Since we are not medical practitioners we cannot provide a medical recommendation. Our advice is general in nature, based upon our experience. We suggest that you check with your physician prior to using the iWALK crutch.
With that being said, in our experience, success using the iWALK crutch when you have had a knee replacement is on a case-by-case basis. We have seen people with knee replacements that have no discomfort when using the iWALK crutch, but we've also seen people who cannot use the iWALK due to their knee replacement. There are unknown variables, so the only way to determine if you can adapt is to try it (with the consent of your physician). For now, you might try kneeling on a chair or stool for a few minutes to see if there is any discomfort attributable to your knee replacement.
Please note that you must be able to comfortably bend your injured leg at a 90-degree angle at the knee.