Patient-reported outcome measure
IKDC
International Knee Documentation Committee Subjective Knee Evaluation Form
The 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.
This instrument is not reproduced here
The IKDC Subjective Knee Evaluation Form is copyright the American Orthopaedic Society for Sports Medicine. Permission is required to reproduce or distribute it, and although it is commonly granted for non-commercial clinical and academic use on request, it is not granted by default and is not open content. We have not sought permission, so the items are not reproduced here and no calculator is offered. Request the form and its scoring key from the AOSSM.
Obtain a licence from the rights holderWhat the IKDC score means
IKDC scores run from 0 to 100, where a higher score is better. The bands below are conventional reporting categories, not diagnostic cut-offs.
- Severe limitation0–29.9
Descriptive groupings only. The developers defined no severity categories — the IKDC is designed to be read against the patient’s own baseline and against age- and sex-matched normative values, not against fixed bands.
- Marked limitation30–49.9
- Moderate limitation50–69.9
- Mild limitation70–89.9
- Minimal limitation90–100
How the score is calculated
Stated in full so the calculation can be independently checked, and reproduced by hand if needed.
Each of the eighteen scored items carries an ordinal response set, and the response sets differ between items — this is not a questionnaire in which every item is scored on the same scale. The responses are summed to a raw total, and that raw total is then transformed onto a 0 to 100 scale by subtracting the lowest possible raw total, dividing by the range of possible raw totals, and multiplying by 100. A score of 100 means no symptoms and no limitation of activity; a lower score means greater symptoms and greater limitation, so the direction is the same as the Lysholm and the opposite of the Oswestry. One item on the form — the patient’s rating of knee function BEFORE the injury — is recorded for context and is not part of the score. The transformation above is the published scoring rule; the per-item response weighting is set out in the scoring key supplied with the licensed form, and is deliberately not reproduced or approximated here.
Missing data
The developers’ rule is that the score may be computed when at least 90% of the items are answered — that is, with no more than two items missing — by dividing the raw total by the number of items actually answered and transforming as usual. With three or more items missing the form is not scored. Confirm this against the scoring key supplied with your copy before applying it to study data.
Instrument profile
- Developer
- James J. Irrgang, Allen F. Anderson and the International Knee Documentation Committee
- Institution
- University of Pittsburgh and the American Orthopaedic Society for Sports Medicine, United States
- First published
- 2001
- Custodian
- American Orthopaedic Society for Sports Medicine (AOSSM)
- Items
- 18
- Response format
- Mixed ordinal response scales, item-specific
- Score range
- 0 to 100
- Direction
- Higher score = better
- Recall period
- The last four weeks
- Completion time
- About 10 minutes
- Age range
- Adolescents and adults
- Regions
- Knee
- Conditions
- Anterior cruciate ligament tear, Meniscal tear, Articular cartilage defect of the knee, Patellofemoral pain, Knee osteoarthritis, Knee instability
- Procedures
- Anterior cruciate ligament reconstruction, Meniscal repair, Partial meniscectomy, Cartilage repair of the knee
- Languages
- English, German, Dutch, French, Italian, Spanish, Swedish, Norwegian, Danish, Turkish, Persian, Chinese, Japanese, Korean, Brazilian Portuguese
- Test–retest (ICC)
- Consistently reported around 0.9 over intervals of one to two weeks in stable patients
- Internal consistency
- Cronbach’s alpha around 0.9, consistent with a single underlying construct
- Validity
- Correlates strongly with the KOOS, the Lysholm and the physical component of the SF-36 across ligament, meniscal and cartilage pathology. Age- and sex-stratified normative values were published for it, which is unusual among knee measures and lets an individual score be expressed as a percentile rather than only as a raw number.
- Responsiveness
- Among the more responsive knee measures after ligament reconstruction and cartilage surgery. Published minimal clinically important difference estimates vary with the population and the anchor used, and we have not verified a single figure well enough to quote it — take the threshold from a study whose population matches yours.
