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RehabMeasures Instrument

Knee Injury and Osteoarthritis Outcome Score

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Atomized Content

Purpose

A 42-item self-administered assessment of five outcomes: knee-related quality of life, activities of daily living, sport and recreation function, symptoms, and pain.

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Instrument Details

Acronym KOOS

Area of Assessment

Activities of Daily Living
Pain
Quality of Life

Assessment Type

Patient Reported Outcomes

Administration Mode

Paper & Pencil

Cost

Free

Diagnosis/Conditions

  • Arthritis + Joint Conditions
  • Sports & Musculoskeletal Injuries

Key Descriptions

  • Based on the Western Ontario and Mc-Master Universities Osteoarthritis Index (WOMAC).
  • Each item is scored from 0 (no problems) to 4 (extreme problems).
  • For each subscale, the score is then normalized to a 0-100 scale with higher scores equaling better status.

Number of Items

42

Time to Administer

10 minutes

Required Training

No Training

Age Ranges

Adolescent

13 - 17

years

Adult

18 - 64

years

Elderly Adult

65 +

years

Instrument Reviewers

Initially reviewed by Jason Raad, MS in 4/2012

Body Part

Lower Extremity

ICF Domain

Body Function
Activity

Measurement Domain

General Health

Considerations

  • The KOOS is available in several languages, the American-English, Swedish, and Danish versions have been validated (www.koos.nu); a French version (Ornetti et al., 2008); a Japanese version (Nakamura, 2011); and a Singapore English and Chinese version (Xie et al., 2006) have each had at least one validation study conducted. Visit the Koos website for a complete list of translated instruments.

  • Modified versions include:

    • FAOS: Assesses problems with the foot and ankle

    • HOOS: Assesses problems with the hip

    • RAOS: Assesses hip, knee and foot problems in patients with rheumatoid arthritis 

  • A Physical Function (KOOS-PS) is also available

  • A Children’s Version (KOOS-Child) is also available

Do you see an error or have a suggestion for this instrument summary? Please e-mail us!

Non-Specific Patient Population

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Standard Error of Measurement (SEM)

Athletes:

(Salavati et al, 2011; n = 57 patients with ACL reconstruction (39 males, 18 females); mean age = 25.6 ± 3.4 years, Athletes) 

Domain

SEM

Pain 

2.2 

Symptoms 

3.1 

ADL 

2.9 

Sports/Rec 

2.1 

QoL 

2.6

Minimal Detectable Change (MDC)

Athletes:

(Salavati et al, 2011, Athletes) 

Domain

MDC

Pain 

6.1 

Symptoms 

8.5 

ADL 

8.0 

Sport/Rec 

5.8 

QoL 

7.2 

Cut-Off Scores

Athletes/ACL Injury:

(Lohmander LS et al, 2004; n = 84; mean age = 31 (26-40) years; mean BMI = 23 (18-40) kg/m2, Athletes/ACL Injury) 

 

 

Cut-Off Score for Problematic Knee

Pain 

< 86.1

Symptoms 

< 85.7

ADL 

< 86.8

Sport/Rec 

< 85.0

QoL 

< 87.5

 

Total Knee Arthroplasty:

(Stevens-Lapsley et al; 2011; n = 39 (17 men and 22 women) mean age = 64.0 (8.2) years; mean (SD) BMI, 29.1 (5.2) kg/m2, Total Knee Arthroplasty)

 

Comparison between pre-op and post-op KOOS scores:

 

 

 

 

 

 

 

 

Pre-op

 

1-Mo Postop

 

 

3-Mo Postop

 

 

6-Mo Postop

 

Measure

Mean(SD)

Mean(SD)

p

Mean(SD)

p

Mean(SD)

p

KOOS ADL

58.33 (2.41)

69.29 (2.21)

p < 0.05

84.35 (2.74)

p < 0.05

87.92 (2.12)

p < 0.05

KOOS symptom

48.08 (2.64)

53.39 (1.99)

 

66.21 (2.72)

p < 0.05

72.37 (2.69)

p < 0.05

KOOS Sport/Rec

18.72 (3.42)

18.17 (3.46)

 

49.23 (3.42)

p < 0.05

50.53 (3.46)

p < 0.05

KOOS QOL

26.12 (2.98)

