Einstein International Journal Organization(EIJO)

Abstract

Background: Knee osteoarthritis (OA) is conventionally staged using the Kellgren–Lawrence (KL) radiographic grading system, but plain radiographs assess only bony changes and may underestimate soft-tissue pathology detectable on magnetic resonance imaging (MRI).

Objective: To correlate KL radiographic grade with MRI-detected structural changes (cartilage loss, osteophytes, bone marrow lesions, meniscal and other soft-tissue abnormalities) in patients with knee OA.

Methods: This retrospective comparative study analysed 35 knees with paired weight-bearing radiographs and MRI. KL grade was extracted from radiology records, and a composite MRI structural severity grade (0–4) was assigned based on cartilage, osteophyte and bone marrow findings. Agreement was assessed using Spearman's rank correlation and quadratic-weighted kappa; diagnostic performance of KL grade ≥2 for detecting moderate-or-worse MRI change was also calculated.

Results: Mean age was 48.4 ± 9.0 years (range 34–71); 24 (68.6%) were female. KL grade distribution was 0 in 6 (17.1%), 1 in 11 (31.4%) and 2 in 18 (51.4%) knees. MRI showed cartilage abnormality in 34/35 (97.1%) knees, including all six KL-0 knees. Correlation between KL and MRI grade was weak and non-significant (Spearman's ρ = 0.05, p = 0.78; weighted κ = 0.06). Exact agreement occurred in 28.6% of knees and agreement within one grade in 74.3%; MRI grade exceeded KL grade in 57.1%. Sensitivity of KL ≥2 for MRI-moderate-or-worse change was 50.0% and specificity 44.4%.

Conclusion: KL radiographic grading correlated poorly with MRI-detected structural severity in this cohort, and MRI identified cartilage and soft-tissue pathology even in radiographically normal knees, supporting MRI's superior sensitivity for early structural OA change.

Keywords: Osteoarthritis, Knee, Magnetic Resonance Imaging, Radiography; Severity of Illness Index, Cartilage, Articular

1. Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis. 1957;16(4):494-502.
2. Kohn MD, Sassoon AA, Fernando ND. Classifications in brief: Kellgren-Lawrence classification of osteoarthritis. Clin Orthop Relat Res. 2016;474(8):1886-93.
3. Schiphof D, Boers M, Bierma-Zeinstra SM. Differences in descriptions of Kellgren and Lawrence grades of knee osteoarthritis. Ann Rheum Dis. 2008;67(7):1034-6.
4. Culvenor AG, Engen CN, Øiestad BE, Engebretsen L, Risberg MA. Defining the presence of radiographic knee osteoarthritis: a comparison between the Kellgren and Lawrence system and OARSI atlas criteria. Knee Surg Sports Traumatol Arthrosc. 2015;23(12):3532-9.
5. Peterfy CG, Guermazi A, Zaim S, Tirman PFJ, Miaux Y, White D, et al. Whole-organ magnetic resonance imaging score (WORMS) of the knee in osteoarthritis. Osteoarthritis Cartilage. 2004;12(3):177-90.
6. Hunter DJ, Guermazi A, Lo GH, Grainger AJ, Conaghan PG, Boudreau RM, et al. Evolution of semi-quantitative whole joint assessment of knee OA: MOAKS (MRI Osteoarthritis Knee Score). Osteoarthritis Cartilage. 2011;19(8):990-1002.
7. Park HJ, Kim SS, Lee SY, et al. A practical MRI grading system for osteoarthritis of the knee: association with Kellgren-Lawrence radiographic scores. Eur J Radiol. 2013;82(1):112-7.
8. Hayes CW, Jamadar DA, Welch GW, Jannausch ML, Lachance LL, Capul DC, et al. Osteoarthritis of the knee: comparison of MR imaging findings with radiographic severity measurements and pain in middle-aged women. Radiology. 2005;237(3):998-1007.
9. Cicuttini FM, Wluka AE, Forbes A, Wolfe R. Comparison of tibial cartilage volume and radiologic grade of the tibiofemoral joint. Arthritis Rheum. 2003;48(3):682-8.
10. Harada Y, Tokuda O, Fukuda K, et al. Relationship between cartilage volume using MRI and Kellgren-Lawrence radiographic score in knee osteoarthritis with and without meniscal tears. AJR Am J Roentgenol. 2011;196(3):298-304.
11. Lee DW, Kim JS, Han HS, Ro DH. Longitudinal correlation between X-ray and MRI findings in medial compartment knee osteoarthritis: insights into early cartilage loss and structural changes. Knee Surg Sports Traumatol Arthrosc. 2026;34(6):2047-56.
12. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics. 1977;33(1):159-74.
13. Guermazi A, Hunter DJ, Roemer FW. Plain radiography and magnetic resonance imaging diagnostics in osteoarthritis: validated staging and scoring. J Bone Joint Surg Am. 2009;91 Suppl 1:54-62.
14. Altman RD, Gold GE. Atlas of individual radiographic features in osteoarthritis, revised. Osteoarthritis Cartilage. 2007;15 Suppl A: A1-56.
15. Favero M, Ramonda R, Goldring MB, Goldring SR, Punzi L. Early knee osteoarthritis. RMD Open. 2015;1(1):e000062.