The Knee injury and Osteoarthritis Outcome Score (KOOS): from joint injury to osteoarthritis

Abstract

The Knee injury and Osteoarthritis Outcome Score (KOOS) was developed as an extension of the WOMAC Osteoarthritis Index with the purpose of evaluating short-term and long-term symptoms and function in subjects with knee injury and osteoarthritis. The KOOS holds five separately scored subscales: Pain, other Symptoms, Function in daily living (ADL), Function in Sport and Recreation (Sport/Rec), and knee-related Quality of Life (QOL). The KOOS has been validated for several orthopaedic interventions such as anterior cruciate ligament reconstruction, meniscectomy and total knee replacement. In addition the instrument has been used to evaluate physical therapy, nutritional supplementation and glucosamine supplementation. The effect size is generally largest for the subscale QOL followed by the subscale Pain. The KOOS is a valid, reliable and responsive self-administered instrument that can be used for short-term and long-term follow-up of several types of knee injury including osteoarthritis. The measure is relatively new and further use of the instrument will add knowledge and suggest areas that need to be further explored and improved.

Figure 1

Development and evaluation of the KOOS.

Figure 2

Effect sizes of KOOS, WOMAC and SF-36 six months after ACL-reconstruction. Comparison of effect sizes of KOOS, WOMAC and SF-36 six months after surgical reconstruction of the ruptured anterior cruciate ligament. Effect size was defined as mean score change divided by the pre-operative standard deviation. The data are previously published (n = 21, mean age 32 years) [5]. Placebo or sham treatment results have not been subtracted to generate effect sizes. It should be noted that the effect size displayed here will be influenced by the preoperative within-group variation of the score dimension measured.

Figure 3

Effect size for different surgical interventions measured by KOOS. KOOS effect sizes 6 months following surgical knee interventions. Effect size was defined as mean score change divided by the pre-operative standard deviation. The data from total knee replacement [8] (n = 105, mean age 71.3 years) and anterior cruciate ligament reconstruction [5] (n = 21, mean age 32 years) are previously published. The data from tibial osteotomy concerns 50 patients (mean age 54 years) undergoing hemicallotasis osteotomy (W-Dahl A, Lund University, personal communication 2001). The data from cartilage repair concerns 50 patients (mean age 34 years) undergoing autologus cartilage transplant (Olsson M, University of Gothenburg, personal communication 2002). The data for meniscectomy concern 66 patients (mean age 44 years) undergoing arthroscopic partial meniscectomy (Roos E, Lund University, personal communication 2003). Placebo or sham treatment results have not been subtracted to generate effect sizes. It should be noted that the effect size displayed here will be influenced by the preoperative within-group variation of the score dimension measured. This may vary between the different study groups. All data are published with permission from the authors.