Position statement: the epidemiology, pathogenesis and risk factors of osteoarthritis of the knee

Osteoarthritis (OA) represents a large burden on healthcare resources worldwide with continually increasing prevalence. This has led to renewed interest in the causes and pathogenesis of the condition. In recent years, there has been a move away from a simple ‘wear and tear’ model of cartilage to one of a complex inflammatory process involving cellular and extracellular derangements that allow a catabolic state to dominate. Ultimately, OA is now seen as pan-joint disease involving synovium, menisci, ligaments and muscle, in addition to cartilage. There are several classification systems including radiographic, MRI-based, clinical and combined classification systems. As radiographs only detect OA in latter stages, there has been a focus on early diagnosis using MRI and serum biomarkers. New physiological MRI sequences can now measure the proteoglycan content in cartilage and new semiquantitative analyses have been developed to score total knee joint involvement in the disease process. Serum biomarkers can be divided into those that are collagen breakdown products and those that are inflammatory cytokines; these can be used in early detection of OA before radiographic appearances arise. The risk factors for OA include ageing, knee injury, obesity, altered limb alignment, impaired muscle strength, female gender, heavy physical work and genetic susceptibility. Research continues to identify the mechanisms involved that lead to OA development, with possibly unique processes underpinning each risk factor. Our understanding of the pathophysiology of OA will continue to improve in the next few years which should lead to new intervention strategies that target different processes. More informative MRI sequences will continue to be developed and the optimum combination of biomarkers to detect early OA will need to be identified. Genetic studies will continue to identify new susceptibility loci that could be targeted in future therapies. Osteoarthritis (OA) represents a large burden on healthcare resources worldwide with continually increasing prevalence. This has led to renewed interest in the causes and pathogenesis of the condition. In recent years, there has been a move away from a simple ‘wear and tear’ model of cartilage to one of a complex inflammatory process involving cellular and extracellular derangements that allow a catabolic state to dominate. Ultimately, OA is now seen as pan-joint disease involving synovium, menisci, ligaments and muscle, in addition to cartilage. There are several classification systems including radiographic, MRI-based, clinical and combined classification systems. As radiographs only detect OA in latter stages, there has been a focus on early diagnosis using MRI and serum biomarkers. New physiological MRI sequences can now measure the proteoglycan content in cartilage and new semiquantitative analyses have been developed to score total knee joint involvement in the disease process. Serum biomarkers can be divided into those that are collagen breakdown products and those that are inflammatory cytokines; these can be used in early detection of OA before radiographic appearances arise. The risk factors for OA include ageing, knee injury, obesity, altered limb alignment, impaired muscle strength, female gender, heavy physical work and genetic susceptibility. Research continues to identify the mechanisms involved that lead to OA development, with possibly unique processes underpinning each risk factor. Our understanding of the pathophysiology of OA will continue to improve in the next few years which should lead to new intervention strategies that target different processes. More informative MRI sequences will continue to be developed and the optimum combination of biomarkers to detect early OA will need to be identified. Genetic studies will continue to identify new susceptibility loci that could be targeted in future therapies. The Osteoarthritis Research Society International (OARSI) defines osteoarthritis (OA) as ‘a disorder involving movable joints characterized by cell stress and extracellular matrix degradation initiated by micro- and macro-injury that activates maladaptive repair responses including pro-inflammatory pathways of innate immunity’.1OARSI Definition of osteoarthritis.http://oarsi.org/research/standardization-osteoarthritis-definitionsDate: 2015Google Scholar This in turn manifests initially as abnormal joint tissue metabolism, and subsequently by anatomic and physiological derangements. Clinically, this can manifest as cartilage degradation, bone remodelling, osteophyte formation, with patients presenting with joint inflammation, pain and loss of normal joint function (box 1). Box 1Clinical and radiographic diagnostic criteria for osteoarthritis according to the American College of Rheumatology*2Wu CW Morrell MR Heinze E et al.Validation of American College of Rheumatology classification criteria for knee osteoarthritis using arthroscopically defined cartilage damage scores.Semin Arthritis Rheum. 