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Table 1 Characteristics of the subjects and the study populations by MRI signal grade of menisci (N = 124)

From: Risk factors for lesions of the knee menisci among workers in South Korea’s national parks

Variables Number of subjects MRI signal grade of meniscia
Grade 0-1 Grade 2-3 P-value*
N % N (%) N (%)
General characteristics
Sex Male 116 93.5 48 (41.4) 68 (58.6) 0.361
Female 8 6.5 2 (25.0) 6 (75.0)
Age (year) <45 66 53.2 32 (48.5) 34 (51.5) 0.048
≥45 58 46.8 18 (31.0) 40 (69.0)
Body mass index (BMI) (kg/m2) <25 75 60.5 31 (41.3) 44 (58.7) 0.777
≥25 49 39.5 19 (38.8) 30 (61.2)
Smoking Never or past 32 25.8 11 (34.4) 21 (65.6) 0.426
Current 92 74.2 39 (42.4) 53 (57.6)
Alcohol drinking <1 times/week 64 51.6 23 (35.9) 41 (64.1) 0.304
≥1 times/week 60 48.4 27 (45.0) 33 (55.0)
Regular exercise Once a week or more 109 87.9 46 (42.2) 63 (57.8) 0.250
Less than once a week 15 12.1 4 (26.7) 11 (73.3)
Leisure activityb No 47 37.9 22 (46.8) 25 (53.2) 0.250
Yes 77 62.1 28 (36.4) 49 (63.6)
Previous exercise-related knee injury No 90 72.6 37 (41.1) 53 (58.9) 0.771
Yes 34 27.4 13 (38.2) 21 (61.8)
Previous accident-related knee injury No 78 62.9 36 (46.2) 42 (53.8) 0.085
Yes 46 37.1 14 (30.4) 32 (69.6)
Previous work-related knee injury No 61 49.2 29 (47.5) 32 (52.5) 0.107
Yes 63 50.8 21 (33.3) 42 (66.7)
Previous knee pain No 22 17.7 11 (50.0) 11 (50.0) 0.308
Yes 102 82.3 39 (38.2) 63 (61.8)
Past medical historyc No 86 69.4 39 (45.4) 47 (54.6) 0.086
Yes 38 30.6 11 (28.9) 27 (71.1)
Occupational characteristics
Overtime labor No 23 18.5 9 (39.1) 14 (60.9) 0.897
Yes 101 81.5 41 (40.6) 60 (59.4)
Holiday use Yes 119 96.0 48 (40.3) 71 (59.7) 0.988
No 5 4.0 2 (40.0) 3 (60.0)
Physical burden of workd Low 101 81.5 42 (41.6) 59 (58.4) 0.548
High 23 18.5 8 (34.8) 15 (65.2)
Stair flighte No 92 74.2 41 (44.6) 51 (55.4) 0.103
Yes 32 25.8 9 (28.1) 23 (71.9)
Kneelingf No 100 80.6 41 (41.0) 59 (59.0) 0.754
Yes 24 19.4 9 (37.5) 15 (62.5)
The cumulative intensity of trekking 1 <17 years 67 54.0 34 (50.8) 33 (49.2) 0.010
(= Tenure) ≥17 years 57 46.0 16 (28.1) 41 (71.9)
The cumulative intensity of trekking 2g Low 40 32.3 21 (52.5) 19 (47.5) 0.019
Medium 55 44.3 22 (40.0) 33 (60.0)
High 29 23.4 7 (24.1) 22 (75.9)
The cumulative intensity of trekking 3h Low 42 33.9 23 (54.8) 19 (45.2) 0.006
Medium 65 52.4 24 (36.9) 41 (63.1)
High 17 13.7 3 (17.6) 14 (82.4)
MRI scan area Left knee 59 47.6    
Right knee 60 48.4    
Both knees 5 4.0    
MRI signal grade of meniscii 0 36 29.0    
1 14 11.3    
2 57 46.0    
3 17 13.7    
Location of menisci tear No menisci tear 50 40.3    
Lateral 22 17.8    
Medial 52 41.9    
Site of menisci tear No menisci tear 50 40.3    
Anterior horn 11 8.9    
Body of menisci 5 4.0    
Posterior horn 58 46.8    
Type of menisci tear No menisci tear 50 40.3    
Longitudinal 0 0.0    
Radial 29 23.4    
Horizontal 43 34.7    
Complex 2 1.6    
  1. aGrading system based on the MRI signals decribed by Crues et al.
  2. bLeisure activities requiring physical activity, Two or more times per week
  3. cRheumatoid Arthritis, Diabetes, Lupus disease, Gout, Osteoporosis, Menopause, Osteoarthritis, etc
  4. dLow : tolerable workload, High : intolerable workload
  5. eLast month an average of two more steps (36 cm) jump down the stairs at least 20 times for a day
  6. fMore than 2 h a day for 1 month average
  7. gcalculated with trail distance, employment period, trekking times
  8. hcalculated with trail distance, employment period, trekking times, trail difficulty
  9. iAll menisci were graded according to Crues JV II et al.: grade 0, no high signal in the menisci; grade 1, irregular type of high signal in the menisci; grade 2, linear type of high signal in the menisci; grade 3, extension of high signal to the margin of the menisci
  10. * P-value by chi-squared test