Background/Purpose: Little research has explored participation outcomes, defined as involvement in life situations, among persons following knee replacement (KR). We recently reported (OARSI 2012) that persons undergoing KR did not necessarily show improvement in participation after surgery. These findings, however, could be due to confounding by indication, thus we sought to examine whether participation restriction differed among persons following KR compared to similarly matched group with symptomatic knee osteoarthritis (OA).
Methods: Subjects were selected from the Multicenter Osteoarthritis (MOST) Study and the Osteoarthritis Initiative (OAI). We took the pre-KR pain and physical function WOMAC scores of MOST and OAI subjects who were at least one year after KR and matched each of these by quartiles to 1-2 subjects with symptomatic knee OA, (defined as radiographic evidence of knee OA and frequent knee pain over the last 30 days). Participation was measured using the Late Life Disability Instrument (LLDI) at the 60 month visit in MOST and at 48 months in OAI; restriction was defined using a previously established cut-point of < 69/100 on the Instrumental Limitation subscale of the LLDI (LLDI-IL). Data on covariates was collected at the pre-KR/index visit.
We compared the proportion of subjects with participation restrictions for each group overall and stratified by sex, race, age (< 65, 65-74, ≥75 years), # of comorbidities (> 1), and depressive symptoms (> 16 on CES-D) using chi square analyses. We evaluated the association between KR status and participation restrictions while adjusting for the above covariates, as well as body mass index, educational level, and presence of lower limb or back pain, using conditional logistic regression.
Results: Participation restriction was assessed on average 3 years post-KR and was common in both the post-KR group (45%) and in those with SxOA who had comparable pain/function (43%). There were no statistical differences in the proportion of participation restriction among subjects in each KR group overall or after stratification. The SxOA group had more younger subjects, fewer Whites and more with other lower limb pain (Table 1). After adjusting for these differences in groups, there was no difference in the odds of participation restriction among subjects with KR compared to those with SxOA (OR 1.0 (0.6, 1.6). Other factors independently associated with participation restrictions included male sex and increased depressive symptoms (Table 2).
Conclusion: Despite prior evidence of improvements in pain and function after knee replacement, the current study demonstrates that after KR, there is no clear difference between those who underwent KR and those who still have SxOA in terms of participation in life activities. Other factors such as sex and depressive symptoms may play more of a role in one’s involvement in life situations.
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Table 1. Demographic and clinical status of study subjects at pre-KR visit
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Independent Variable |
Knee Replacement Group
|
Symptomatic Osteoarthritis Group
|
p-value
|
|
Total, n |
277 |
552 |
|
|
Sex: Women, % |
66 |
64 |
.5 |
|
Race: White , % |
86 |
76 |
.0007 |
|
Age: <65 years, % |
46 |
55 |
.01 |
|
65-74 years, % |
45 |
35 |
.006 |
|
75+ years, % |
9 |
10 |
0.8 |
|
Body Mass Index, mean (SD) |
32.2 (6.4) |
32.4 (6.6) |
.99 |
|
Comorbidities: > 1, %
|
43 |
43 |
0.9 |
|
Depressive Symptoms: > 16, % |
15 |
17 |
0.3 |
|
Education: < High School, % |
5 |
6 |
0.6 |
|
Pain in lower limbs/back, % |
75 |
83 |
.01 |
|
WOMAC physical function, mean (SD), range 0-68 |
26.2 (11.7)* |
26.1 (11.8)* |
0.8 |
|
WOMAC pain, mean (SD), range 0-20 |
8.1 (3.8)* |
8.1 (3.8)* |
0.9 |
|
*Knee replacement and symptomatic OA group matched on these variables
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Table 2: Effect of Demographic and Clinical Factors on Participation Restrictions
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Independent Variable |
Unadjusted OR (95%CI) |
Adjusted OR (95% CI)** |
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|
Knee Replacement Status (ref=SxOA)
|
0.9 (0.6, 1.4)
|
1.0 (0.6, 1.6) |
|
|
Sex (ref=male) |
0.7 (0.4, 1.1)
|
0.6 (0.4, 1.0)
|
|
|
Race (ref= White) |
1.3 (1.2, 1.3) |
0.9 (0.5, 1.8)
|
|
|
Age at KR: (ref= <65) |
ref |
ref
|
|
|
65-74
|
1.5 (1.0, 2.3) |
1.4 (0.9, 2.3)
|
|
|
75+
|
0.4 (0.2, 1.0) |
0.8 (0.3, 1.9)
|
|
|
Educational status (ref < High school) |
1.2 (0.5, 2.9) |
1.1 (0.4, 2.6)
|
|
|
Number of Comorbidities (ref ≤ 1) |
1.7 (1.1, 2.7) |
1.5 (0.9, 2.5)
|
|
|
Body Mass Index (ref <30) |
1.8 (1.1, 2.7) |
1.6 (0.9, 2.6) |
|
|
Depressive Symptoms (ref≤16) |
2.9 (1.5, 5.3)
|
2.3 (1.2, 4.5)
|
|
|
Lower Limb and Back Pain |
1.4 (0.8, 2.5) |
1.3 (0.7, 2.5)
|
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**Adjusted for KR group, sex, race, age category, educational status, # of comorbidities, bmi, depressive symtpoms, lower limb and back pain |
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.
Disclosure:
J. L. Maxwell,
None;
J. Niu,
None;
J. J. Keysor,
None;
T. Neogi,
None;
T. Yang,
None;
M. C. Nevitt,
None;
J. A. Singh,
research and travel grants from Takeda, Savient, Wyeth and Amgen,
2,
J.A.S. has received speaker honoraria from Abbott,
,
; aConsultant fees from URL pharmaceuticals, Savient, Takeda, Ardea, Allergan and Novartis.,
5;
L. Frey-Law,
None;
D. T. Felson,
None.
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