Answer:
Aerobic conditioning is incredibly valuable for cardiovascular health and wellbeing. Other activities that can help you break a sweat (increase your heart-rate for extended periods of time) would be biking (especially spin), swimming and yoga. Even fast walking would likely be ok - but if too painful, try using an insert in the heel (available at most drug stores). This shortens the length of the Achilles tendon and relieves some of the stress.
The key to a good aerobic work out is to shoot for a target heart rate of 220 minus your age and then multiply by 0.8 ({220 - age} x 80%). If you have trouble with the math - just work out hard enough so that you are not too out of breath and can speak at least five-word sentences comfortably. Maintain this workout for 45 mins and aim for five days weekly.