41.31 (3.01)

p < 0.05

63.30 (2.98)

p < 0.05

66.96 (3.01)

p < 0.05

KOOS Pain

48.22 (2.63)

59.19 (2.63)

p < 0.05

75.28 (2.63)

p < 0.05

80.94 (2.65)

p < 0.05

6MW (m)

430 (18)

349 (18)

p < 0.05

459 (18)

p < 0.05

473 (18)

p < 0.05

TUG (s)

9.23 (0.55)

12.15 (0.99)

p < 0.05

8.46 (0.50)

p < 0.05

7.92 (0.41)

p < 0.05

SCT (s) 

17.87 (1.72)

31.83 (3.33)

p < 0.05

16.05 (1.49)

p < 0.05

14.25 (1.29)

p < 0.05

Normative Data

Athletes:

(Salavati et al, 2011, Athletes)

 

KOOS Post-operation Baseline Norms:

 

Domain

Value: Mean (SD )

Pain

74.0 (10.2)

Symptoms

61.2 (9.3)

ADL

73.0 (8.9)

Sports / Recreation Level

51.1 (15.3)

QoL

52.9 (13.9)

 

ACL/Athletes:

(Kvist J et al, 2005; n= 62; mean age= 27 (18-37) years, ACL/Athletes) 

 

 

Men

Women

Total

Pain 

85 + 19 (n = 33) 

82 + 17 (n = 27) 

84 + 18 (n = 60) 

Symptoms 

75 + 16 (n = 34) 

74 + 25 (n = 28) 

74 + 20 (n = 62) 

ADL 

94 + 8 (n = 34) 

90 + 14 (n = 28) 

92 + 12 (n = 62) 

Sport/Rec 

64 + 23 (n = 34) 

60 + 28 (n = 28) 

62 + 25 (n = 62) 

QoL 

64 + 20 (n = 33) 

63 + 22 (n = 28) 

64 + 21 (n = 61) 

 

ACL Lesion:

(Hill GN, O’Leary ST, 2012; n=165; mean age 30.4(+ 9.7), years; 74% male; mean time to surgery following lesion 13.1(+ 20.8) months, ACL Lesion) 

  • Significant improvements in all subscales at 12 months following ACL reconstruction (p < 0.001) 
  • Improvement seen at 3 and 6 month measurements (p < 0.003) 
  • Reduced rate of recovery in Sports/rec and QoL subscales 
  • Sports/rec and QoL most sensitive to change 

 

(Ahlden M et al, 2012; = 17,794; 57.5% male; primary reconstruction n= 15,387, revision = 964; cause of injury-soccer in 1/2 of males, soccer 1/3 of females, ACL Lesion) 

  • Primary ACL Reconstruction 
    • All subscales significantly improved at 1, 2, and 5 years post-op (p < 0.001)
  • Revision 
    • Significantly improved at 1 and 2 years post-op (p < 0.05) 
    • At 5 years, only Sport/rec and QoL were improved (p < 0.002) 
  • Significantly poorer knee-related QOL in revision patients than primary reconstructions 
  • ACL reconstruction with additional intra-articular injuries 
    • Scored significantly lower on all subscales pre-op compared to ACL only (p < 0.001)

 

(von Porat A, Roos EM, Roos H, 2004; = 219; mean age 38 (range 30-56) years, Athletes/ACL Lesion) 

  • Significant differences were found in all KOOS subscales comparing ACL lesion with published reference groups

Study Group

 

 

Reference Group

 

 

Mean (SD)

95% CI

Mean (SD)

95% CI

Pain

84 (16.1)

81.9-87.1

96 (9.9)

93.7-99.0

Symptoms

76 (20.2)

72.5-79.0

94 (9.9)

92.3-96.9

ADL

90 (13.5)

88.3-92.6

96 (10.0)

93.2-98.5

Sport/Rec

63 (28.7)

58.9-68.0

90 (17.9)

85.6-95.1

QoL

60 (24.6)

56.2-63.9

92 (13.5)

88.6-95.7

 

Partial medial meniscectomy 3–5 years previously:

(Roos et al, 2005; n = 14, 10 men and 4 women; 7 participants reported at least mild functional difficulty; mean age = 45.8 (3.6) years; BML = 26.8 (2.6), Partial medial meniscectomy)

