Use a combination of exercises instead of relying solely on ballet for fitness. Experts recommend cross-training to work the different muscle groups to prevent a knee injury.
Practice proper warm up techniques. This takes some of the pressure and strain off of your knees and gives the joints a chance to adjust to the motions.
Sleep eight hours every night. Dancers that are better rested are more likely to have stronger bodies, which helps them prevent all types of injuries to their bodies, including the knees.
Check your alignment when dancing to ensure that your knees stay properly aligned over your feet. Proper form reduces the strain on your knees and that in turn helps you prevent an injury.
Build up your knees by doing exercises that help stretch out that part of the body and increase the muscles. Some examples you can try include Pilates, yoga and low impact step aerobics.