1. ‘The Forgotten Joint Score’ Construct Validity and Test-Retest Reliability
Justin Roe, Justin Webb, Lucy Salmon
North Sydney Orthopaedic & Sports Medicine Centre
Mater Hospital, Sydney, Australia

2. Disclosures Educational support from Smith and Nephew Stryker
Funding for this study was received from Stryker Inc.
Associate Professor Justin Roe

3. Introduction 51,212 Total Knee Replacements in Australia 2013*
Results generally good
10-15% patients dissatisfied **
Review of outcomes is important
Patient reported outcome measures (PROMS)
In 2013 over knee replacements were implanted in Australia. The results of these procedures are generally very good however 10-15% of patients remain dissatisfied with the outcome.
It is therefore important to continue to review these outcomes.
Patient derived outcome scores have become the method of choice with recognition of the gap between clinician and patient perception of success
* ANJRR 2014
** Becker Knee Surg Sports Traumatol Arthrosc 2011, Kim J Arthroplasty 2009

4. What makes a good outcome score?
Measure the outcome in question
Reliable
Reproducible
Responsive
Validated
Easy to administer
When considering an outcome score it must be able to measure the desired outcome in question. It must also be reliable, reproducible, responsive to changes in condition state and be validated. It should also ideally be easy to administer
Associate Professor Justin Roe

5. Why a new score? Many validated scores currently available
KOOS, WOMAC, IKS, Oxford
Pain, function and symptoms variables
Excellent improvement in scores
The Ceiling Effect
Large percentage responses near perfect
Inability to detect further improvement
Up to 20% in WOMAC
With many validated scores such as the KOOS and WOMAC currently available for use in assessing TKR outcomes why do we need another score. These scores tend to concentrate on pain, function relating to ADL’s and general symptoms. The majority of studies have shown marked improvement of function often with means of close to 90% of maximum.
With these excellent results The concept of the ceiling effect has become increasingly relevent. The ceiling effect occurs when a large portion of patients score near perfect results. This may reflect an inability to detect change in function and further improvement beyond this level
Associate Professor Justin Roe

6. The Forgotten Joint Score
Newly developed and Validated in German Language
Patient awareness of TKR
The ‘Forgotten Joint’ is a successful TKR
The forgotten joint score is a recently developed outcome tool that has been validated in it’s german language form.
It consists of 12 questions with patients asked to rate their awareness of their TKR during various activities from never to mostly.
The concept of this scoring system is that the ‘forgotten joint’ replacement is a truly successfully procedure.
Associate Professor Justin Roe

7. The Forgotten Joint Score (FJS-12)
These are the questions of the FJS.
Responses are scored from 0-4 with no awareness scoring 0.
The average score out of 4 is determined and multiplied by 25 to get a score out of 100. This is then subtracted from 100 so that a perfect score is 100.

8. Methods 240 Consecutive TKR patients enrolled
Patients completed KOOS and FJS-12
FJS-12 repeated at 4 weeks
Test-retest reliability was analysed calculating a Intraclass Correlation Coefficient
Convergent construct validity was assessed with a Spearman’s coefficient between the FJS-12 score and a normalised WOMAC and KOOS score
We enrolled 240 consecutive TKR patients performed by a single surgeon into the study. Patients were asked to complete both the FJS and KOOS. The FJS was repeated at 4 weeks for those who responded
The FJS Results were analysed for test-retest reliability using an intraclass correlation coefficient and convergent construct validity was assessessed against the WOMAC and KOOS scores
The WOMAC score was calculated from the KOOS score data
Associate Professor Justin Roe

9. Results 147 patients returned all questionnaires
68 females and 79 males
Mean age 67 years (range 32-89)
Mean time from surgery to completion of first questionnaire 39 months (range 18-72)
Mean time between questionnaires 6 weeks (3-15)
Of the 240 patients a total of 147 patients returned all questionnaires.
Associate Professor Justin Roe

