Table 2. Mean absolute and percent 4-year longitudinal change (and 95% confidence interval) of thigh muscle cross-sectional areas, isometric muscle strength and specific strength in chronically painful versus painless knees.
| Chronically painful (n=43) | Within group p* | Painless (n=43) | Within group p* | Difference in absolute change | Difference in % change | Between group p# | |||
|---|---|---|---|---|---|---|---|---|---|
| Absolute change | % change | Absolute change | % change | ||||||
| Anatomical cross-sectional areas (cm2) | |||||||||
| Quadriceps | -2.14 (-3.37, -0.92) | -3.9 (-6.3, -1.5) | 0.001 | -1.33 (-2.28, -0.39) | -2.4 (-4.1, -0.7) | 0.007 | -0.81 (-2.48, 0.86) | -1.5 (-4.8, 1.8) | 0.33 |
| Quad%TTC | -1.26 (-1.72, -0.81) | -4.8 (-6.6, -3.1) | <0.001 | -0.22 (-0.67, 0.24) | -0.8 (-2.4, 0.8) | 0.34 | -1.05 (-1.71, -0.39) | -4.0 (-6.5, -1.5) | 0.003 |
| V. medialis | -1.17 (-1.71, -0.62) | -5.8 (-8.6, -3.0) | <0.001 | -0.49 (-0.86, -0.11) | -2.1 (-3.9, -0.3) | 0.01 | -0.68 (-1.25, -0.11) | -3.7 (-6.6, -0.9) | 0.02 |
| V. lateralis | -0.35 (-0.87, 0.17) | -2.2 (-6.3, 1.9) | 0.18 | -0.19 (-0.61, 0.24) | -0.4 (-3.8, 2.9) | 0.39 | -0.17 (-0.89, 0.56) | -1.7 (-7.8, 4.3) | 0.64 |
| V. intermedius | -0.44 (-0.86, -0.02) | -2.8 (-5.7, 0.1) | 0.04 | -0.29 (-0.57, -0.01) | -2.1 (-4.1, 0.0) | 0.04 | -0.15 (-0.69, 0.39) | -0.7 (-4.5, 3.1) | 0.58 |
| Rectus femoris | +0.04 (-0.20, 0.28) | +2.7 (-6.5, 11.9) | 0.73 | -0.07 (-0.20, 0.06) | -2.7 (-8.1, 2.7) | 0.31 | +0.11 (-0.18, 0.39) | +5.4 (-6.1, 16.8) | 0.45 |
| Hamstrings | -1.75 (-2.59, -0.91) | -4.1 (-6.2, -1.9) | <0.001 | -1.17 (-1.79, -0.56) | -3.4 (-5.1, -1.6) | <0.001 | -0.57 (-1.46, 0.31) | -0.7 (-3.1, 1.7) | 0.20 |
| Adductors | +0.44 (-0.63, 1.52) | +7.7 (-1.1, 16.5) | 0.41 | +0.04 (-0.54, 0.63) | -0.1 (-5.2, 5.0) | 0.88 | +0.40 (-0.82, 1.63) | +7.8 (-2.5, 18.1) | 0.51 |
| Total muscle | -3.47 (-5.90, -1.05) | -2.9 (-5.2, -0.7) | 0.01 | -2.53 (-4.32, -0.74) | -2.4 (-4.2, -0.7) | 0.007 | -0.95 (-4.02, 2.13) | -0.5 (-3.4, 2.5) | 0.54 |
| Total thigh | +1.70 (-3.34, 6.73) | +1.2 (-1.6, 4.0) | 0.50 | -2.63 (-6.54, 1.28) | -1.4 (-3.5, 0.7) | 0.18 | +4.33 (-2.08, 10.7) | +2.6 (-0.9, 6.1) | 0.18 |
| Strength (Newton) | |||||||||
| Extensors | -25.6 (-56.1, 4.91) | +5.5 (-15.3, 26.4) | 0.10 | -22.7 (-49.3, 3.86) | 0.0 (-11.0, 11.0) | 0.09 | -2.86 (-45.5, 39.8) | +5.5 (-18.9, 30.0) | 0.89 |
| Flexors | -16.4 (-31.3, -2.36) | +0.2 (-14.3, 14.6) | 0.02 | -30.8 (-45.4, -16.3) | -10 (-25.9, 5.3) | <0.001 | 14.0 (-7.03, 35.0) | +10 (-12, 33) | 0.19 |
| Specific Strength (Newton/cm2) | |||||||||
| Extensors/Quad | -0.15 (-0.84, 0.53) | +9.6 (-11.4, 30.7) | 0.66 | -0.31 (-0.81, 0.20) | +2.7 (-9.2, 14.6) | 0.23 | +0.15 (-0.74, 1.05) | +6.9 (-18, 32) | 0.73 |
| Flexors/Ham | -0.22 (-0.63, 0.19) | +5.1 (-10.4, 20.7) | 0.28 | -0.78 (-1.19, -0.38) | -6.9 (-23.9, 10.0) | <0.001 | +0.56 (-0.01, 1.13) | +12 (-12, 37) | 0.06 |
Quad%TTC=percentage of quadriceps of the total thigh cross-sectional area; V.=Vastus; specific strength = isometric strength divided by muscle cross sectional area; Extensors/Quad=Extensors/Quadriceps; Flexors/Ham=Flexors/Hamstrings;
*
paired t-test for change over four years;
#
paired t-test comparing change in painful with that in painless knees