2005; 35: 197-20110.1016/j.semarthrit.2005.06.002Crossref PubMed Scopus (64) Google Scholar1.Knee pain for most days of previous month2.Osteophytes at joint margins on radiographs3.Synovial fluid typical of osteoarthritis (laboratory)4.Age≥40 years5.Crepitus on active joint motion6.Morning stiffness≤30 min duration*Knee osteoarthritis (clinical and radiographic) if 1, 2 or 1, 3, 5, 6 or 1, 4, 5, 6 are present. 1.Knee pain for most days of previous month2.Osteophytes at joint margins on radiographs3.Synovial fluid typical of osteoarthritis (laboratory)4.Age≥40 years5.Crepitus on active joint motion6.Morning stiffness≤30 min duration *Knee osteoarthritis (clinical and radiographic) if 1, 2 or 1, 3, 5, 6 or 1, 4, 5, 6 are present. OA is one of the most common causes of disability in adults. The prevalence increases with age, with a remarkable 13.9% of the population over 25 years old affected, and 33.6% of the population over 65 years old affected.3Lawrence RC Felson DT Helmick CG et al.Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part II.Arthritis Rheum. 2008; 58: 26-3510.1002/art.23176Crossref PubMed Scopus (2860) Google Scholar It has a significant impact on society, compromising quality of life and productivity, and weighs heavily on national healthcare resources.4Le TK Montejano LB Cao Z et al.Health care costs in US patients with and without a diagnosis of osteoarthritis.J Pain Res. 2012; 5: 23-3010.2147/JPR.S27275PubMed Google Scholar 5Bindawas SM Vennu V Auais M Health-related quality of life in older adults with bilateral knee pain and back pain: data from the Osteoarthritis Initiative.Rheumatol Int. 2015; 35: 2095-210110.1007/s00296-015-3309-yCrossref PubMed Google Scholar Costs of OA care have risen over recent decades accounting for up to 1–2.5% of the gross national product for countries such as the USA, Canada, the UK, France and Australia.6March LM Bachmeier CJ Economics of osteoarthritis: a global perspective.Baillieres Clin Rheumatol. 1997; 11: 817-83410.1016/S0950-3579(97)80011-8Abstract Full Text PDF PubMed Scopus (220) Google Scholar The WHO has developed a tool called the disability-adjusted life year to help gauge the burden of musculoskeletal disease on the world's population.7Reginster JY Khaltaev NG Introduction and WHO perspective on the global burden of musculoskeletal conditions.Rheumatology (Oxford). 2002; 41: 1-2Crossref PubMed Google Scholar Figure 1 represents international data collected from the WHO regarding the specific burden of OA worldwide. There is a large and growing burden in developed and developing nations, which will only increase with growing elderly populations.8Brooks PM The burden of musculoskeletal disease—a global perspective.Clin Rheumatol. 2006; 25: 778-78110.1007/s10067-006-0240-3Crossref PubMed Scopus (378) Google Scholar 9Reginster JY The prevalence and burden of arthritis.Rheumatology (Oxford). 2002; 41: 3-610.1093/rheumatology/41.suppl_1.3Crossref PubMed Google Scholar Most of the prevalence statistics originate from Western nations, but the prevalence of symptomatic knee OA in the West appears to be comparable to rural and urban areas within Asia.10Fransen M Bridgett L March L et al.The epidemiology of osteoarthritis in Asia.Int J Rheum Dis. 2011; 14: 113-12110.1111/j.1756-185X.2011.01608.xCrossref PubMed Scopus (188) Google Scholar The Framingham Osteoarthritis Study12Felson DT Naimark A Anderson J et al.The prevalence of knee osteoarthritis in the elderly. The Framingham Osteoarthritis Study.Arthritis Rheum. 1987; 30: 914-91810.1002/art.1780300811Crossref PubMed Google Scholar reported prevalence rates of knee OA in a population in Massachusetts, USA, and a similar population-based study using identical methodology and definitions was performed in the Beijing Osteoarthritis Study.13Zhang Y Xu L Nevitt MC et al.Comparison of the prevalence of knee osteoarthritis between the elderly Chinese population in Beijing and whites in the United States: the Beijing Osteoarthritis Study.Arthritis Rheum. 