A method of treating a patient for a disease, such as arthritis, is described. Steps include treating an animal for the disease with a first treatment, capturing video frames, then using optical flow to compute vector fields for each frame, then taking a maximum vector value over a first time period, then selecting a set of maximum vector values over a second time period, then clipping those values to a maximum, and then computing an average of those values. This value is an efficacy and it is compared to a baseline efficacy. If the treatment is efficacious, the patient is so treated. A method of applying for a drug for approval is also described, using substantially the same steps.