Many people turn to yoga as a way to exercise gently, as well as to reduce stress and improve flexibility. Yoga has other benefits for people with stiff joints due to arthritis as stretching exercises in general help improve range of motion, so the fact that you're tretching in yoga will help flexibility.
* Child's Pose (Balasana)
1) Sit on your heels on a yoga mat or on the floor.
2) Either keep your knees together or apart.
3) Slowly, bend forward by lowering your forehead to touch the floor, exhaling as you do so.
4) Keep your arms alongside your body. Make sure that your palms are facing up.
5) Alternatively, you can reach out your arms towards the front of the yoga mat, palms placed facing down on the mat.
* Tree Pose (Vrikshasana)
1) Keep your toes on the ground for better balance
2) Lean the heal on the erect leg. Or you can place your foot on the shin of the erect leg.
3) Once you are well balanced, take a deep breath in, gracefully raise your arms over your head from the side, and bring your palms together in ‘Namaste’ mudra (hands-folded position).
* Bridge Pose (Setu Bandhasana)
1) Get on your back, bend both knees and place the feet flat on the floor hip width apart. ...
2) Press the feet into the floor, inhale and lift the hips up, rolling the spine off the floor. ...
3) Press down into the arms and shoulders to lift the chest up
4) Breathe in and out for 4-8 breaths.