We present a multifrequency, dense radio monitoring program of the blazar OJ287 using the 100-m Effelsberg radio telescope. The program aims to test different binary supermassive black hole (SMBH) scenarios and studying the physical conditions in the central region of this bright blazar. Between December 2015 and January 2017 (MJD 57370-57785), the radio electric vector position angle (EVPA) showed a large clockwise (CW) rotation by about 340{deg} with a mean rate of -1.04{deg}/day. Based on concurrent polarized Very Long Baseline Array (VLBA) data, the rotation seems to originate within the jet core at 43GHz. Optical polarization data show a similar monotonic CW EVPA rotation of about -1.1{deg}/day, superposed by shorter and faster rotations of about 7.8{deg}/day, mainly in the CW sense. When combined, the single dish, VLBI and optical polarization data are consistent with a polarized emission component propagating on a helical trajectory within a bent jet. We constrained the helix arc length (0.26pc) and radius (about 0.04pc) and the projected jet bending arc length (about 1.9-7.6pc). The helical trajectory covers only a part of the jet width, possibly its spine. In addition, we found a stable polarized component with EVPA (-10{deg}) perpendicular to the large scale jet, suggesting dominance of the poloidal magnetic field component.