Walk on an incline
If you’re indoors, a treadmill will allow you to manipulate your incline which can enhance the caloric burn of your walk. If you’re outside, try to opt for a hilly area to optimize your walk. Research suggests that increasing the incline can enhance the intensity of the workout while also reducing the impact on the legs and joints. Plus, it activates many muscles throughout your body including your legs and core, while also increasing cardiovascular stamina and calorie burn. 
Sprinkle in some reverse walking
Reverse walking, a fancy way to say walking backwards, may sound silly but it actually provides a variety of health benefits. It can help enhance body coordination and increase strength in leg muscles that are not as heavily used. A recent study even found that backwards walking reduced pain and improved physical function in individuals with knee osteoarthritis. Try doing a short burst of reverse walking a few times throughout your walk, just be sure to stay aware of your surroundings.