KOOS Baseline Norms:

 

Domain

Value: Mean (SD)

Pain

80 (17)

Symptoms

81 (12)

ADL

83 (17)

Sports / Recreation Level

60 (26)

QOL

68 (18)

Test/Retest Reliability

Athletes: (Salavati et al, 2011)

  • All KOOS subscales ICC higher than acceptable level of 0.70 (range=0.75-0.93) 
  • Cronbach’s alpha was higher than 0.70 in all KOOS subscales

 

Articular Cartilage Lesion: (Engelhart et al, 2012; = 54; age range 25-52 years, 67% male; 80% post-surgical repair of cartilage lesions; median BMI=27; n=33 (based on PR Functional Status Score)

KOOS: Reliability and Test-retest Reliability:

 

Domain

ICC (95% CI)

Pain

0.82

Symptoms

0.78

ADL

0.79

Sports / Recreation Level

0.80

QoL

0.82

 

Symptomatic Focal Cartilage Lesion: (Bekkers et al, 2009; = 40; mean age 35 (12) years, 70% female; cartilage lesions were the result of autologous chondrocyte implantation (n = 20) or microfracturing (n = 20); mean postoperative time was 32 months; Dutch version)

KOOS: Reliability and Test-retest Reliability

 

 

 

 

Domain

Mean KOOS (SD)

 

ICC (95% CI)

SDD

 

First

Second*

 

 

Symptoms

74 (17)

75 (17)

0.95 (0.90 - 0.97)

5

Pain

77 (15)

77 (15)

0.92 (0.86 - 0.96)

6

Function ADL

84 (14)

86 (12)

0.87 (0.77 - 0.93)

7

Sport/recreation

55 (26)

58 (25)

0.89 (0.81 - 0.93)

12

QOL

49 (23)

53 (22)

0.95 (0.91 - 0.97)

7

Total score

74 (15)

76 (14)

0.97 (0.93 - 0.98)

4

*two-day retest interval

 

 

 

 

Internal Consistency

Athletes: 

(Salavati et al, 2011, Athletes)

  • All KOOS subscales ICC higher than acceptable level of 0.70 (range = 0.75-0.93) 
  • Cronbach’s alpha was higher than 0.70 in all KOOS subscales

 

Articular Cartilage Lesion:

(Engelhart et al, 2012; = 54; age range 25-52 years, 67% male; 80% post-surgical repair of cartilage lesions; median BMI=27; n=33 (based on PR Functional Status Score, Articular Cartilage Lesion)

KOOS: Reliability and Test-retest Reliability:

 

Domain

ICC (95% CI)

Pain

0.82

Symptoms

0.78

ADL

0.79

Sports / Recreation Level

0.80

QoL

0.82

 

Symptomatic Focal Cartilage Lesion:

(Bekkers et al, 2009; = 40; mean age 35 (12) years, 70% female; cartilage lesions were the result of autologous chondrocyte implantation (n = 20) or microfracturing (n = 20); mean postoperative time was 32 months; Dutch version, Symptomatic Focal Cartilage Lesion)

KOOS: Reliability and Test-retest Reliability

 

 

 

 

Domain

Mean KOOS (SD)

 

ICC (95% CI)

SDD

 

First

Second*

 

 

Symptoms

74 (17)

75 (17)

0.95 (0.90 - 0.97)

5

Pain

77 (15)

77 (15)

0.92 (0.86 - 0.96)

6

Function ADL

84 (14)

86 (12)

0.87 (0.77 - 0.93)

7

Sport/recreation

55 (26)

58 (25)

0.89 (0.81 - 0.93)

12

QOL

49 (23)

53 (22)

0.95 (0.91 - 0.97)

7

Total score

74 (15)

76 (14)

0.97 (0.93 - 0.98)

4

*two-day retest interval

 

 

 

 

Criterion Validity (Predictive/Concurrent)

Athletes/ACL Injury:

(Lohmander LS et al, 2004, Athletes/ACL Injury) 

  • Worse KOOS score predicted for all five dimensions in ACL-injured female soccer players (p < 0.001) compared to uninjured soccer players 
    • Largest differences found in Sports/Rec and QoL (p < 0.001)

 