- Ceiling effect
- Present in young athletes who return to full sport, who cluster in the 90s.
- Floor effect
- Uncommon.
Normative values
Reference values from published cohorts, for comparison against the score you calculated.
| Population | Age | Mean | SD |
|---|---|---|---|
| Healthy knees, United States population sample — the reference values the developers published alongside the form | — | Declines with age; young adults score close to 100, older adults lower | — |
| Patients before anterior cruciate ligament reconstruction | — | Commonly in the 40s to 50s | — |
When to use the IKDC
Well suited to
- Anterior cruciate ligament, meniscal and cartilage outcome reporting, where the IKDC is the expected measure in the sports medicine literature.
- When an individual score should be interpreted against age- and sex-matched normative values rather than against a band label.
- Following a single patient through rehabilitation, where a general knee measure rather than a condition-specific subscale structure is wanted.
Limitations and poor fits
- Without permission from the rights holder — the form is copyright and permission is not granted by default.
- Knee osteoarthritis in older patients, where the KOOS or the WOMAC map better onto the symptoms that matter and the IKDC’s sport items floor out.
- When separate symptom, pain, function and quality-of-life subscales are needed: the IKDC produces one total, whereas the KOOS produces five subscales that move independently.
- Detecting further improvement in an athlete already scoring in the 90s.
IKDC compared with other instruments
Instruments measuring a related construct, with the practical difference between them.
| Instrument | Items | Range | What it adds |
|---|---|---|---|
| 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). |
| Lysholm | 8 | 0–100 | The Lysholm Knee Scoring Scale is an eight-domain questionnaire that rates knee symptoms and function — limp, support, locking, instability, pain, swelling, stair climbing and squatting — on a 0 to 100 scale, where 95 and above is graded excellent, 84 to 94 good, 65 to 83 fair, and below 65 poor. |
| Tegner | 1 | 0–10 | The Tegner Activity Scale is a single-item ordinal ladder that grades a patient's work and sport activity from 0 (sick leave or disability pension because of knee problems) to 10 (national or international elite competitive sport), and is normally recorded twice — the pre-injury level and the current level — so that the drop between them can be reported. |
| Marx | 4 | 0–16 | The Marx Activity Rating Scale measures how frequently a patient runs, cuts, decelerates and pivots in their healthiest state over the past year, scoring each on a 0 to 4 frequency scale for a total of 0 to 16, where a higher score means a more demanding activity level. |
| QuickDASH | 11 | 0–100 | The QuickDASH is an 11-item shortened form of the DASH that measures physical function and symptoms across the whole upper limb on a single 0 to 100 scale, where a higher score means greater disability. |
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.
The IKDC Subjective Knee Evaluation Form is copyright the American Orthopaedic Society for Sports Medicine. Permission is required to reproduce or distribute it, and although it is commonly granted for non-commercial clinical and academic use on request, it is not granted by default and is not open content. We have not sought permission, so the items are not reproduced here and no calculator is offered. Request the form and its scoring key from the AOSSM.
Rights holder’s own pageReferences
- Irrgang JJ, Anderson AF, Boland AL, Harner CD, Kurosaka M, Neyret P, Richmond JC, Shelborne KD. Development and validation of the International Knee Documentation Committee subjective knee form. American Journal of Sports Medicine. 2001.
- Irrgang JJ, Anderson AF, Boland AL, et al.. Responsiveness of the International Knee Documentation Committee Subjective Knee Form. American Journal of Sports Medicine. 2006.
- Anderson AF, Irrgang JJ, Kocher MS, Mann BJ, Harrast JJ. The International Knee Documentation Committee Subjective Knee Evaluation Form: normative data. American Journal of Sports Medicine. 2006.
- Collins NJ, Misra D, Felson DT, Crossley KM, Roos EM. Measures of knee function: a review of patient-reported outcome instruments. Arthritis Care and Research. 2011.
Editorial status
Not yet reviewedQueued for clinical review by Sam Tuffun, PT, DPT. Sign-off has not taken place — this is a placeholder assignment, not a completed review.