2001; 44: 2065-207110.1002/1529-0131(200109)44:9<2065::AID-ART356>3.0.CO;2-ZCrossref PubMed Scopus (291) Google Scholar A similar radiographic and symptomatic prevalence of OA was found among Chinese men and their age-matched American counterparts (prevalence ratio 0.9 and 1.02, respectively) but elderly women in Beijing had higher radiographic and symptomatic prevalence rates compared with their age-matched American counterparts (prevalence ratio of 1.45 and 1.43, respectively); possible reasons given were genetic differences and higher physical activity in the Chinese population.13Zhang Y Xu L Nevitt MC et al.Comparison of the prevalence of knee osteoarthritis between the elderly Chinese population in Beijing and whites in the United States: the Beijing Osteoarthritis Study.Arthritis Rheum. 2001; 44: 2065-207110.1002/1529-0131(200109)44:9<2065::AID-ART356>3.0.CO;2-ZCrossref PubMed Scopus (291) Google Scholar Of those with knee OA, lateral compartment OA was much more common in the Chinese population (28.5% in Beijing females vs 11% in Framingham females; 32.3% Chinese males vs 8.8% Framingham males) which has been postulated to arise from more valgus distal femoral alignment.14Felson DT Nevitt MC Zhang Y et al.High prevalence of lateral knee osteoarthritis in Beijing Chinese compared with Framingham Caucasian subjects.Arthritis Rheum. 2002; 46: 1217-122210.1002/art.10293Crossref PubMed Scopus (130) Google Scholar 15Harvey WF Niu J Zhang Y et al.Knee alignment differences between Chinese and Caucasian subjects without osteoarthritis.Ann Rheum Dis. 2008; 67: 1524-152810.1136/ard.2007.074294Crossref PubMed Scopus (26) Google Scholar In sharp contrast, hip OA was 80–90% less prevalent in the Beijing population compared with the Framingham cohort, which may be due to morphological advantages in terms of better hip sphericity and less femora-acetabular impingement.16Dudda M Kim YJ Zhang Y et al.Morphologic differences between the hips of Chinese women and white women: could they account for the ethnic difference in the prevalence of hip osteoarthritis?.Arthritis Rheum. 2011; 63: 2992-299910.1002/art.30472Crossref PubMed Scopus (48) Google Scholar 17Nevitt MC Xu L Zhang Y et al.Very low prevalence of hip osteoarthritis among Chinese elderly in Beijing, China, compared with whites in the United States: the Beijing osteoarthritis study.Arthritis Rheum. 2002; 46: 1773-177910.1002/art.10332Crossref PubMed Scopus (137) Google Scholar Data from the US' National Health and Nutrition Examination Survey (NHANES) as well as a population-based study in Johnston County, North Carolina, showed that knee OA is up to twice as common among African-Americans than Caucasians.18Dillon CF Rasch EK Gu Q et al.Prevalence of knee osteoarthritis in the United States: arthritis data from the Third National Health and Nutrition Examination Survey 1991–94.J Rheumatol. 2006; 33: 2271-2279PubMed Google Scholar 19Jordan JM Helmick CG Renner JB et al.Prevalence of knee symptoms and radiographic and symptomatic knee osteoarthritis in African Americans and Caucasians: the Johnston County Osteoarthritis Project.J Rheumatol. 2007; 34: 172-180PubMed Google Scholar The pattern of OA is also different with African-Americans tending to have more tri-compartmental disease and more severe radiographic changes in the tibiofemoral joint, and lateral joint space narrowing.20Braga L Renner JB Schwartz TA et al.Differences in radiographic features of knee osteoarthritis in African-Americans and Caucasians: the Johnston county osteoarthritis project.Osteoarthritis Cartilage. 2009; 17: 1554-156110.1016/j.joca.2009.07.011Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar Suggested reasons include differences in genetics, obesity, bone mineral density, occupational physical demands, diet and other lifestyle factors.20Braga L Renner JB Schwartz TA et al.Differences in radiographic features of knee osteoarthritis in African-Americans and Caucasians: the Johnston county osteoarthritis project.Osteoarthritis Cartilage. 