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Table 2 Mean annual change of clinical variables in groups according to final knee flexion after TKA

From: A high degree of knee flexion after TKA promotes the ability to perform high-flexion activities and patient satisfaction in Asian population

Variable Estimated marginal mean (95% CI) Mean change/year (95% CI) p for interaction with time
Preoperative
(n = 912)
2 years
(n = 912)
5 years
(n = 718)
10 year
(n = 261)
linear quadratic linear quadratic
Knee flexion (°)
 Final knee flexion < 130 119.5 (114.6, 124.3) 123.0 (118.2, 127.8) 124.7 (119.8, 129.6) 118.2 (112.5, 123.8) 2.2 (1.6, 2.9) −0.2 (− 0.3, − 0.2) 0.006 0.023
 Final knee flexion ≥130 131.4 (126.6, 136.2)*** 134.6 (129.8, 139.3)*** 137.3 (132.5, 142.1)*** 136.6 (131.5, 141.7)*** 1.9 (1.4, 2.3) −0.1 (− 0.2, − 0.1)
Flexion contracture (°)
 Final knee flexion < 130 10.4 (8.2, 12.5) 3.3 (1.2, 5.4) −2.1 (−4.2, 0.0) 2.8 (0.4, 5.2) −4.2 (− 4.5, −3.9) 0.4 (0.3, 0.4) n.s. n.s.
 Final knee flexion ≥130 9.7 (7.6, 11.7) 3.2 (1.1, 5.2) −1.9 (−4.0, 0.2) 2.0 (−0.2, 4.2) −3.9 (− 4.1, − 3.7) 0.3 (0.3, 0.3)
Range of motion (°)
 Final knee flexion < 130 107.7 (100.2, 115.2) 117.4 (109.9, 124.8) 124.0 (116.5, 131.6) 114.3 (105.6, 123.1) 5.9 (4.8, 7.0) −0.5 (− 0.7, − 0.4) n.s. 0.028
 Final knee flexion ≥130 119.5 (112.1, 126.9) 127.7 (120.4, 135.1) 134.8 (127.4, 142.2) 132.5 (124.6, 140.4)** 4.8 (4.1, 5.5) −0.4 (− 0.4, − 0.3)
Knee Society score
 Final knee flexion < 130 58.9 (52.4, 65.5) 85.7 (79.3, 92.1) 105.9 (99.4, 112.4) 86.2 (78.5, 94.0) 16.1 (15.0, 17.1) −1.3 (− 1.5, − 1.2) n.s. n.s.
 Final knee flexion ≥130 59.2 (52.7, 65.6) 85.9 (79.6, 92.3) 106.2 (99.8, 112.6) 86.9 (80.1, 93.8) 16.0 (15.3, 16.7) −1.3 (− 1.4, − 1.3)
Knee Society function score
 Final knee flexion < 130 50.3 (40.3, 60.3) 73.0 (63.2, 82.9) 87.2 (77.2, 97.3) 57.7 (45.9, 69.5) 14.0 (12.7, 15.4) −1.3 (− 1.5, − 1.2) 0.007 n.s.
 Final knee flexion ≥130 50.7 (40.8, 60.6) 73.5 (63.6, 83.3) 90.1 (80.2, 100.0) 71.0 (60.4, 81.5) 13.7 (12.9, 14.6) −1.2 (− 1.3, − 1.1)
Hospital for Special Surgery score
 Final knee flexion < 130 63.7 (57.5, 69.9) 83.8 (77.6, 89.9) 97.9 (91.7, 104.1) 78.8 (71.5, 86.0) 12.2 (11.4, 13.0) −1.1 (− 1.2, − 1.0) 0.029 n.s.
  Final knee flexion ≥130 64.1 (58.0, 70.2) 84.7 (78.7, 90.8) 100.2 (94.1, 106.3) 84.8 (78.3, 91.3) 12.4 (11.8, 12.9) −1.0 (− 1.1, − 1.0)
WOMAC (total)
 Final knee flexion < 130 39.9 (32.6, 47.1) 19.9 (12.7, 27.0) 4.9 (−2.4, 12.1) 20.0 (11.9, 28.1) −12.0 (− 13.0, − 11.1) 1.0 (0.9, 1.1) 0.003 n.s.
 Final knee flexion ≥130 40.7 (33.5, 47.8) 18.8 (11.7, 26.0) 1.8 (−5.4, 8.9) 15.0 (7.5, 22.5) −13.0 (− 13.6, − 12.4) 1.0 (1.0, 1.1)
WOMAC (pain)
 Final knee flexion < 130 6.4 (5.1, 7.6) 2.1 (0.9, 3.4) −1.3 (−2.5, −0.0) 1.0 (−0.4, 2.4) − 2.5 (− 2.7, − 2.3) 0.2 (0.2, 0.2) n.s. n.s.
 Final knee flexion ≥130 6.6 (5.4, 7.8) 2.1 (0.9, 3.3) − 1.5 (− 2.7, − 0.3) 1.1 (− 0.2, 2.4) −2.7 (− 2.8, − 2.6) 0.2 (0.2, 0.2)
WOMAC (stiffness)
 Final knee flexion < 130 3.2 (2.5, 3.9) 1.4 (0.7, 2.1) 0.0 (− 0.7, 0.7) 1.0 (0.2, 1.8) −1.1 (− 1.2, − 1.0) 0.1 (0.1, 0.1) n.s. 0.027
 Final knee flexion ≥130 3.3 (2.6, 4.1) 1.3 (0.6, 2.0) −0.2 (− 0.9, 0.5) 1.1 (0.4, 1.8) −1.2 (− 1.3, − 1.1) 0.1 (0.1, 0.1)
WOMAC (physical function)
 Final knee flexion < 130 30.8 (24.9, 36.6) 16.2 (10.5, 21.9) 5.7 (−0.1, 11.5) 18.6 (12.0, 25.2) −8.8 (−9.6, −8.0) 0.76 (0.67, 0.85) 0.001 n.s.
 Final knee flexion ≥130 31.0 (25.3, 36.7) 15.2 (9.5, 20.9) 3.0 (−2.7, 8.7) 13.3 (7.3, 19.3) −9.4 (−9.9, −8.9) 0.77 (0.71, 0.82)
  1. WOMAC Western Ontario and McMaster Universities Osteoarthritis Index, n.s. not significant
  2. ***, p < 0.001; **, p < 0.01; *, p < 0.05, compared two group at each point