22 patients with osteoarthritis of the knee undergoing primary total knee arthroplasty (TKA) were randomized to receive a prehabilitation exercise program or a placebo training regimen. A significant treatment-by-time interaction was found for the Short Form-36 mental health scores, in which the prehabilitation group was superior to the control group at the end of the intervention, prior to surgery. There was no difference between the two groups at 6 and 12 weeks after surgery. No significant treatment-by-time interactions were seen for any other outcomes. However, large effect sizes were found for quadriceps strength and walking speed. This was a pilot study using a minimum amount of resources to replicate real-world prehabilitation settings.