Images of 2 mg/ml fluorescently spiked collagen gels before needling and after 2 revolutions. (A) Brightfield imaging of the gel with needle inserted before needling shows a small hole in an otherwise uniform field. (B) After needle rotation, the collagen fiber density appears to change around the needle. (C) Under cross-polars, the needle hole is again evident in an otherwise random field before needle rotation. (D) After rotation, the significant bright regions indicating collagen fiber alignment 45° off-axis. (E) Using confocal microscopy, the random orientation of collagen fibers is apparent. (F) After needling, the fiber density increases around the needle. Fibers near the needle are aligned circumferentially and transition to radial alignment away from the needle. Bars: A-D, 1 mm; E-F, 50 μm.