Chemical exchange between water and exchangeable protons in macromolecules in knee cartilage can be quantified by fitting R1ρ dispersion data to a model. However, acquiring the entire dispersion curve is time consuming, which therefore hampers the application in clinical practice. We propose a simple three-point method for R1ρ dispersion data to estimate exchange rate. The method requires data acquired at three selected spin-locking frequencies instead of acquiring a full dispersion curve. The results show good agreement between the proposed method and measurements from the full dispersion data.