Construct Validity

Articular cartilage lesion:

(Engelhart et al, 2012, Articular Cartilage Lesion) 

  • Strong correlation between the following: 
    • KOOS subscales and physical outcomes of SF-36 (PF, RL, and BP) (r > 0.50) 

 

Athletes:

(Salavati et al, 2011, Athletes) 

  • Strong correlation between the following: 
    • KOOS pain and SF-36 BP (= 0.79, p < 0.01) 
    • KOOS ADL and SF-36 PF (= 0.73, p < 0.01) 
    • KOOS Sport/rec and SF-36 PF (= 0.72, p< 0.01)

Total Knee Arthroplasty:

(Stevens-Lapsley et al, 2011, Total Knee Arthroplasty) 

KOOS and 6MW Correlations:

 

 

Months

KOOS ADL versus 6MW

KOOS Pain versus 6MW

1

-0.096 (p = 0.577)

-0.272 (p = 0.108)

3

0.021 (p = 0.899)

-0.038 (p = 0.818)

6

-0.178 (p = 0.291)

-0.230 (p = 0.171)

 

 

 

6MW = 6-minute walk

 

 

Content Validity

  • Content Validity for participants with ACL and meniscus injury, and early OA a literature review was conducted, a panel of experts was consulted and a pilot study was conducted (Roos and Toksvig-Larsen, 2003)
  • In determining whether or not to have TJR, greater than 90% of patients rated all KOOS subscales (except Sport/Rec) as “extremely or very important” (Roos et al, 2003)

Floor/Ceiling Effects

Symptomatic Focal Cartilage Lesion:

(Bekkers et al, 2009, Symbtomatic Focal Cartilage Lesion)

KOOS Floor and Ceiling

 

 

Domain

Floor

Ceiling

Symptoms

0%

2.6%

Pain

0%

5.1%

Function ADL

0%

7.7%

Sport/recreation

0%

7.7%

QOL

0%

10.3%

Total score

0%

2.6%

Responsiveness

Articular Cartilage Lesion:

(Engelhart et al, 2012, Articular Cartilage Lesion)

  • Large Guyatt statistics for Sport/rec (1.06) and QoL (0.91)
  • Moderate Guyatt statistics for symptoms (0.55), pain (0.51), and ADL (0.51) 

 

 

Symptomatic Focal Cartilage Lesion:

(Bekkers et al, 2009, Symptomatic Focal Cartilage Lesion)

 

Responsiveness:

 

Domain

ES

Symptoms

0.72

Pain

0.82

Function ADL

0.70

Sport/recreation

0.98

QOL

1.32

Total score

0.91

Joint Pain and Fractures

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Minimal Detectable Change (MDC)

Osteoarthritis and Total Joint Replacement:

(Roos and Toksvig-Larsen, 2003; n = 105 patients with total knee replacements (39 males, 66 female); mean age = 71.3 (43-86) years, Osteoarthritis and Total Joint Replacement)

  • A change of 8-10 points may represent a minimal perceptible clinical improvement (MPCI)

Cut-Off Scores

Total Joint Replacement:

(Roos et al; 2003, Total Joint Replacement) 

 

 

Baseline 

6 months 

12 months 

Pain 

38 (18)

79 (20) 

83 (16) 

Symptoms 

47 (20) 

72 (18) 

84 (16) 

ADL 

41 (16) 

77 (17) 

82 (16) 

Sport/Rec 

16 (22) 

48 (33) 

46 (30) 

QoL 

19 (14) 

59 (25) 

69 (24)

Criterion Validity (Predictive/Concurrent)

Total Joint Replacement:

(Tonelli SM, 2011; = 138 women, 70 men; mean age = Women 61.92 (10.03) years, Men 61.66 (9.92) years; mean BMI = Women 35.43, Men 33.19, Total Joint Replacement) 

  • Women have worse scores than men in pain and ADL subscores prior to TKR (ppain= 0.02; pADL= 0.007)

Construct Validity

Total Joint Replacement:

(Argenson JN; = 445; mean age 71 ± 8 years; mean BMI=28 ± 4 kg/m2 ,Total Knee Replacement)

KOOS and Knee Flexion:

 

 

SUBSCALE

Pearson Coefficient

P value vs. Flexion

Pain

0.437

< 0.0001

Symptoms

0.434

< 0.0001

ADL

0.437

< 0.0001

Sport/Rec

0.212

0.0014

QoL

0.379

< 0.0001

(Roos et al, 2003, Total Knee Replacement) 

  • High correlations between SF-36 scales and KOOS scales that are designed to measure similar constructs 
    • Bodily Pain (SF-36) vs. Pain (KOOS)- rs= 0.62 
    • Physical Function (SF-36) vs. ADL (KOOS)- rs = 0.

