Gently dynamic repetitions help warm and loosen the joints to increase range-of-motion and decrease stiffness. The chair yoga practice and chair sun salutations/surya namaskar have helped people with back pain as well.Those who have arthritis that restricts their ability to get on the floor, please see all the gentle, restorative yoga asanas that can be done on the chair, bed, and standing found in links below. Standing positions may be helpful in improving balance and strengthening feet, ankles, knees, and hips.
Working for several years with seniors at our community center and seeing a range of issues, practical modifications have been made to adapt many asanas for the chair. Everything you need is on www.mahasriyoga.com/asana, www.mahasriyoga.com/pranayama, and www.mahasriyoga.com/meditation.
Other suggestion is Satyananda Yoga’s Pawanmuktasana Series Part 1 Anti-Rheumatic Group in Asana Pranayama Mudra Bandha. There will also be many suitable asanas in Swami Rama’s book Exercises for Joints and Glands.
Audio tracks on pranayama breathing and meditation form a complete practice. Studies suggest that these practices are helpful for arthritis, for a sense of well being, and an improved quality of life.