KOOS Knee Score

Knee PRO Tools Guide

The Knee Injury and Osteoarthritis Outcome Score (KOOS)

The Knee Injury and Osteoarthritis Outcome Score (KOOS) is a widely used patient-reported outcome measure (PROM) for research purposes in experimental studies and large-scale databases. One of the strongest points of KOOS is that it can be used for both short-term and long-term patient outcome monitoring, which makes it a very unique tool.

The development of 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 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, KOOS was born.

Other tools are focused on short-term outcomes, like the Lysholm Knee Scoring System, while tools like WOMAC are focused on the long-term. KOOS bridges this gap and it can be used for follow-up of both sets of patients: those that require monitoring for acute injury and those that require it for chronic ongoing conditions.

Scoring of the KOOS is easy to follow. The questionnaire has five separately scored subscales: Pain, Function in Daily Living (ADL), Function in Sport and Recreation, Other Symptoms, and Knee-Related Quality of Life (QOL). Each question is assigned a score (0-4) and a normalized score is calculated for each subscale (100 indicates no symptoms and 0 indicates extreme symptoms). The KOOS may be scored manually or via a KOOS Excel scoring file.

The KOOS has been validated for several orthopedic interventions such as Anterior Cruciate Ligament Reconstruction, Meniscectomy, and Total Knee Replacement [3].


The main advantage of the KOOS PROM 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.

A key advantage of this PRO measure specifically is the ability to use KOOS for both short and long-term outcome reporting. This 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.


From a practical standpoint, the KOOS survey presents some challenges. It’s much longer than other questionnaires and takes patients a considerable amount of time to fill out. In addition, compared to other tools the scoring system is quite complicated and can be very labor intensive and time-consuming. If this can be overlooked, the KOOS questionnaire is an excellent tool that’s quickly becoming the instrument of choice for the total knee replacement patient population.

In addition to gaining popularity in the orthopedic surgery community, KOOS is now 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.

Recently, a shortened version of the KOOS measure was validated, called the KOOS, JR.


The KOOS Measure does not require a license and is free to use.


  1. Roos, E. M., & Lohmander, L. S. (2003). The Knee injury and Osteoarthritis Outcome Score (KOOS): from joint injury to osteoarthritis. Health and quality of life outcomes, 1(1), 64. https://hqlo.biomedcentral.com/articles/10.1186/1477-7525-1-64
  2. Roos, E. M., & Lohmander, L. S. (2003). The Knee injury and Osteoarthritis Outcome Score (KOOS): from joint injury to osteoarthritis. Health and Quality of Life Outcomes, 1, 64. http://doi.org/10.1186/1477-7525-1-64 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC280702/

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