Oxford Knee Score Calculator
Validated 12-Item PRO for TKA (OKS)
Patient-Reported Outcomes
12 validated questions for TKA assessment
Score Summary
Current Total48
Max Score48
Questions12 / 12
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
Pre-operative baseline assessment before total knee arthroplasty (TKA)
Post-operative outcome measurement following TKA at 6 months, 1 year, and annually
Monitoring functional recovery during rehabilitation after knee replacement
Clinical trials evaluating TKA implant designs, surgical approaches, or rehabilitation protocols
Patient-reported outcome measure (PROM) for national joint registry submissions
Patient Population
Designed for patients undergoing primary or revision total knee arthroplasty. Validated for osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis.
How it Works
Scoring
Total Score = Sum of 12 item scores (each 0-4) = 0 to 48
Each question has 5 ordinal response options scored 0 (worst) to 4 (best)
The original OKS used a 12-60 scale; the 0-48 system is now standard
Higher scores indicate better knee function and less pain
Domains Covered
| Domain | Questions | Score Range |
|---|---|---|
| Pain | 1, 5, 6, 9, 10 | 0-20 |
| Function | 2, 3, 4, 7, 8, 11, 12 | 0-28 |
Clinical Pearls
Interpretation Guide
| Score Range | Classification | Clinical Implication |
|---|---|---|
| 40 – 48 | Satisfactory Joint Function | Excellent outcome; meets patient expectations |
| 30 – 39 | Mild to Moderate Arthritis | Some limitations in higher-demand activities |
| 20 – 29 | Moderate to Severe Arthritis | Notable functional impairment |
| 0 – 19 | Severe Arthritis | Consider revision or pain management consult |
Key Considerations
The OKS is a joint-specific rather than disease-specific tool — best for TKA outcomes
Minimal Clinically Important Difference (MCID): 5 points
Minimal Detectable Change (MDC): 7 points at 95% confidence
Pre-operative score is the strongest predictor of post-operative OKS at 1 year
Patient expectations significantly influence satisfaction independent of OKS
Common Pitfalls
Do not use the 12-60 scoring system without clearly documenting the scale used
Ensure patients complete the questionnaire independently without clinician influence
Missing data: if 2 or fewer items are missing, impute using mean of remaining items
Next Steps
Clinical Actions
01
Interpret score using validated classification thresholds
02
Compare score to pre-operative baseline to quantify surgical improvement
03
A score < 30 at 1 year post-TKA warrants investigation: infection, loosening, instability
04
Trend scores annually — a decline of ≥ 5 points merits clinical assessment
05
Correlate with objective measures: range of motion, stability, radiographic alignment
06
Include in joint registry submissions for national benchmarking
The Evidence
Primary Reference
Questionnaire on the perceptions of patients about total knee replacement
Dawson J et al. • Journal of Bone and Joint Surgery (British). 1998;80(1):63-69 — Original development and validation of the Oxford Knee Score
Psychometric Properties
Test-retest reliability: ICC > 0.90
Internal consistency: Cronbach's alpha 0.85-0.95
MCID: 5 points (range 4-8 depending on population)
Effect size at 1 year post-TKA: 2.5-3.5 (very large)
Correlation with SF-36 physical function: r = 0.60-0.70
Origins & History
Historical Background
The Oxford Knee Score was developed in 1998 by Dawson, Fitzpatrick, Murray, and Carr at the University of Oxford, UK. It was designed specifically to assess patient perceptions of outcomes after total knee replacement, filling a gap in condition-specific PROMs for knee arthroplasty.
Last Comprehensive Review: 2026-07-17