Knee Joint Damage
Due to its continual stepping motion, the Stairmaster is very hard on the knees. If you have a pre-existing condition, such as weak or injured knees, the Stairmaster is probably not for you. If you're completely new to exercise, you may want to start off with a milder cardiovascular workout and move on to the Stairmaster once your leg joints have been sufficiently strengthened. When in doubt, consult with your doctor.
Hip Joint Damage
The hip joints are in constant motion during a Stairmaster exercise. The up-and-down movement of the legs may aggravate hip injuries or weaknesses or even create new ones. It's best to vary your workouts to avoid hip pain and give your joints a rest (swimming is a great low-impact workout). Only use the Stairmaster at the level best suited to your abilities.
During a Stairmaster workout, your ankles support your entire body weight. This makes the workout effective, but overuse will hurt your ankles. Again, varying your cardiovascular workouts will give your ankles a much-needed break.
Balance and Posture Problems
A Stairmaster workout can cause back pain if you spend the entire workout leaning forward and "climbing" on the tips of your toes. Make an effort to maintain good posture throughout the workout to avoid this situation. The Stairmaster requires a significant amount of balance and should not be used by people with balance issues.
During an exhausting workout, it's tempting to grab the rails of the Stairmaster and hold on for dear life. However, consistent clutching of these rails can cause "Stairmaster wrist," or tendinitis, which is a painful inflammation of tendons caused by overuse. Rest your hands lightly on the rails if you need support, and don't hold on tightly. This has the added benefit of increasing the effectiveness of your workout.
Like any other machine, the Stairmaster runs the risk of having its parts fail. Most Stairmasters are cordless and run on a battery. If you're thinking of purchasing one, make sure that your purchase comes with a battery charger. There are many websites that sell Stairmaster replacement parts, such as sportsmith.net or fitnessrepairparts.com. If your machine is having problems, order online and climb some actual stairs until the replacement comes.