Classification system
Kellgren-Lawrence Classification
Kellgren-Lawrence Classification of Osteoarthritis
The Kellgren-Lawrence classification grades radiographic osteoarthritis from 0 to 4 based on osteophyte formation, joint space narrowing, subchondral sclerosis and bone contour deformity, with grade 2 conventionally taken as the threshold for definite radiographic osteoarthritis.
What the Kellgren-Lawrence category means
Kellgren-Lawrence scores run from 0 to 4, where a lower score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.
- None0–0
- Doubtful1–1
- Minimal2–2
- Moderate3–3
- Severe4–4
Published criteria and reliability
The published cut-offs that define this instrument, and the measured agreement between observers using it. Each is reported with the population it was derived in.
| Type | Value | Subscale | Population | Follow-up | Source |
|---|---|---|---|---|---|
| Criterion | Grade ≥ 2 defines radiographic osteoarthritis | — | Epidemiological studies and trial entry criteria | — | Kellgren JH 1957 |
| Criterion | Interobserver agreement is moderate overall and poorest at grades 1 and 2 | — | Radiologists and orthopaedic surgeons | — | Schiphof D 2008 |
| Criterion | Published definitions of the grades differ between sources, which is itself a source of disagreement | — | Systematic review of KL definitions in the literature | — | Schiphof D 2008 |
Criterion is a published cut-off, definition or performance figure belonging to a classification or decision rule — it is not a change score and should not be read as one.
How the score is calculated
Stated in full so the calculation can be independently checked, and reproduced by hand if needed.
The radiograph is assigned one of five grades. Grade 0 shows no features of osteoarthritis. Grade 1 shows doubtful joint space narrowing and possible osteophytic lipping. Grade 2 shows definite osteophytes with possible joint space narrowing. Grade 3 shows moderate multiple osteophytes, definite joint space narrowing, some sclerosis and possible bone contour deformity. Grade 4 shows large osteophytes, marked joint space narrowing, severe sclerosis and definite bone contour deformity. Grade 2 or above is the conventional definition of radiographic osteoarthritis.
Instrument profile
- Developer
- J. H. Kellgren and J. S. Lawrence
- Institution
- University of Manchester, United Kingdom
- First published
- 1957
- Items
- 1
- Response format
- Single five-level radiographic grade
- Score range
- 0 to 4
- Direction
- Lower score = better
- Completion time
- About 1 minutes
- Age range
- Adults
- Regions
- Knee, Hip, General Health
- Conditions
- Osteoarthritis, Knee osteoarthritis, Hip osteoarthritis
- Procedures
- Total knee arthroplasty, Total hip arthroplasty, Osteotomy
- Observer agreement
- Interobserver kappa typically 0.5–0.8 depending on joint and observer training
- Validity
- Correlates with cartilage loss and with the probability of progression to arthroplasty, but correlates only weakly with pain and function.
- Reliability
- Reliability is moderate and is weakest at the lower grades, where the distinction between grade 1 and grade 2 turns on the presence of a definite osteophyte. Several distinct written definitions of the grades circulate in the literature, and studies using different definitions are not strictly comparable.
When to use the Kellgren-Lawrence
Well suited to
- Describing radiographic severity of osteoarthritis in the knee or hip in a way that is comparable with the large KL literature.
- Defining eligibility for trials and epidemiological studies, where grade 2 is the usual threshold.
Limitations and poor fits
- As a sole basis for offering arthroplasty — symptoms, function and patient goals matter more than the grade.
- For early or pre-radiographic osteoarthritis, where MRI-based grading is far more sensitive.
- For joints other than the knee and hip without checking that the grade definitions have been validated there.
Kellgren-Lawrence compared with other instruments
Instruments measuring a related construct, with the practical difference between them.
| Instrument | Items | Range | What it adds |
|---|---|---|---|
| Outerbridge | 1 | 0–4 | The Outerbridge classification grades articular cartilage damage from 0 to IV at arthroscopy, progressing from normal cartilage through softening, fissuring under and over 1.3 centimetres in diameter, to full-thickness erosion exposing subchondral bone. |
| KOOS | 42 | 0–100 | The KOOS is a 42-item patient-reported questionnaire that scores knee function as five separate subscales — Symptoms, Pain, Activities of Daily Living, Sport and Recreation, and Quality of Life — each from 0 (extreme problems) to 100 (no problems). |
| HOOS | 40 | 0–100 | The HOOS is a 40-item patient-reported questionnaire that scores hip function as five separate subscales — Symptoms, Pain, Activities of Daily Living, Sport and Recreation, and Hip-related Quality of Life — each from 0 (extreme problems) to 100 (no problems). |
Copyright and permitted use
Published openly because it is the question every clinician and researcher asks before using an instrument, and almost nobody answers it.
A published radiographic grading system. The grade definitions are freely reproducible and no licence is required.
References
- Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Annals of the Rheumatic Diseases. 1957.PMID 13498604
- Schiphof D, Boers M, Bierma-Zeinstra SMA. Differences in descriptions of Kellgren and Lawrence grades of knee osteoarthritis. Annals of the Rheumatic Diseases. 2008.PMID 18718978
- Kohn MD, Sassoon AA, Fernando ND. Classifications in brief: Kellgren-Lawrence classification of osteoarthritis. Clinical Orthopaedics and Related Research. 2016.PMID 26872913
Editorial status
This page has not yet been signed off by a named clinical reviewer. The scoring logic is stated in full above so it can be independently verified, and every threshold is traceable to its source. See our editorial methodology.