Essential Oils for circulation, muscle and joints.

Essential oils should never be applied directly to the skin or ingested.They should be diluted in a suitable carrier oil such as grapeseed, sweet almond, olive , jojoba, or sunflower oil before they are applied to the skin. Take note of any contra-indications with specific safety data before using a new oils, especially with regard to toxicity levels, photoxicity, dermal irritation and sensitization.  For example fennel, hyssop and sage should be avoided by epileptics. Clary sage should not be used whilst drinking alcohol; hops should not be used by anyone suffering from depression.
Personally I would not use any essential oils on a pregnant woman or a breastfeeding woman, a massage if needed can be carried out using just a carrier oil. The reason being is that the molecules of an essential oil are small enough to pass through the skin and they enter the bloodstream. With babies and children always err on the side of caution. For babies 0-12 months the dose per oil is 1 drop of essential oil to 1 tsp carrier oil for massage or bathing. "Safe" oils(non toxic and non irritant to the skin) that can be used for babies and children are lavender, rose, and chamomile.
Infants it 1-5 years use 2 to 3 drops of safe essential oils to 1 tsp.
Children 6-12 years, use half the amount as stated for adults.
Over 12 years as directed for adults.
For an adult a usual ratio of essential oils to carrier oils  is 4-6 drops per 10 ml of carrier oil for a back massage and 4-6 drops per 20ml of carrier oil for a  full body massage.
The essential oil should be allowed to drop into the container first without shaking the bottle to get an accurate measurement, and if you are using a blend of two oils or more, the amount is the same but divided between them. Never exceeding 4-6 drops combined.  The oils will create a synergy ( a different oil) when allowed to mix in the container, you then add the carrier oil.
Essential oils that are good for arthritis and rheumatics are black pepper, ginger, lavender, turmeric and lemon. Such oils can relieve local inflammation by setting free mediators in the body which in turn cause the blood vessels to expand, so the blood is able to move more quickly and the swelling is reduced.