KOOS Knee Score

September 06, 2015


The Knee Injury and Osteoarthritis Outcome Score (KOOS)

The Knee Injury and Osteoarthritis Outcome Score (KOOS) is a patient outcome reporting measure widely used for clinical and research purposes. One of the strongest points of the KOOS is that it can be used in both short-term and long-term patient outcome monitoring, which is a very unique feature.

The development of the KOOS was based on the idea that traumatic knee injuries often cause simultaneous damage to multiple structures (ligaments, menisci, cartilage, etc.) which frequently leads to the development of osteoarthritis in later life. In order to follow patients after a trauma and gain insight into their changing symptoms and function over time, a measure was needed to help capture patient outcomes at different intervals, not just in the short or long term. Thus, the KOOS was born.

Prior instruments, such as the Lysholm knee scoring scale, are focused on the short-term outcomes while instruments such as WOMAC focus on long term results. The KOOS helps to bridge this gap and it can be used for follow-up of both sets of patients – those who require monitoring for acute injury and those who require it for chronic ongoing conditions.

Scoring the KOOS is straightforward. The questionnaire holds five (5) separately scored subscales: pain, function in daily living, function in sport and recreation, other symptoms and knee-related quality of life. Each question is assigned a score (0-4) and a normalized score is calculated for each subscale. The KOOS is scored on a 0-100 scale, with 100 indicating no symptoms and 0 indicating extreme symptoms. The KOOS may be scored manually or via a KOOS Excel scoring file.


The main advantage of the KOOS is its widespread use in both research and clinical settings. Additionally, because this measure was predicated on the WOMAC survey and contains many of the same questions, a WOMAC score can be calculated from the KOOS questionnaire.

The ability to use the KOOS for both short and long-term outcome reporting means it can be used to assess changes from week to week that are induced by treatments (ie. medication, operation, physical therapy, etc.) or over years following a primary injury or osteoarthritis. This is a key advantage of this PRO measure.


From a practical standpoint, the KOOS survey presents some challenges. It is much longer than other questionnaires and takes patients a considerable amount of time to complete. The scoring system is quite complicated and can be very labor and time consuming when compared to other measures.

If this can be overlooked, the KOOS questionnaire is an excellent measure that has quickly become the instrument of choice for the total knee replacement patient population. In addition to gaining popularity in the orthopedic surgery community, the KOOS survey is being recognized by insurance companies as a way to evaluate indications for joint replacement candidates and to quantify the success of total knee replacement outcomes.


Free. The KOOS measure does not require a license and is free of charge. To learn more, please visit their website: www.koos.nu/.

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