Knee Society Score
Score pain, range of motion, stability, deductions, walking, stairs and walking aids to get the Knee Society knee score and function score (0–100 each), with the rating band and a comparison with the 2011 KSS. Educational only — not medical advice.
The original Knee Society Score (Insall et al., 1989) gives two separate scores out of 100.
Use the Knee Society Score
Original 1989 Knee Society Score — educational, not medical advice
Use clinician-assessed categories from the historical record. The current 2011 Knee Society Score is a different, copyrighted four-subscale instrument. Obtain its official forms and permissions from The Knee Society. This page is educational and is not medical advice, a diagnosis or a treatment recommendation.
Version and interpretation
The 1989 publication introduced separate knee and function scores so general infirmity would not lower the knee assessment. Compare scores only under a defined clinical or research protocol; this page does not assign a universal severity grade. Scores below 0 are displayed as 0.
Original Knee Society Score — item weights (Insall 1989)
Maximum 100 points for each score. If the deductions make a score negative, it is recorded as 0.
| Score | Item | Points by finding | Max |
|---|---|---|---|
| Knee score | Pain | None 50 · mild or occasional 45 · stairs only 40 · walking and stairs 30 · moderate occasional 20 · moderate continual 10 · severe 0 | 50 |
| Knee score | Range of motion | 1 point per 5° of motion | 25 |
| Knee score | Stability — anteroposterior | < 5 mm 10 · 5–10 mm 5 · > 10 mm 0 | 10 |
| Knee score | Stability — mediolateral | < 5° 15 · 6–9° 10 · 10–14° 5 · ≥ 15° 0 | 15 |
| Knee score | Flexion contracture | 5–10° −2 · 11–15° −5 · 16–20° −10 · > 20° −15 | −15 |
| Knee score | Extension lag | < 10° −5 · 10–20° −10 · > 20° −15 | −15 |
| Knee score | Alignment | 5–10° valgus 0 · 0–4° or 11–15° valgus −3 per degree · other −20 | −20 |
| Function score | Walking | Unlimited 50 · > 10 blocks 40 · 5–10 blocks 30 · < 5 blocks 20 · housebound 10 · unable 0 | 50 |
| Function score | Stairs | Normal up and down 50 · normal up, down with rail 40 · up and down with rail 30 · up with rail, unable down 15 · unable 0 | 50 |
| Function score | Walking aid | Cane −5 · two canes −10 · crutches or walker −20 | −20 |
Rating bands used in many studies (not part of the 1989 paper): excellent 80–100, good 70–79, fair 60–69, poor below 60.
1989 Knee Society Score vs the 2011 KSS
The 2011 Knee Society Score keeps a surgeon-rated knee score and adds patient-reported scales. Structure from the Knee Society's 2011 KSS licensed user manual and Scuderi et al. (2012); the questionnaire items themselves are not reproduced here.
| Part | 1989 KSS (Insall) | 2011 KSS |
|---|---|---|
| Who completes it | Surgeon (both scores) | Surgeon (objective knee score) and patient (all other parts) |
| Knee / objective knee score | 100: pain 50, motion 25, stability 25, minus deductions | 100 (7 items): alignment 25, instability 25, joint motion 25 (more above 125°), symptoms 25 rated by the patient, minus deductions |
| Function | 100: walking 50, stairs 50, minus walking aid | 100 (19 items): walking and standing 30, standard activities 30, advanced activities 25, discretionary activities 15 |
| Patient satisfaction | — | 40 (5 items) |
| Patient expectations | — | 15 (3 items) |
| Reporting | Knee and function scores reported separately | Function, satisfaction and expectation reported as separate scores; not numerically related to the 1989 score |
| Access | Published in Clin Orthop Relat Res 1989 | Copyrighted; forms licensed by The Knee Society |
Not medical advice. Scores support, and do not replace, clinical assessment.
Quick answer
The original Knee Society Score (Insall et al., 1989) gives two separate scores out of 100. The knee score adds pain (50 points), range of motion (1 point per 5°, maximum 25) and stability (25: anteroposterior 10, mediolateral 15), then subtracts deductions for flexion contracture (up to 15), extension lag (up to 15) and malalignment (up to 20). The function score adds walking distance (50) and stair climbing (50) and subtracts 5 for a cane, 10 for two canes and 20 for crutches or a walker. Many studies grade each score 80–100 excellent, 70–79 good, 60–69 fair and below 60 poor. The 2011 KSS is a different, licensed instrument: an objective knee score (100), patient satisfaction (40), expectations (15) and functional activities (100), reported separately.
Examples
| Item (1989 KSS) | Finding | Points |
|---|---|---|
| Pain | Mild or occasional | 45 |
| Range of motion | 110° (1 point per 5°) | 22 |
| Stability | AP < 5 mm, ML 6–9° | 10 + 10 |
| Deductions | Flexion contracture 5–10°, alignment 3° valgus | −2 − 6 |
| Knee score | 45 + 22 + 20 − 8 | 79 (good) |
| Function score | > 10 blocks (40) + stairs with rail (30) − cane (5) | 65 (fair) |
Select each finding to get the knee and function scores; this is an educational calculator, not medical advice.
Summary
The Knee Society Clinical Rating System (Insall et al., Clin Orthop Relat Res 1989) rates a replaced knee with two separate 100-point scores: a knee score for pain, motion, stability and deformity, and a function score for walking, stairs and walking aids. This calculator applies the published item weights and deductions, shows the commonly used rating bands, and compares the original system with the 2011 Knee Society Score, which adds patient-reported satisfaction, expectations and a 19-item functional activity scale. It is an educational tool and does not diagnose or recommend treatment.
How it works
- Select the pain level (0–50 points) and enter the range of motion in degrees (1 point per 5°, up to 25).
- Select mediolateral (up to 15) and anteroposterior (up to 10) stability.
- Add deductions for flexion contracture, extension lag and alignment (5–10° valgus scores no deduction).
- Select walking distance, stair climbing and any walking aid for the function score.
- Read the knee score and function score (0–100 each, never added together in the original system) with the commonly used rating band.
Use cases
- Orthopedic teams recording pre- and post-operative scores after total knee arthroplasty.
- Researchers extracting or comparing original KSS knee and function scores from older studies.
- Physical therapists tracking walking and stair function after knee replacement.
- Students learning how the 1989 Knee Society Clinical Rating System is weighted.
- Checking how a published 2011 KSS differs from the original score before comparing studies.