Change in KOOS and WOMAC Scores from Pre-injury Baseline in a Young Athletic Population with And without ACL Injury over FourYears of Follow-up

Abstract

Objectives:

Several studies have examined changes in patient reported outcome measures (PROMS) following ACL injury but no studies to date have prospectively evaluated changes from pre-injury baseline through injury and follow-up in ACL injured cases and uninjured controls. The purpose of this study was to examine changes in PROMS over time from pre-injury baseline to at least 2 years following ACL reconstruction and to compare this to changes in an uninjured control group with similar physical activity requirements.

Methods:

We conducted a prospective cohort study with a nested case-control analysis at a US service academy. All incoming freshmen were recruited to participate in this study. Within the first week of arrival all subjects completed a baseline questionnaire that contained information about demographics, injury history, and standardized PROMS including the KOOS, WOMAC, and Marx Activity Rating Scale (MARS). Subjects who subsequently sustained an ACL injury during their four years at the academy completed post injury assessments at the time of surgery and at 6-months, 12-months, and 24-months post-surgery. Controls with no history of knee joint injury at baseline, and no knee joint injury during the follow-up period, were recruited to repeat the baseline assessments within 1 year of graduation. Within group changes from pre-injury baseline to the final follow-up, and between group differences at these time points (baseline and final follow-up) were evaluated with dependent and independent t-tests, respectively. We also compared these results with established minimum clinically important difference (MCID) values.

Results:

Of the 1268 freshman entering the academy, 1177 consented to participate in this study. Males made up 82% of the cohort with an average age at enrollment of 19±1 years. Of those enrolled, 30 ACL injured cases with no history of injury at baseline met the inclusion criteria for this study. Ninety-two uninjured controls who also met the inclusion criteria completed follow-up assessments. There were no statistically significant pre-injury baseline differences between the ACL injured cases and uninjured controls on any of the PROMS except for the KOOS sports and recreation subscale, but this difference did not exceeded the MCID (Table 1). There were statistically significant differences across all KOOS and WOMAC subscales between ACL injured cases and uninjured controls at the time of the final follow-up assessment (Table 1). Four of the KOOS subscales (Pain, Symptoms, Sport, QOL) and the WOMAC stiffness subscale demonstrated greater than 8 point differences between groups, which exceeded the established MCID for these instruments (Figure 1A and 1B). There were no significant differences between ACL injured cases and uninjured controls on the MARS (p=0.635) at the time of the final follow-up. The ACL injured cases also reported significant deficits on the WOMAC stiffness (p=0.032) subscale, the MARS (p=0.030), and all KOOS subscales, with the exception of Function, at the time of final follow-up compared to their pre-injury baseline scores. These deficits exceeded the established MCID values for three of the KOOS subscales and the MARS.

Conclusion:

ACL injured cases reported significant deficits on PROMS at least 2 years following surgical reconstruction in relation to pre-injury baseline scores and uninjured controls. Many of these deficits exceeded established MCID values.

Table 1:

Between Group Differences at Pre-injury Baseline and Follow-up for ACL Injured Cases and Uninjured Controls.

		Pre-injury Baseline					Follow-up
		ACL injured Cases		Uninjured Controls			ACL injured Cases		Uninjured Controls
		Mean	SD	Mean	SD	p	Mean	SD	Mean	SD	p
KOOS
	Pain	96.44	6.80	97.25	5.07	0.413	90.30	9.34	98.86	4.45	<0.001*
	Symptoms	92.84	7.61	94.34	7.24	0.252	80.93	14.83	95.63	7.63	<0.001*
	Function	98.00	3.96	98.64	2.72	0.273	97.10	3.84	99.52	2.79	<0.001*
	Sports Function	88.00	19.81	95.00	9.38	0.029	77.83	17.75	97.45	7.72	<0.001*
	QOL	87.74	12.79	91.91	11.34	0.064	66.17	22.29	94.34	14.47	<0.001*
WOMAC
	Pain	97.11	6.08	97.91	4.54	0.384	95.50	6.87	99.18	3.58	<0.001
	Stiffness	90.35	11.68	90.85	14.41	0.856	83.10	17.16	93.84	10.47	<0.001*
	Function	98.00	3.96	98.66	2.68	0.255	97.10	3.84	99.52	2.79	<0.001
MARS
	Activity	12.53	3.76	11.95	3.54	0.406	10.30	4.78	10.71	3.93	0.64

*Between Group Difference Exceeds the Established Minimum Clinically Important Difference (MCID).