Session Information
Session Type: ACR Concurrent Abstract Session
Session Time: 4:30PM-6:00PM
Background/Purpose: Lower limb muscle weakness has been proposed as a factor contributing to functional decline and structural progression. Hip abductor strengthening, in addition to quadriceps strengthening, has been advocated in exercise regimes for persons with knee OA. Individuals with hip weakness are likely to have concomitant quadriceps weakness. It is unknown if strong hip muscles confer additional benefits in the context of strong quadriceps. We examined associations of baseline hip abductor strength with functional decline 5 years later and cartilage damage worsening 2 years later, stratified by baseline quadriceps strength.
Methods: Participants all had knee OA (K/L ≥2) in at least one knee. Isometric hip abductor and knee extensor strength were measured at baseline, using a Biodex Dynamometer. Peak torques were averaged from 3 trials and normalized to body weight. LLFDI (Late-Life Function and Disability Instrument) and chair stand rate were recorded at baseline and 5-year follow-up; scores were analyzed using quintiles. Poor outcomes were defined as remaining in the same low-function quintiles (worst 2 quintiles) or moving into a worse quintile over 5-year follow-up. Participants underwent 3.0T MRI of both knees at baseline and 2 years later. Baseline-to-2-year cartilage damage progression, defined as any worsening of WORMS cartilage damage score, was assessed at each TF and PF articular surface. Knees graded K/L 4 or with severe PF narrowing at baseline were excluded. We assessed associations of baseline hip abductor strength with functional decline and cartilage damage worsening, using logistic regression with generalized estimating equations, adjusting for age, sex, pain, and K/L grade, stratified by strong vs. weak baseline quadriceps strength and by sex.
Results: 187 persons comprised the function outcome sample and 275 knees from 164 persons the structural outcome sample. In persons with stronger knees, greater hip abductor strength was associated with a reduced risk of poor function outcomes, especially in the chair stand rate and LLFDI disability frequency of participation (Table 1). Among stronger knees, greater hip abductor strength was associated with a reduced risk of cartilage damage worsening in the TF compartments (Table 2). For both outcomes, women-only analyses showed similar findings.
Conclusion: In the setting of strong quadriceps, greater hip abductor strength appeared to confer additional beneficial effects on both joint health and long-term function and disability, suggesting an important role for hip abductor strengthening in persons with knee OA.
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Table 1. Person-based subgroup analyses stratified by baseline knee extensor strength and sex: Associations of baseline BW-normalized hip abductor strength (per 0.1 Nm/kg) with baseline-to-5-year poor outcomes by chair stand rate and LLFDI function and disability scores [Odds Ratio (95% CI)]
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Hip Abductor Strength (Nm/kg)
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Chair Stand Rate |
LLFDI Total Function |
LLFDI Basic Lower Extremity Function |
LLFDI Advanced Lower Extremity Function |
LLFDI Disability Frequency of Participation |
LLFDI Disability Limitation |
LLFDI Disability Instrumental Role Limitation |
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In persons with stronger knees (≥ median) (n = 94 persons) |
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Percent with poor outcome |
36.7%
|
50.0% |
45.7% |
56.4% |
47.9%
|
37.2% |
37.2% |
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Adjusteda |
0.75** (0.59, 0.95)
|
0.90 (0.73, 1.11) |
0.86 (0.70, 1.06)
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0.93 (0.75, 1.14)
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0.68** (0.53, 0.87)
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0.83* (0.66, 1.03) |
0.83* (0.66, 1.03) |
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In persons with weaker knees (< median) (n = 93 persons)
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Percent with poor outcome |
44.7%
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68.8%
|
68.8%
|
74.2%
|
49.5% |
53.8%
|
54.8% |
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Adjusteda |
0.92 (0.73, 1.16)
|
0.97 (0.75, 1.24) |
0.97 (0.77, 1.23) |
0.83 (0.64, 1.08) |
1.02 (0.82, 1.27)
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0.98 (0.79, 1.23) |
1.16 (0.91, 1.47) |
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In women with stronger knees (≥ median in women) (n = 74 women§)
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Percent with poor outcome
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34.7%
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41.9% |
40.5% |
48.6% |
39.2% |
37.8% |
37.8% |
