Total Knee Functional Outcome Measure Doesn’t Measure Function

Comparison of self-reported knee injury and osteoarthritis outcome score to performance measures in patients after total knee arthroplasty. PM&R. 2011 Jun;3(6):541-9 Stevens-Lapsley JE1, Schenkman ML, Dayton MR.

Abstract
OBJECTIVE:
To characterize patient outcomes after total knee arthroplasty (TKA) by (1) examining changes in self-report measures (Knee Injury and Osteoarthritis Outcome Score [KOOS]) and performance measures over the first 6 months after TKA, (2) evaluating correlations between changes in KOOS self-report function (activities of daily living [ADL] subscale) and functional performance (6-minute walk [6MW]), and (3) exploring how changes in pain correlate with KOOS ADL and 6MW outcomes.
DESIGN:
Retrospective cohort evaluation.
SETTING:
Clinical research laboratory. PATIENTS (OR PARTICIPANTS): Thirty-nine patients scheduled for a unilateral, primary TKA for end-stage unilateral knee osteoarthritis.
METHODS:
Patients were evaluated 2 weeks before surgery and 1, 3, and 6 months after surgery.
MAIN OUTCOME MEASUREMENTS:
KOOS, 6MW, timed-up-and-go (TUG), and stair climbing tests (SCT), quadriceps strength.
RESULTS:
Three of 5 KOOS subscales significantly improved by 1 month after TKA. All 5 KOOS subscales significantly improved by 3 and 6 months after TKA. In contrast, performance measures (6MW, TUG, SCT, and quadriceps strength) all significantly declined from preoperative values by 1 month after TKA and significantly improved from preoperative values by 3 and 6 months after TKA; yet, improvements from preoperative values were not clinically meaningful. Pearson correlations between changes in the KOOS ADL subscale and 6MW from before surgery were not statistically significant at 1, 3, or 6 months after TKA. In addition, KOOS Pain was strongly correlated with KOOS ADL scores at all times, but KOOS Pain was not correlated with 6MW distance at any time.
CONCLUSIONS:
Patient self-report by using the KOOS did not reflect the magnitude of performance deficits present after surgery, especially 1 month after TKA. Self-report KOOS outcomes closely paralleled pain relief after surgery, whereas performance measures were not correlated with pain. These results emphasize the importance of including performance measures when tracking recovery after TKA as opposed to solely relying on self-reported measures.

My comments:

My experience agrees with this study as do a number of other studies which find that patients are generally very satisfied after total knee replacement largely because they feel better. However, performance measures (how well they can walk, balance, strength and endurance) are often still well below where they should be in comparison to age-matched healthy control subjects.

This paper found that self reported surveys of performance, often required by insurance companies for authorizing physical therapy treatments, do not capture the true level of functional impairments. This leads to early discharge from treatment before normal function is restored, resulting in long term impairment. As this paper states, objective performance measures like gait speed, timed up and go, stair, squat, strength and balance tests should be the criterion in which function is measured. Pain is certainly important, but pain is best captured on a pain scale, and as this study found the KOOS functional test correlated more with pain than with function.

I’ve noticed a number of insurance companies are using this discrepancy to deny treatment when the patient is still making objective improvements. The patient still has performance impairments but they are not captured in their “outcome measure” questionnaire, so the insurance company denies further treatment. It reminds me much of that movie Sicko. While this particular paper is regarding function after total knee replacement, I would be surprised if it isn’t much the same regarding to every other body part.  I’ll have to look that up.

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Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed his Yoga Teacher Training at Sampoorna Yoga in Goa, India.