Patient outcomes following a total knee arthroplasty (TKA) were traditionally determined by using objective tools like the Knee Society Score (KSS). But the last few years has seen a rise in the use of quality-of-life measures instead, which provide greater emphasis on patient-specific evaluation.

Developed in 1989, The Knee Society Score was originally an objective tool. With shifting trends, in 2011 it was updated and expanded to a mixed outcome measure that’s both objective (physician input) and subjective (patient input). According to its creators, the new score prioritizes the patient perspective to better track patient expectations, satisfaction, and activity levels [3].

As a point of note, the old version of the Knee Society Score doesn’t directly translate to the new 2011 KSS survey, and no conversion algorithm has been developed. This may hinder the ability of researchers to adopt the new KSS while still maintaining their historical/longitudinal original KSS data [1].

The revised score also includes a new pre-operative and post-operative segment. Pre-operatively, patients will be asked questions related to their current symptoms, their knee function, their satisfaction with their pre-op functionality, and their expectations that come with their surgery. The surgeon then completes information on objective measures such as joint alignment, instability, motions and symptoms [2,3].

The new Knee Society Score can be used in conjunction with other outcome measures and has been found to be generally consistent with other knee-specific scores.

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Strengths

The newest version of the Knee Society Score is much improved with an emphasis on the patient perspective. Scores can be generated independently for each category and the tool also provides flexibility and depth to help capture the diverse lifestyles of a younger patient population [1]. The new scoring system has been validated and is broadly applicable across sex, age, activity level, and implant type [1].

 

Weaknesses

Unfortunately, the KSS remains a complicated and clumsy reporting tool to administer. Each interval has different questions and requires both the clinician and the patient to complete an unreasonable amount of data entry within a rigid fashion, which takes much time and effort.

Additionally, leaving a few blank answers might invalidate results as authors of the measure have suggested that it’s not possible to provide a truly valid estimate of the score for any domain that has missing responses [3]. This may result in spending an inordinate amount of time chasing patients and may require much administration.

Overall, the Knee Society Score is a valid and reliable PRO measure that works well in certain situations, such as a prospective study that has a lot of structure and resources devoted to data collection, or for assessing objective and subjective outcomes after total and partial knee arthroplasty. It is not, however, a feasible tool to use as part of an ongoing patient-reported outcomes program.

 

License

A license is required to use the 2011 Knee Society Score. All non-member physicians, academic institutions, and industry representatives should contact the Knee Society to receive more information about licensing.

 

References

  1. Scuderi GR, Bourne RB, Noble PC, Benjamin JB, Lonner JH, Scott WN. The New Knee Society Knee Scoring System. Clinical Orthopaedics and Related Research. 2012;470(1):3-19. doi:10.1007/s11999-011-2135-0. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3237971/
  2. http://www.aaos.org/AAOSNow/2012/Jan/clinical/clinical5/?ssopc=1
  3. Knee Society Scoring system. User manual 2011 http://www.kneesociety.org/web/2011%20kss%20user%20manual_final_12-2012.pdf