previous studies showed increased femoral, neck, and tibial plateau with age in individuals with and without osteoarthritis (OA) at adjacent joints. However, the question whether epiphyseal bone enlargement is a natural phenomenon of aging or associated with OA remains open. The aim of the present study was to evaluate age- and sex-related changes in the relative size of epiphyses of long hand bones and their association with radiographic OA.

DESIGN

The data were collected from a population-based European sample in 1994 (557 individuals) and in 2002 (513 individuals). The latter sample included 253 individuals who were previously investigated in 1994. The epiphyseal index (EI), reflecting the relative size of bone epiphyses and hand OA, was evaluated from hand radiographs. Statistical analyses included multiple regression analyses and a maximum likelihood-based model-fitting technique.

RESULTS

Hand bone epiphyses increased with age and with OA. In males, the EI gradually increased during their entire life span. In females, the EI remained almost unchanged up to the age of 40, after which, it increased more rapidly than in males. Individuals with OA had higher values of EI at any age. In both sexes, epiphyseal enlargement is a predisposing factor for hand OA progression in adjacent joints. This was clearly seen in males, where old individuals with high EI values had much higher OA scores in comparison with age-matched individuals.

CONCLUSIONS

Enlargement of long bone epiphyses with age appears to be a general tendency in the human skeleton. Our study shows that the enlargement of epiphyses may also be related to OA.

Osteoarthritis

Osteoarthritis (OA) is characterized by degeneration of articular cartilage, limited intraarticular inflammation with synovitis, and changes in peri-articular and subchondral bone. Multiple factors are involved in the pathogenesis of OA, including mechanical influences, the effects of aging on cartilage matrix composition and structure, and genetic factors. Since the initial stages of OA involve increased cell proliferation and synthesis of matrix proteins, proteinases, growth factors, cytokines, and other inflammatory mediators by chondrocytes, research has focused on the chondrocyte as the cellular mediator of OA pathogenesis. The other cells and tissues of the joint, including the synovium and subchondral bone, also contribute to pathogenesis. The adult articular chondrocyte, which normally maintains the cartilage with a low turnover of matrix constituents, has limited capacity to regenerate the original cartilage matrix architecture. It may attempt to recapitulate phenotypes of early stages of cartilage development, but the precise zonal variations of the original cartilage cannot be replicated. Current pharmacological interventions that address chronic pain are insufficient, and no proven structure-modifying therapy is available. Cartilage tissue engineering with or without gene therapy is the subject of intense investigation. There are multiple animal models of OA, but there is no single model that faithfully replicates the human disease. This review will focus on questions currently under study that may lead to better understanding of mechanisms of OA pathogenesis and elucidation of effective strategies for therapy, with emphasis on mechanisms that affect the function of chondrocytes and interactions with surrounding tissues.

Effects of laterally wedged insoles on symptoms and disease progression in medial knee osteoarthritis: a protocol for a randomised, double-blind, placebo controlled trial

BACKGROUND

Whilst laterally wedged insoles, worn inside the shoes, are advocated as a simple, inexpensive, non-toxic self-administered intervention for knee osteoarthritis (OA), there is currently limited evidence to support their use. The aim of this randomised, double-blind controlled trial is to determine whether laterally wedges insoles lead to greater improvements in knee pain, physical function and health-related quality of life, and slower structural disease progression as well as being more cost-effective, than control flat insoles in people with medial knee OA.

METHODS/DESIGN

Two hundred participants with painful radiographic medial knee OA and varus malalignment will be recruited from the community and randomly allocated to lateral wedge or control insole groups using concealed allocation. Participants will be blinded as to which insole is considered therapeutic. Blinded follow up assessment will be conducted at 12 months after randomisation. The outcome measures are valid and reliable measures recommended for OA clinical trials. Questionnaires will assess changes in pain, physical function and health-related quality-of-life. Magnetic resonance imaging will measure changes in tibial cartilage volume. To evaluate cost-effectiveness, participants will record the use of all health-related treatments in a log-book returned to the assessor on a monthly basis. To test the effect of the intervention using an intention-to-treat analysis, linear regression modelling will be applied adjusting for baseline outcome values and other demographic characteristics.

DISCUSSION

Results from this trial will contribute to the evidence regarding the effectiveness of laterally wedged insoles for the management of medial knee OA.

TRIAL REGISTRATION

ACTR12605000503628; NCT00415259.