Yoga is safe form of exercise which stretches and strengthens back muscles and helps maintaining the natural curve of our spine, thereby reducing the back or joint pain.
Backache is one of the most common medical condition. It can have many reasons-
1- Pulled muscle or tendon-can happen due to lifting heavy objects or working out or sleeping in awkward position.
2- Inflammation– can be because of some injury or disease. 
3- Arthritis is a type of chronic inflammation affecting mainly joints of our body including our back. It is associated with stiffness and swelling and pain.
4- Osteoporosis– is a disease where bone mass is decreased and makes bones weak and that can lead to painful fractures.
5- Stress– Poor posture and overweight can cause extra stress on Spine and our back muscles have to work extra hard, cause of which  aching in back happens.
6- Slipped disc– The soft tissue in the discs between joints has come out due to wear and tear which causes pain in lower back.
7- In women pregnancy, childbirth, hormonal disbalance, weight gain, can lead to back pain

CURE –

• Keep moving
•stretching and strengthening of muscles, •keep good posture.

Yoga helps in stretching and strengthening both sides of the body equally. Proper body alignment and good posture helps maintaining natural curvature of the spine which is important part of reducing or avoiding lower back pain.
Practicing yoga postures can help in reducing and curing back pain –
• Marjariasana(cat/cow pose)
•Cobra pose
• Locust pose
• Paschimottanasana
• Bridge pose
• Mountain pose
• Forward bending pose
• Shashank Aasana
•Trikonasana