Knee Injury and Osteoarthritis Outcome Score
Also known as: KOOS, KOOS Scale
The Knee Injury and Osteoarthritis Outcome Score (KOOS) is a patient-reported outcome measure designed for active patients with knee injury and osteoarthritis. Developed by Roos and colleagues in 1998, KOOS extends assessment beyond traditional osteoarthritis scales to include symptoms, pain, function in daily living, function in sport and recreation, and knee-related quality of life—making it ideal for younger, more active populations.
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When to use it
KOOS is the standard measure for active patients with knee injury or mild-to-moderate knee osteoarthritis in sports medicine, orthopedic surgery, and rehabilitation. Use at baseline to establish functional status, during rehabilitation to track progress in specific domains, and post-intervention (surgery or conservative therapy) to quantify outcome. KOOS is particularly valuable in younger populations, athletes, and those with post-traumatic knee dysfunction.
Strengths & limitations
- Comprehensive multidimensional assessment captures pain, symptoms, function, sports participation, and quality of life in five distinct domains.
- Specifically designed for active patients and younger populations; highly responsive to change in sports and recreational function unlike generic osteoarthritis scales.
- Available in 60+ languages with strong international validation; considered the gold standard in knee injury and early osteoarthritis research.
- Subscale structure enables identification of specific functional deficits and targeting of rehabilitation interventions (e.g., addressing pain vs. sport limitation separately).
- Designed for knee conditions; not applicable to other joint disorders or generalized functional assessment.
- Length (42 items) is longer than abbreviated versions like WOMAC; may increase patient burden in busy clinical settings.
- Self-report measure; subject to recall bias and psychological factors that may influence perception of disability.
- Quality of life subscale (4 items) is relatively brief and may not capture broader psychosocial impacts.
Frequently asked
How do I interpret the five KOOS subscales?
Report each subscale (pain, symptoms, ADL, sport/recreation, QOL) separately with its own 0–100 score. Pain subscale reflects symptom severity; ADL reflects function in walking, stairs, kneeling; sport/recreation reflects ability to participate in sports; QOL reflects overall knee-related impact. An athlete might have low pain but low sport/recreation scores, indicating persistent limitations.
What is the difference between KOOS and WOMAC?
WOMAC focuses on pain, stiffness, and function in older patients with osteoarthritis. KOOS expands to include sport/recreation and quality of life, making it better suited for younger, active patients. WOMAC has 24 items; KOOS has 42 items. Use WOMAC for older populations and KOOS for younger patients or athletes.
What is a clinically meaningful change in KOOS subscale scores?
A change of 8–10 points on any KOOS subscale (0–100 scale) represents a minimally clinically important difference. Meaningful improvement in sport/recreation may require larger change (12–15 points) given the competitive demands. Contextualize change with patient-reported global impression of change.
How often should KOOS be administered during rehabilitation?
Baseline, 6 weeks, 12 weeks, and 6 months are standard assessment intervals. More frequent measurement (weekly) adds little value, as true change in function and sport participation requires adequate time for tissue healing and rehabilitation. Adjust intervals based on the intervention (surgery vs. conservative care).
Sources
- Roos, E. M., Roos, B. P., Lohmander, L. S., Ekdahl, C., & Beynnon, B. D. (1998). Knee Injury and Osteoarthritis Outcome Score (KOOS): development of a self-administered outcome measure. Journal of Orthopaedic & Sports Physical Therapy, 28(2), 88–96. DOI: 10.2519/jospt.1998.28.2.88 ↗
- Roos, E. M., & Toksvig-Larsen, S. (2003). Knee injury and Osteoarthritis Outcome Score (KOOS): validation and comparison in total meniscectomy versus meniscus preservation surgery for degenerative meniscus tears. Osteoarthritis and Cartilage, 11(5), 330–337. link ↗
How to cite this page
ScholarGate. (2026, June 3). Knee Injury and Osteoarthritis Outcome Score. ScholarGate. https://scholargate.app/en/rehabilitation/koos
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- Hip Disability and Osteoarthritis Outcome ScoreRehabilitation↔ compare
- WOMAC Osteoarthritis IndexRehabilitation↔ compare