2009; 17: 1554-156110.1016/j.joca.2009.07.011Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar The prevalence of risk factors for OA also differs between developed and developing nations. In developing nations, for example, obesity is often less prevalent (though now increasing), while higher proportions of the population have occupations requiring heavy physical labour, squatting, kneeling and climbing; the latter may in part explain why knee OA is more common in rural communities of China than in urban ones.10Fransen M Bridgett L March L et al.The epidemiology of osteoarthritis in Asia.Int J Rheum Dis. 2011; 14: 113-12110.1111/j.1756-185X.2011.01608.xCrossref PubMed Scopus (188) Google Scholar Many Asian countries also currently have rapidly ageing populations which will increase the OA burden in the near future.7Reginster JY Khaltaev NG Introduction and WHO perspective on the global burden of musculoskeletal conditions.Rheumatology (Oxford). 2002; 41: 1-2Crossref PubMed Google Scholar OA has historically been seen as an age-related degeneration of articular cartilage, in contrast to the inflammatory destruction of rheumatoid arthritis, and with little regard for other predisposing factors.21Dequeker J Luyten FP The history of osteoarthritis-osteoarthrosis.Ann Rheum Dis. 2008; 67: 5-1010.1136/ard.2007.079764Crossref PubMed Scopus (31) Google Scholar The result being detected at a late stage with reduced joint space on traditional plain radiographs and ultimately joint replacement seen as the only and final solution. There has been a shift from the belief that it is a uniform process mainly affecting articular cartilage to a heterogeneous condition with a plethora of predisposing risk factors working through different pathogenic mechanisms, including inflammation. All tissues within the joint become affected but the loss of articular cartilage and subchondral changes remain the most striking features.22Peterfy CG Guermazi A Zaim S et al.Whole-Organ Magnetic Resonance Imaging Score (WORMS) of the knee in osteoarthritis.Osteoarthritis Cartilage. 2004; 12: 177-19010.1016/j.joca.2003.11.003Abstract Full Text Full Text PDF PubMed Scopus (973) Google Scholar 23Maas O Joseph GB Sommer G et al.Association between cartilage degeneration and subchondral bone remodeling in patients with knee osteoarthritis comparing MRI and (99m)Tc-DPD-SPECT/CT.Osteoarthritis Cartilage. 2015; 23: 1713-172010.1016/j.joca.2015.05.014Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar There is now a focus on early detection with MRI and biochemical markers, thereby allowing earlier, and possibly even preventative, intervention.24Ling SM Patel DD Garnero P et al.Serum protein signatures detect early radiographic osteoarthritis.Osteoarthritis Cartilage. 2009; 17: 43-4810.1016/j.joca.2008.05.004Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar 25Atukorala I Kwoh CK Guermazi A et al.Synovitis in knee osteoarthritis: a precursor of disease?.Ann Rheum Dis. 2016; 75: 390-39510.1136/annrheumdis-2014-205894Crossref PubMed Scopus (132) Google Scholar There has been renewed interest in the biological processes underpinning OA, which alongside better imaging and biochemical analysis has furthered our knowledge greatly. The role of inflammation, synovium, genetics and a variety of biochemical pathways open up the possibilities for more personalised therapy (Table 1, Table 2).Table 1Recent reviewsTitleDateJournalOsteoarthritis year in review 201526Wang Y Teichtahl AJ Cicuttini FM Osteoarthritis year in review 2015: imaging.Osteoarthritis Cartilage. 2016; 24: 49-5710.1016/j.joca.2015.07.027Abstract Full Text Full Text PDF PubMed Google ScholarJanuary 2016Osteoarthritis and CartilageChondropenia: current concept review27Speziali A Delcogliano M Tei M et al.Chondropenia: current concept review.Musculoskelet Surg. 2015; 99: 189-20010.1007/s12306-015-0377-9Crossref PubMed Scopus (15) Google ScholarDecember 2015Musculoskeletal SurgeryCytokines as biochemical markers for knee osteoarthritis28Mabey T Honsawek S Cytokines as biochemical markers for knee osteoarthritis.World J Orthop. 2015; 6: 95-10510.5312/wjo.v6.i1.95Crossref PubMed Scopus (113) Google ScholarJanuary 2015World Journal of OrthopaedicsEarly knee osteoarthritis29Favero M Ramonda R Goldring MB et al.Early knee osteoarthritis.RMD Open. 2015; 1e00006210.1136/rmdopen-2015-000062Crossref PubMed Scopus (65) Google ScholarAugust 2015Rheumatic & Musculoskeletal DiseasesMRI-based semi-quantitative methods for knee osteoarthritis30Jarraya M Hayashi D Roemer FW et al.MR imaging-based semi-quantitative methods for knee osteoarthritis.Magn Reson Med Sci. 2016; 15: 153-16410.2463/mrms.rev.2015-0058Crossref PubMed Scopus (10) Google ScholarDecember 2015Magnetic Resonance in Medical SciencesOsteoarthritis—a case for personalised healthcare31Karsdal MA Christiansen C Ladel C et al.Osteoarthritis—a case for personalized health care?.Osteoarthritis Cartilage. 