10. Results Mean SD Range FJS-12 Initial 62 29 0-100 Follow-up 60
Normalised WOMAC
Pain 90 13
50-100
Stiffness 84 17
38-100
Function 11
52-100
Total
KOOS
Quality of Life 76 18
12-100
Symptom 65 14
4-100 12
56-100
ADL 89
35-100
Of the 240 patients a total of 147 patients returned all questionairres.
The FJS had mean scores of 62 and 60 whilst the WOMAC had a mean of 90 and the KOOS pain and ADL scores 90 and 89 respectively.
Of note is the much wider standard deviation of the FJS

11. Test Re-test Reliability
Intra Class Correlation
95% Confidence Interval
Landis & Koch Classification
Overall Score
0.97
Almost Perfect
Individual Questions
Night Symptoms
0.88
Sitting
0.84
Walking
0.92
Bathing
Travelling
0.86
Stairs
0.94
Walking uneven ground
0.91
Rising
0.90
Test re-test reliability was Almost perfect across all questions with the overall intra correlation coefficient of 0.97.
Associate Professor Justin Roe

12. Correlation of FJS-12 with Normalised WOMAC
The FJS and the WOMAC demonstrate a positive correlation
The FJS scores have a larger range than the WOMAC scores
This scatter plot shows the positive correlation between the FJS and the normalised WOMAC. Again we see the much broader range of responses of the FJS compared to the WOMAC which is clustered near perfect scores.
Associate Professor Justin Roe

13. Correlation of FJS-12 with Normalised WOMAC and KOOS
Forgotten Joint Score
Spearman’s
Significance
 Normalised WOMAC
 Pain
 0.67
 0.001
Stiffness
0.52
0.001
Function
0.66
Total
0.70
KOOS
Quality of Life
0.63
Symptom
0.33
0.007
Pain
0.68
ADL
The Spearman’s correlation returned a statistically significant positive correlation between all subscores of the WOMAC and KOOS apart from the KOOS symptoms score. Interestingly this was the worst performing score of the KOOS.
Associate Professor Justin Roe

14. Distribution of Scores
FJS
15% > 95
broad distribution
WOMAC
26% > 95
similar distribution, clustered lower
The score distribution of the FJS and the KOOS symptoms scores are demonstrated on these graphs. The FJS has a broad distribution of scores with a smaller cluster of scores near the upper range. The KOOS symptom score has a similar distribution but scores clustered lower.
The FJS had 15% of scores 95 and above
In comparision the WOMAC and KOOS pain score distribution were much more tightly clustered around the perfect score.
The womac had 26% of scores 95 and above. And the KOOS pain 30% perfect scores
30%
perfect scores

15. Ceiling effect WOMAC and KOOS Pain scores demonstrate ceiling effect
Reflects excellent pain relief with TKR
FJS-12 has much wider score distribution
The WOMAC and KOOS pain scores do demonstrate a ceiling effect. This reflects the very good results of TKR especially in relieving pain. The concern is that with so many patients scoring near perfect these scores may have lost their responiveness in these patients that are performing well.
The FJS shows a much wider score distribution and no ceiling effect. It scored similar to the KOOS symptom score and it may be that the lower results in this score reflect patients that do still have ongoing symptoms despite have excellent relief of pain overall.
Associate Professor Justin Roe

16. Discussion FJS-12 similar score distribution to KOOS Symptom score
May reflect ongoing symptoms in well functioning pain free TKR
Associate Professor Justin Roe

17. Summary Forgotten Joint Score has near perfect test-retest reliability
Valid when compared to WOMAC and KOOS
No Ceiling effect
12 question format is quick and easy
Useful adjunct
In summary, the forgotten joint has near perfect test retest reliability and is validated against the WOMAC and KOOS in our study.
It does not demonstrate a ceiling effect in our study.
It’s 12 question format is simple to use and it may prove a useful adjunct in assessing high functioning TKR patients
Associate Professor Justin Roe

18. Thank-you for your attention. See you in Sydney
Associate Professor Justin Roe