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Adjustedb |
0.83 (0.65, 1.06) |
0.89 (0.71, 1.12) |
0.94 (0.75, 1.18) |
0.93 (0.75, 1.16) |
0.71** (0.55, 0.93)
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0.80* (0.62, 1.04) |
0.80* (0.62, 1.04) |
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In women with weaker knees (< median in women) (n = 73 women§) |
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Percent with poor outcome |
43.1% |
68.5% |
68.5% |
74.0% |
49.3% |
50.7% |
52.1% |
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Adjustedb |
0.84 (0.64, 1.10) |
0.95 (0.72, 1.26) |
0.90 (0.70, 1.17) |
0.80 (0.60, 1.06) |
1.07 (0.84, 1.36)
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0.93 (0.72, 1.18) |
1.06 (0.83, 1.35) |
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Abbreviations: LLFDI, Late Life Function Disability Instrument; CI, confidence interval; BW, body weight, BMI, body mass index; K/L, Kellgren/Lawrence aAdjusted for age, sex, hip pain during strength testing, and K/L grade of the knee with worse baseline hip abductor strength bAdjusted for age, hip pain during strength testing, and K/L grade of the knee with worse baseline hip abductor strength §A total of 147 women **odds ratio (OR) with associated 95% CI that excludes 1.0 is considered statistically significant *p<0.10 |
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Table 2. Knee-based subgroup analyses stratified by baseline knee extensor strength and sex: Associations of baseline BW-normalized hip abductor strength (per 0.1 Nm/kg) with baseline-to-2-year tibiofemoral and patellofemoral cartilage damage worsening outcomes [Odds Ratio (95% CI)]
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Baseline Hip Abductor Strength (Nm/kg)
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Any TF |
Medial TF |
Lateral TF |
Any PF |
Medial PF |
Lateral PF |
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In stronger knees (≥ median) (n = 138 knees from 99 persons) |
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Percent with poor outcome |
22.5% |
11.6% |
12.3% |
17.4% |
8.0% |
10.1% |
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Adjusteda |
0.73** (0.57, 0.93) |
0.77* (0.57, 1.05) |
0.72* (0.52, 1.02) |
0.89 (0.66, 1.21) |
0.86 (0.60, 1.23)
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0.93 (0.67, 1.29) |
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In weaker knees (< median) (n = 137 knees from 96 persons) |
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Percent with poor outcome |
24.8% |
16.1% |
9.5% |
16.1%
|
11.7% |
6.6%
|
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Adjusteda |
1.06 (0.86, 1.32)
|
1.19 (0.90, 1.58) |
N/A# |
N/A# |
N/A# |
N/A#
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In stronger knees (≥ median in women) among women (n = 112 knees§ from 74 women) |
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Percent with poor outcome |
21.4% |
12.5% |
9.8% |
21.4% |
12.5% |
10.7% |
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Adjustedb |
0.83* (0.67, 1.03)
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0.76** (0.58, 0.99) |
0.97 (0.67, 1.39) |
0.72 (0.46, 1.14) |
0.66* (0.42, 1.02) |
0.80 (0.48, 1.33) |
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In weaker knees (< median in women) among women (n = 111 knees§ from 75 women) |
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Percent with poor outcome |
25.2% |
14.4% |
11.7% |
15.3% |
9.9% |
7.2%
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Adjustedb |
1.03 (0.82, 1.31) |
1.14 (0.82, 1.60)
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0.87 (0.64, 1.18) |
0.80** (0.65, 0.98) |
0.80 (0.61, 1.05) |
0.73** (0.56, 0.94) |
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Abbreviations: BW, body weight; CI, confidence interval; TF, tibiofemoral; PF, patellofemoral; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; K/L, Kellgren/Lawrence aAdjusted for age, sex, WOMAC pain, and K/L grade bAdjusted for age, WOMAC pain, and K/L grade #No men had structural progression in this compartment §A total of 223 knees from women **odds ratio (OR) with associated 95% CI that excludes 1.0 is considered statistically significant *p<0.10
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To cite this abstract in AMA style:
Chang AH, Chmiel JS, Almagor O, Hayes KW, Guermazi A, Pottumarthi P, Moisio KC, Zhang Y, Szymaszek J, Sharma L. Lower Limb Muscle Strength and Protection Against Functional Decline and Structural Worsening in Knee Osteoarthritis [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 9). https://acrabstracts.org/abstract/lower-limb-muscle-strength-and-protection-against-functional-decline-and-structural-worsening-in-knee-osteoarthritis/. Accessed .« Back to 2018 ACR/ARHP Annual Meeting
ACR Meeting Abstracts - https://acrabstracts.org/abstract/lower-limb-muscle-strength-and-protection-against-functional-decline-and-structural-worsening-in-knee-osteoarthritis/