Floor/Ceiling Effects

Total Joint Replacement:

(Roos et. al 2003, Total Joint Replacement) 

  • KOOS is better predictor of post-op improvement in comparison to WOMAC, as exhibited by lower ceiling effects in KOOS

 

KOOS Ceiling/Floor Scores

 

 

 

Pre-Op

6 months

12 months

Pain

1/0

15/0

22/0

Symptoms

0/1

3/0

12/0

ADL

0/0

8/0

11/0

Sport/Rec

0/48

16/16

9/12

QoL

0/14

11/1

17/0

Responsiveness

Total Joint Replacement:

(Roos et al, 2003, Total Joint Replacement)

  • QoL has largest effect size (2.86 @ 6 months post-op & 3.54 @ 12 months)

Osteoarthritis

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Minimal Detectable Change (MDC)

Osteoarthritis and Total Joint Replacement:

(Roos and Toksvig-Larsen, 2003; n = 105 patients with total knee replacements (39 males, 66 female); mean age = 71.3 (43-86) years, Osteoarthritis and Total Joint Replacement)

  • A change of 8-10 points may represent a minimal perceptible clinical improvement (MPCI)

Normative Data

Knee Osteoarthritis:

(Xie et al, 2006; n = 127 English and n = 131 Chinese speakers; mean age for English speakers = 65.3 (7.9), and Chinese speakers = 67.8 (7.1) years; BMI (English) 28.6 (5.4) and Chinese 27.8 (3.9);  mean duration of OA (English) 5.9 (5.6) and (Chinese) 6.1 (4.7) years; study conducted in Singapore)

Comparing knee OA between language groups:

 

 

 

Singapore English Version (n = 127)

 

 

 

KOOS Domain

Mean (SD)

Median

% Floor / Ceiling

Pain

57.0 (16.0)

58.3

0/0

Symptoms

59.8 (19.1)

60.7

0/0

ADL

60.8 (16.9)

64.7

0/0

Sport & Rec

6.6 (12.2)

0.0

66.9/0

QOL

39.6 (18.8)

43.8

3.1/0

 

 

 

 

 

Singapore Chinese Version (n = 131)

 

 

 

Pain

57.3 (12.9)

58.3

0/0

Symptoms

63.2 (17.8)

64.3

0/1.5

ADL

62.2 (13.0)

61.8

0/0

Sport & Rec

4.8 (9.4)

0.0

73.3/0

QOL

42.9 (19.4)

43.8

0/1.5

Test/Retest Reliability

Knee Osteoarthritis: (Xie et al, 2006)

 

Comparing knee OA between language groups:

 

 

Singapore English Version (n = 127)

 

 

KOOS Domain

Mean (SD)

Test-retest ICC

Pain

57.0 (16.0)

0.88

Symptoms

59.8 (19.1)

0.87

ADL

60.8 (16.9)

0.91

Sport & Rec

6.6 (12.2)

0.65

QOL

39.6 (18.8)

0.86

 

 

 

 

 

Singapore Chinese Version (n = 131)

 

 

Pain

57.3 (12.9)

0.87

Symptoms

63.2 (17.8)

0.85

ADL

62.2 (13.0)

0.84

Sport & Rec

4.8 (9.4)

0.78

QOL

42.9 (19.4)

0.60

Internal Consistency

Knee Osteoarthritis

(Xie et al, 2006, Knee Osteoarthritis)

 

Comparing knee OA between language groups:

 

 

Singapore English Version (n = 127)

 

 

KOOS Domain

Mean (SD)

Test-retest ICC

Pain

57.0 (16.0)

0.88

Symptoms

59.8 (19.1)

0.87

ADL

60.8 (16.9)

0.91

Sport & Rec

6.6 (12.2)

