Knee
Knee osteoarthritis
Knee osteoarthritis is assessed with a radiographic grade for structural severity and a patient-reported outcome measure for symptoms and function, and the two correlate only weakly — which is why both are needed.
What you are actually deciding
Use a radiographic grade to describe structure and a PROM to describe the patient. A patient with grade 4 changes may be minimally symptomatic, and a patient with grade 1 may be severely limited, so neither measure substitutes for the other when deciding on arthroplasty.
Patient-reported outcome measure7
- IKDC Calculator18 itemsInternational Knee Documentation Committee Subjective Knee Evaluation FormThe IKDC Subjective Knee Evaluation Form is an 18-item patient-reported questionnaire covering knee symptoms, sports and daily activity and current knee function, whose raw total is transformed to a 0 to 100 score where 100 means no symptoms and no activity limitation — it requires permission from the AOSSM, so the items are not reproduced here.
- KOOS Calculator42 itemsKnee injury and Osteoarthritis Outcome ScoreThe 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).
- Knee Outcome Survey Calculator25 itemsKnee Outcome Survey — Activities of Daily Living Scale and Sports Activity ScaleThe Knee Outcome Survey is a patient-reported measure of knee function with two scales — a 14-item Activities of Daily Living Scale and an 11-item Sports Activity Scale — each item scored 5 to 0 and expressed as a percentage of the maximum, so that 100% means no symptoms and no functional limitation.
- LEFS Calculator20 itemsLower Extremity Functional ScaleThe LEFS is a 20-item patient-reported questionnaire that measures difficulty with everyday lower limb activities on a single 0 to 80 scale, where 80 indicates no difficulty and a change of 9 points is the smallest difference patients reliably notice.
- PROMIS Global-10 Calculator10 itemsPROMIS Global Health Short Form (Global-10)The PROMIS Global-10 is a 10-item general health questionnaire that yields two four-item summary scores — Global Physical Health and Global Mental Health — each reported as a T-score calibrated to the United States general population, where 50 is the population mean, 10 points is one standard deviation, and higher scores indicate better health.
- Tampa Scale of Kinesiophobia Calculator17 itemsTampa Scale of KinesiophobiaThe Tampa Scale of Kinesiophobia is a 17-item self-report questionnaire of fear of movement and (re)injury in people with pain, scored 1 to 4 per item (four items reverse-scored) for a total of 17 to 68, where a higher total means more fear and a total above 37 is widely used as the cut-off for high kinesiophobia.
- TSK-11 Calculator11 itemsTampa Scale of Kinesiophobia, 11-item versionThe TSK-11 is the 11-item short form of the Tampa Scale of Kinesiophobia, which drops the four reverse-scored items and items 9 and 14 of the original, scores each remaining statement 1 to 4 for a total of 11 to 44, and reads a higher total as more fear of movement and (re)injury.
Clinical calculator1
Classification system2
- Kellgren-Lawrence Classification1 itemsKellgren-Lawrence Classification of OsteoarthritisThe 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.
- Outerbridge Classification1 itemsOuterbridge Classification of Chondral LesionsThe 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.
Thresholds that apply here
Published change thresholds across the instruments above. Check the population matches your patient before using a value — a threshold derived in a different cohort will mislead you.
| Instrument | Type | Value | Subscale | Population |
|---|---|---|---|---|
| KOOS | MCID | 8–10 points | Pain | Total knee arthroplasty |
| KOOS | MCID | 8–10 points | ADL | Total knee arthroplasty |
| KOOS | MCID | 10 points | All subscales | ACL reconstruction |
| KOOS | PASS | ~78 points | Pain | Knee arthroplasty |
| KOOS | PASS | ~63 points | QOL | Knee arthroplasty |
| KOOS | MDC | 6–12 points | Varies by subscale | Knee osteoarthritis |
| LEFS | MCID | 9 points | — | Adults with lower limb musculoskeletal dysfunction |
| LEFS | MDC | 9 points (90% confidence) | — | Adults with lower limb musculoskeletal dysfunction |
| LEFS | MCID | 9 points | — | Knee osteoarthritis and post-arthroplasty |
See the full threshold database for every instrument on the site.