Magnetic helicity is an invariant of the ideal MHD equations and is used as a diagnostic tool in the analysis of magnetic fields in active regions. Here, we explore an associated quantity, the winding number, that measures the degree of knotedness of a magnetic field configuration. The winding has the advantage of not being strongly concentrated in regions of strong magnetic field, and therefore it is more sensitive to changes in the topology of the magnetic field in the whole domain. The winding has been shown to be an efficient tool in MHD simulations of magnetic field emergence, now we present evidence of its efficacy in observations. We present the analysis of a few active regions using the winding and compare it with the analysis of helicity. In summary, we find that the winding is able to detect structural changes in the magnetic field more effectively than the helicity, and suggest that it can be used as an alternative predictive tool for eruptive events in active regions.