With a knee injury, how would you safely get in and out of a bathtub?

Using certain device. Ther are very specific devices that can safely assist to accomplish this: bars, handles, specially made tubs, etc. The most important lesson here (for any health and safety issue is: don't do it alone. No worthwhile human endeavor was ever discovered or accomplished by being an island. Our society has to begin valuing human capiital, cooperation, connectivity, coordination, caring over the $ god!