Kellgren-Lawrence Grading Scale Calculator - Free Score & Interpretation

About the Kellgren-Lawrence Grading Scale

The Kellgren-Lawrence (KL) grading scale is one of the most widely used systems for classifying the radiographic severity of osteoarthritis. Originally developed for knee radiographs, it assigns a single overall grade from 0 (no osteoarthritis) to 4 (severe osteoarthritis) based on the presence and severity of joint space narrowing, osteophytes, subchondral sclerosis, and bone deformity. In clinical research, radiographic osteoarthritis is commonly defined as KL grade 2 or higher. The scale is frequently used to stratify patients in osteoarthritis studies and to define treatment eligibility for interventions such as hyaluronic acid, PRP, and orthobiologics, where mild-to-moderate disease (grades 2-3) is often the target population.

Prevalence:

common

Medical Specialties

Orthopaedics

Rheumatology

Radiology

Anatomic Areas

Knee

Hip

Clinical Indications

Knee Osteoarthritis

Hip Osteoarthritis

Radiographic Oa Severity

Cohort Stratification

Treatment Eligibility

Research Studies

Developer Information

Developed by John H. Kellgren and James S. Lawrence at the University of Manchester. First published in 1957 in the Annals of the Rheumatic Diseases based on a population study of knee and hand osteoarthritis using standardised anteroposterior radiographs.

Copyright & Licensing

The Kellgren-Lawrence classification is in the public domain. The original 1957 publication is widely cited and freely referenced in clinical and research settings. No licensing restrictions apply.

Administration Instructions

Review the weight-bearing radiograph and select the Kellgren-Lawrence grade that best describes the overall osteoarthritis severity for this joint. Radiographic osteoarthritis is typically defined as minimal grade or higher.

Scoring Methodology

The Kellgren-Lawrence scale assigns a single ordinal grade from 0 to 4 based on overall radiographic assessment of the joint. Grade 0 indicates definite absence of osteoarthritis changes. Grade 1 indicates doubtful joint space narrowing with possible osteophytic lipping. Grade 2 indicates definite osteophytes with possible joint space narrowing and represents the threshold for minimal radiographic osteoarthritis. Grade 3 indicates moderate multiple osteophytes, definite joint space narrowing, some sclerosis, and possible bone end deformity. Grade 4 indicates large osteophytes, marked joint space narrowing, severe sclerosis, and definite bone end deformity. The score equals the assigned grade (0-4). Lower scores indicate less severe radiographic disease. In most epidemiological and clinical studies, established radiographic osteoarthritis is defined as KL grade >= 2.

Scoring:

Lower is better

Meaningful Change Threshold

Progression of Kellgren-Lawrence grade by one or more levels over time is considered radiographic progression of osteoarthritis. Short-term changes in KL grade are uncommon; meaningful progression is typically assessed over intervals of 1-2 years or longer in longitudinal studies.

Score Interpretation

Understanding what your score means

grade 0

None - Physiological joint with healthy cartilage. Well-preserved space, no bone spurs, and no sclerosis.

grade 1

Doubtful - Doubtful joint space narrowing with possible small, early osteophytes. Often not classified as established radiographic osteoarthritis.

grade 2

Minimal - Definite osteophytes and possible early joint space narrowing. Threshold for established radiographic osteoarthritis. Common eligibility range for injectable treatments.

grade 3

Moderate - Multiple moderate osteophytes, definite joint space narrowing, early bone sclerosis, and possible bone deformity.

grade 4

Severe - Large osteophytes, marked or complete joint space collapse, severe bone sclerosis, and definite bone end deformity (bone-on-bone).

Subscales

This questionnaire measures multiple dimensions

Clinical Limitations & Considerations

The Kellgren-Lawrence system combines multiple radiographic features into a single ordinal grade, which limits granular assessment of individual features such as joint space width or osteophyte size. Inter-observer and intra-observer reliability is moderate, and numerous methodological variations exist across studies. The scale was originally developed for knee radiographs but is also applied to hip and other joints without universal validation. Radiographic severity correlates imperfectly with clinical symptoms. Grade 1 is often excluded from definitions of established osteoarthritis. Weight-bearing radiographs are recommended for knee assessment but are not always used consistently.

Supporting Literature

Key validation and development studies for the Kellgren-Lawrence Grading Scale

1

Classifications in Brief: Kellgren-Lawrence Classification of Osteoarthritis

Schiphof D, van Middelkoop M, Bierma-Zeinstra SM, Koes BW, Bindels PJ, Kuijpers T

Clinical Orthopaedics and Related Research, 2016

DOI: 10.1007/s11999-016-4732-4

Used in Literature

Studies and publications that have used the Kellgren-Lawrence Grading Scale

1

Classifications in Brief: Kellgren-Lawrence Classification of Osteoarthritis

Schiphof D, van Middelkoop M, Bierma-Zeinstra SM, Koes BW, Bindels PJ, Kuijpers T

Clinical Orthopaedics and Related Research, 2016

DOI: 10.1007/s11999-016-4732-4
2

Kellgren/Lawrence Grading in Cohort Studies: Methodological Update and Implications Illustrated Using Data From a Dutch Hip and Knee Cohort

van der Esch M, Klapwijk LB, Kroon HM, et al.

Arthritis Care & Research, 2022

DOI: 10.1002/acr.24563

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