Apart from knowing the mechanics of your body, it is important to know your own body well to avoid injuries naturally. So, be aware of your body's strengths and limitations and take into consideration your physical weaknesses. More often than not, people injure themselves because they put too much pressure on a weak area of their body or overexert a weaker muscle.
For example, if you have knee problems, orthopedic surgeon Dr. Kenneth Plancher suggests that you should limit running on a treadmill or doing leg presses in the gym. It would be better to exercise on a stationary bike or elliptical machine to avoid damaging your knee joints further.
The same goes if you have any kind of back problems. You should make sure that you always lift objects properly, even if you don't think they are that heavy. To avoid injuring your back when lifting, you should stand with your feet slightly apart and one foot slightly forward to keep balance. Bend at your knees and firmly grip the object, keeping it as close as you can to your body. Lift the item from your hips, making sure that your back is always straight. Never lift from your back to avoid injuring yourself.