My wife is 55 years old , is 5ft91/4inches tall and weighs about 170lbs she wants to start jogging and I cautioned her against it as taller and heavier people appear to have a higher risk of knee/leg injuries than shorter light people. I suggested power walking as a substitute and would like to know if my caution was warranted?
As @Raditz_35 stated, she's below the average height (and weighs about the same if not less) of men and there are a lot of men who jog just fine.
To put it into perspective, I'm 5'11" and weigh 250 lbs (mostly fat for now) and I jog about 3-5 times a week with hardly any joint pain. That said, this is an anecdotal point so take with a grain of salt.
I've never heard of taller people at risk of injury when running, but have heard of heavier people are more at risk, but that caveat is usually for obese people (people with a BMI of 30 or higher) whereas your wife has a BMI of about 25.1, she's barely in the overweight category. If in doubt, seek medical consult as they can tell you if running is too risky. They may even point you in the right direction for better exercises.
Off the top of my head, good alternatives are cycle machines, ellipticals, and swimming. Those three are low impact on the joints.