2014; 22: 7-1610.1016/j.joca.2013.10.018Abstract Full Text Full Text PDF PubMed Scopus (90) Google ScholarJanuary 2014Osteoarthritis and CartilageAdvances and challenges in gene-based approaches for osteoarthritis32Madry H Cucchiarini M Advances and challenges in gene-based approaches for osteoarthritis.J Gene Med. 2013; 15: 343-35510.1002/jgm.2741Crossref PubMed Scopus (38) Google ScholarOctober 2013Journal of Gene MedicineOsteoarthritis: an update with relevance for clinical practice33Bijlsma JW Berenbaum F Lafeber FP Osteoarthritis: an update with relevance for clinical practice.Lancet. 2011; 377: 2115-212610.1016/S0140-6736(11)60243-2Abstract Full Text Full Text PDF PubMed Scopus (1215) Google ScholarJune 2011The Lancet Open table in a new tab Table 2Ten most cited articles on osteoarthritis epidemiology and pathophysiologyTitleDateJournalOsteoarthritis: new insights. Part 1: the disease and its risk factors34Felson DT Lawrence RC Dieppe PA et al.Osteoarthritis: new insights. Part 1: the disease and its risk factors.Ann Intern Med. 2000; 133: 635-646Crossref PubMed Google Scholar2000Annals of Internal MedicineThe American College of Rheumatology criteria for the classification and reporting of osteoarthritis of the hip35Altman R Alarcón G Appelrouth D et al.The American College of Rheumatology criteria for the classification and reporting of osteoarthritis of the hip.Arthritis Rheum. 1991; 34: 505-51410.1002/art.1780340502Crossref PubMed Google Scholar1991Arthritis and RheumatismThe prevalence of knee osteoarthritis in the elderly. The Framingham Osteoarthritis Study12Felson DT Naimark A Anderson J et al.The prevalence of knee osteoarthritis in the elderly. The Framingham Osteoarthritis Study.Arthritis Rheum. 1987; 30: 914-91810.1002/art.1780300811Crossref PubMed Google Scholar1987Arthritis and RheumatismAn update on the epidemiology of knee and hip osteoarthritis with a view to prevention36Felson DT Zhang Y An update on the epidemiology of knee and hip osteoarthritis with a view to prevention.Arthritis Rheum. 1998; 41: 1343-135510.1002/1529-0131(199808)41:8<1343::AID-ART3>3.0.CO;2-9Crossref PubMed Scopus (965) Google Scholar1998Arthritis and RheumatismObesity and knee osteoarthritis: the Framingham Study37Felson DT Anderson JJ Naimark A et al.Obesity and knee osteoarthritis: the Framingham Study.Ann Intern Med. 1988; 109: 18-2410.7326/0003-4819-109-1-18Crossref PubMed Google Scholar1988Annals of Internal MedicineWeight loss reduced the risk for symptomatic knee osteoarthritis in women: the Framingham Study38Felson DT Zhang Y Anthony JM et al.Weight loss reduces the risk for symptomatic knee osteoarthritis in women: the Framingham Study.Ann Intern Med. 1992; 116: 535-53910.7326/0003-4819-116-7-535Crossref PubMed Google Scholar1992Annals of Internal MedicineOsteoarthritis, an inflammatory disease: potential implication for the selection of new therapeutic targets39Pelletier JP Martel-Pelletier J Abramson SB Osteoarthritis, an inflammatory disease: potential implication for the selection of new therapeutic targets.Arthritis Rheum. 2001; 44: 1237-124710.1002/1529-0131(200106)44:6<1237::AID-ART214>3.0.CO;2-FCrossref PubMed Scopus (847) Google Scholar2001Arthritis and RheumatismThe role of cytokines in osteoarthritis pathophysiology40Fernandes JC Martel-Pelletier J Pelletier J-P The role of cytokines in osteoarthritis pathophysiology.Biorheology. 2002; 39: 237-246PubMed Google Scholar2002BiorheologyWhole-organ magnetic resonance imaging score (WORMS) of the knee in osteoarthritis41Peterfy CG Guermazi A Zaim S et al.Whole-organ magnetic resonance imaging score (WORMS) of the knee in osteoarthritis.Osteoarthritis Cartilage. 2004; 12: 177-19010.1016/j.joca.2003.11.003Abstract Full Text Full Text PDF PubMed Scopus (973) Google Scholar2004Osteoarthritis and CartilageArticular cartilage and changes in arthritis. An introduction: cell biology of osteoarthritis42Sandell LJ Aigner T Articular cartilage and changes in arthritis. An introduction: cell biology of osteoarthritis.Arthritis Res. 2001; 3: 107-113Crossref PubMed Scopus (625) Google Scholar2001Arthritis Research Open table in a new tab Plain film radiographs and symptomology have historically been the mainstay of classifying OA. Recently, MRI assessment of the joint has entered clinical practice, while the use of serum and urinary biochemical markers is a rapidly