To increase the strength of the fingers in the ability to abduct (splay outwards).
Place the affected hand by your side, elbow flexed and hand facing forwards. Thread the loops of a hand exerciser alldown to the middle of your fingers. If you don't have a hand exerciser then you can use your other hand to resist the movements of each successive finger.
Slowly and in a controlled manner fan your fingers outwards to reach the end of their limits and hold in that position for 5 seconds. Close your fingers together and repeat.
If both hands are affected, try the exercise with both hands simultaneously. If you suffer from connective tissue disease like rheumatoid arthritis ensure that you discuss this exercise with your osteopath.