Literal meaning of yog or yoga is UNION. Krishna was the founder Yog Philosophy and its basics are first mentioned in Bhagwad Geeta. Rajyog, Gyanyog, Karmayog and Bhaktiyog are main forestays for achieving salvation. Patanjali further elaborated the Rajyog and Ashtnag Yog is the offshoot the same. So popular form yoga is not mere some physical exercise rather it is part of a philosophy with a most serious purpose. 
Yoga helps to control over mental faculties. It actually helps to maintain proper equilibrium between body, mind, intellect and supernatural powers. It also helps to relieve the body from various disorders which often afflict major chunk of human beings. It is a corrective, reformatory and holistic science for general well-being of body and mind.
In the West, yoga has been acknowledged more for its physical aspects whereas in India, it is a complete system of physical and mental training and a step forward towards spiritual enlightenment and self-purification.

Here is a list of asanas which are useful to cure a particular disease. The practitioner can perform and choose according to his need capacity and convenience. Asanas for most common diseases are  mentioned for individual diseases.