developing research area for early detection. A common factor in radiographic and MRI assessments is the changes that occur in the subchondral bone.43Wluka AE Hanna F Davies-Tuck M et al.Bone marrow lesions predict increase in knee cartilage defects and loss of cartilage volume in middle-aged women without knee pain over 2 years.Ann Rheum Dis. 2009; 68: 850-85510.1136/ard.2008.092221Crossref PubMed Scopus (62) Google Scholar 44Davies-Tuck ML Wluka AE Forbes A et al.Development of bone marrow lesions is associated with adverse effects on knee cartilage while resolution is associated with improvement—a potential target for prevention of knee osteoarthritis: a longitudinal study.Arthritis Res Ther. 2010; 12: R1010.1186/ar2911Crossref PubMed Scopus (0) Google Scholar An emerging concept is that imaging in OA should not only assess cartilage and bone but also the menisci, synovium, fat and muscle, appreciating OA as a ‘whole-organ’ disease (box 2).22Peterfy CG Guermazi A Zaim S et al.Whole-Organ Magnetic Resonance Imaging Score (WORMS) of the knee in osteoarthritis.Osteoarthritis Cartilage. 2004; 12: 177-19010.1016/j.joca.2003.11.003Abstract Full Text Full Text PDF PubMed Scopus (973) Google Scholar Box 2Methods to classify osteoarthritis1. Radiographic Lawrence assessment of Rheum Dis. PubMed Google including of osteoarthritis: 2012; PubMed Scopus Google including knee of and knee CW Morrell MR Heinze E et al.Validation of American College of Rheumatology classification criteria for knee osteoarthritis using arthroscopically defined cartilage damage scores.Semin Arthritis Rheum. 2005; 35: 197-20110.1016/j.semarthrit.2005.06.002Crossref PubMed Scopus (64) Google of symptoms and CW Morrell MR Heinze E et al.Validation of American College of Rheumatology classification criteria for knee osteoarthritis using arthroscopically defined cartilage damage scores.Semin Arthritis Rheum. 2005; 35: 197-20110.1016/j.semarthrit.2005.06.002Crossref PubMed Scopus (64) Google Scholar Radiographic Lawrence assessment of Rheum Dis. PubMed Google Scholar including of osteoarthritis: 2012; PubMed Scopus Google Scholar including knee of and knee CW Morrell MR Heinze E et al.Validation of American College of Rheumatology classification criteria for knee osteoarthritis using arthroscopically defined cartilage damage scores.Semin Arthritis Rheum. 2005; 35: 197-20110.1016/j.semarthrit.2005.06.002Crossref PubMed Scopus (64) Google Scholar of symptoms and CW Morrell MR Heinze E et al.Validation of American College of Rheumatology classification criteria for knee osteoarthritis using arthroscopically defined cartilage damage scores.Semin Arthritis Rheum. 2005; 35: 197-20110.1016/j.semarthrit.2005.06.002Crossref PubMed Scopus (64) Google Scholar strategies for radiographic imaging focus on the changes of joint space subchondral and osteophyte (Table 3, Table imaging classification for osteoarthritis of the the Lawrence assessment of Rheum Dis. PubMed Google of of joint space and possible and possible of joint of joint and and possible of bone joint space severe and of bone Open table in a new tab Table Research Society International (OARSI) for and lateral tibiofemoral joint space of radiographic features in Cartilage. 2007; 15: Full Text Full Text PDF PubMed Google Open table in a new tab plain radiographic imaging classification is the most and has for years, the most of this classification is that it often not detect joint degeneration a more A more of disease is by Advances in MRI have seen better resolution and new sequences developed that improve its to detect bone marrow cartilage and joint fluid changes and osteophyte formation, as well as which often morphological M Ramonda R Goldring MB et al.Early knee osteoarthritis.RMD Open. 2015; 1e00006210.1136/rmdopen-2015-000062Crossref PubMed Scopus (65) Google Scholar of can now be which is the and which MRI sequences that are to detect and measure proteoglycan content within cartilage, the of which is altered early in the disease process sequences currently remain research 2).Table MRI sequences for imaging knee assessment of cartilage collagen semiquantitative on cartilage MRI proteoglycan semiquantitative on cartilage MRI proteoglycan semiquantitative on cartilage MRI proteoglycan content semiquantitative on cartilage MRI of Open table in a new tab MRI of In the most common features that OA are cartilage and subchondral bone SM et model for knee osteoarthritis

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