Representative stabilograms indicating AP (y) and ML (x) excursions of COP. A: COP excursion of a patient who had left lower leg amputation. The correlation coefficient is Rxy = 0.75 (p <0.001). The regression line tends from the (left) prosthesis heel towards the right (intact) sole and the angle of regression line is a = 53°. B: COP excursion of a right leg amputee. The correlation coefficient is: Rxy = 0.72 (p <0.001) and the angle of regression line is a = -48°. The regression line trends from the (right) prostheses heel towards the left intact sole. The quadrants of the coordinate system are marked with numbers: 1, 2, 3 and 4.