0.65

QOL

39.6 (18.8)

0.86

 

 

 

 

 

Singapore Chinese Version (n = 131)

 

 

Pain

57.3 (12.9)

0.87

Symptoms

63.2 (17.8)

0.85

ADL

62.2 (13.0)

0.84

Sport & Rec

4.8 (9.4)

0.78

QOL

42.9 (19.4)

0.60

Criterion Validity (Predictive/Concurrent)

Knee osteoarthritis:

(Thorund et al, 2010; n = 31; mean age = 46 (6) years; mean BMI = 26 (4) kg/m2; post surgery
21 (6) months; Danish sample, Knee osteoarthritis)

Patients versus control Knee Function:

  • Worse SF-36 Physical Functioning scores (p <0.001)
  • KOOS Activities of Daily Living score were significantly worse (p <0.001)
  • KOOS Sports Req scales were also significantly worse (p < 0.001)

Bibliography

Ahlden, M., Samuelsson, K., et al. (2012). "The Swedish National Anterior Cruciate Ligament Register: a report on baseline variables and outcomes of surgery for almost 18,000 patients." Am J Sports Med 40(10): 2230-2235. Find it on PubMed

Argenson, J. N., Parratte, S., et al. (2008). "Patient-reported outcome correlates with knee function after a single-design mobile-bearing TKA." Clin Orthop Relat Res 466(11): 2669-2676. Find it on PubMed

Bekkers, J. E., de Windt, T. S., et al. (2009). "Validation of the Knee Injury and Osteoarthritis Outcome Score (KOOS) for the treatment of focal cartilage lesions." Osteoarthritis Cartilage 17(11): 1434-1439. Find it on PubMed 

Engelhart, L., Nelson, L., et al. (2012). "Validation of the Knee Injury and Osteoarthritis Outcome Score subscales for patients with articular cartilage lesions of the knee." Am J Sports Med 40(10): 2264-2272. Find it on PubMed

Hill, G. N. and O'Leary, S. T. (2012). "Anterior cruciate ligament reconstruction: the short-term recovery using the Knee Injury and Osteoarthritis Outcome Score (KOOS)." Knee Surg Sports Traumatol Arthrosc. Find it on PubMed

Kvist, J., Ek, A., et al. (2005). "Fear of re-injury: a hindrance for returning to sports after anterior cruciate ligament reconstruction." Knee Surg Sports Traumatol Arthrosc 13(5): 393-397. Find it on PubMed

Lohmander, L. S., Ostenberg, A., et al. (2004). "High prevalence of knee osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury." Arthritis Rheum 50(10): 3145-3152. Find it on PubMed

Ornetti, P., Parratte, S., et al. (2008). "Cross-cultural adaptation and validation of the French version of the Knee injury and Osteoarthritis Outcome Score (KOOS) in knee osteoarthritis patients." Osteoarthritis Cartilage 16(4): 423-428. Find it on PubMed

Roos, E. M. and Dahlberg, L. (2005). "Positive effects of moderate exercise on glycosaminoglycan content in knee cartilage: A four‐month, randomized, controlled trial in patients at risk of osteoarthritis." Arthritis & Rheumatism 52(11): 3507-3514. Find it on PubMed

Roos, E. M., Roos, H. P., et al. (1998). "Knee Injury and Osteoarthritis Outcome Score (KOOS)--development of a self-administered outcome measure." J Orthop Sports Phys Ther 28(2): 88-96. Find it on PubMed

Roos, E. M. and Toksvig-Larsen, S. (2003). "Knee injury and Osteoarthritis Outcome Score (KOOS) - validation and comparison to the WOMAC in total knee replacement." Health Qual Life Outcomes 1: 17. Find it on PubMed

Salavati, M., Akhbari, B., et al. (2011). "Knee injury and Osteoarthritis Outcome Score (KOOS); reliability and validity in competitive athletes after anterior cruciate ligament reconstruction." Osteoarthritis Cartilage 19(4): 406-410. Find it on PubMed

Stevens-Lapsley, J. E., Schenkman, M. L., et al. (2011). "Comparison of self-reported knee injury and osteoarthritis outcome score to performance measures in patients after total knee arthroplasty." PM R 3(6): 541-549; quiz 549. Find it on PubMed

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