The IKDC Subjective Knee Form is a knee-specific PROM used across a wide range of knee conditions. This page explains what the IKDC is, what it measures, the items it contains, how it is scored, and how it is used.
What is the IKDC?
The IKDC (International Knee Documentation Committee) Subjective Knee Evaluation Form is a self-reported questionnaire that measures symptoms, function, and sports activity in people with a variety of knee conditions. It was developed by the International Knee Documentation Committee and validated by Irrgang and colleagues, and it is used as a standard form for reporting outcomes of knee conditions including ligament injuries, meniscal and cartilage problems, and osteoarthritis.
What does the IKDC measure?
The IKDC assesses three domains within a single overall score: symptoms (including pain, stiffness, swelling, and giving-way), sports and daily activities, and current knee function. It is designed to reflect how the knee affects the patient across everyday and athletic tasks.
What questions are included in the IKDC?
The form contains 18 items covering the three domains. Symptom items address the highest activity level possible without significant pain or swelling, and the frequency and severity of pain, stiffness, swelling, locking, and instability. Activity items address the ability to perform tasks such as going up and down stairs, kneeling, squatting, sitting, rising from a chair, running, jumping, and stopping and starting. A function item asks patients to rate current knee function compared with function before the knee problem; the "function prior to injury" item is not counted in the total.
How is the IKDC scored?
Each item is scored on an ordinal scale, and item scores are summed (excluding the "function prior to injury" item). The raw sum is divided by the maximum possible score of 87 and multiplied by 100 to transform it to a 0-to-100 scale. Higher scores indicate better function and fewer symptoms, with 100 meaning no limitation in daily or sporting activities and no symptoms. A score can be calculated when at least 90% of items (16 of 18) are answered.
How is the IKDC used in clinical practice?
The IKDC is widely used to track knee outcomes before and after treatment, particularly after ligament reconstruction such as ACL surgery, and to compare results across studies. Normative data stratified by age and sex are available, which helps clinicians interpret an individual score relative to the general population.
Strengths and limitations
The IKDC's strengths include broad applicability across knee diagnoses, a single interpretable score, available normative data, and strong evidence of reliability, validity, and responsiveness. Its limitations include reduced sensitivity in specific sub-populations compared with targeted subscale measures like the KOOS, and the fact that some items are reverse-scored, which requires careful scoring.
Frequently asked questions
How many questions are on the IKDC? There are 18 items; 17 contribute to the score (the "function prior to injury" item is excluded).
What is a good IKDC score? Scores range from 0 to 100, and higher is better; 100 indicates no symptoms and no activity limitation.
What conditions is the IKDC used for? It is used across many knee conditions, including ligament injuries, meniscal and cartilage problems, and osteoarthritis.
References
- Irrgang JJ, Anderson AF, Boland AL, et al. Development and validation of the International Knee Documentation Committee Subjective Knee Form. American Journal of Sports Medicine. 2001;29(5):600-613.
- Anderson AF, Irrgang JJ, Kocher MS, Mann BJ, Harrast JJ. The IKDC Subjective Knee Evaluation Form: normative data. American Journal of Sports Medicine. 2006;34(1):128-135.
- Collins NJ, Misra D, Felson DT, Crossley KM, Roos EM. Measures of knee function. Arthritis Care & Research. 2011;63(S11):S208-S228.
