Hi, Jane -
As long as you don't react to the salicylate acid in castor oil, go for it for as long as it works! It is historically an anti-inflammatory(see reference below).I have have seen some of the old mtn people here use castor oil, "horse liniment," skunk oil, and even WD-40! Most using the castor oil found some relief, but not over a long period of time. It will be interesting to see how long it works for you. Keep us posted on it!
I have heard of it being used for warts, hair replacement, & bruises in addition to the joint pain. All thru "home remedy" sources tho. And too, my grandmother use to give all of us kids a tablespoon of it when only one of us "acted up" - usually a boy cousin- while playing at her house. It tasted absolutely awful! I avoided her house when that particular cousin was there! Blaaaaaaah!
Are you sure it is osteo? Take a look here: http://www.merck.com/mmhe/sec05/ch067/ch067c.html
I have become highly sensitive to salicylate acid. I cannot even use my old standby, aloe, any more because of it.
I am going to try to cut and paste here, but I am not sure how to put info inside the little blue boxes yet!
----------From Wikipedia, the free encyclopedia:
Salicylic acid (from the Latin word for the willow tree, Salix, from whose bark it can be obtained) is a beta hydroxy acid (BHA) with the formula C6H4(OH)CO2H, where the OH group is adjacent to the carboxyl group. This colorless crystalline organic acid is widely used in organic synthesis and functions as a plant hormone. It is derived from the metabolism of salicin. It is probably best known as a compound that is chemically similar but not identical to the active component of aspirin.
Also known as 2-hydroxybenzoic acid, one of several beta hydroxy acids (compare to AHA), salicylic acid is a key ingredient in many skin-care products for the treatment of acne, psoriasis, calluses, corns, keratosis pilaris, and warts. It works by causing the cells of the epidermis to slough off more readily, preventing pores from clogging up, and allowing room for new cell growth. Because of its effect on skin cells, salicylic acid is used in several shampoos used to treat dandruff. Salicylic acid is also used as an active ingredient in gels which remove verrucas (plantar warts). Use of concentrated solutions of salicylic acid may cause hyperpigmentation on unpretreated skin for those with darker skin types (Fitzpatrick phototypes IV, V, VI), as well as with the lack of use of a broad spectrum sunblock.
The medicinal properties of salicylate, mainly for fever relief, have been known since ancient times, and it was used as an anti-inflammatory drug.
Aspirin (acetylsalicylic acid or ASA) can be prepared by the esterification of the phenolic hydroxyl group of salicylic acid.
Subsalicylate in combination with bismuth form the popular stomach relief aid known commonly as Pepto-Bismol. When combined, the two key ingredients help control diarrhea, nausea, heartburn, and gas. It is also a very mild antibiotic.
Although toxic in large quantities, salicylic acid is used as a food preservative and antiseptic in toothpaste. For some people with salicylate sensitivity even these small doses can be harmful.
Sodium salicylate is a useful phosphor in the vacuum ultraviolet with nearly flat quantum efficiency for wavelengths between 10 to 100 nm. It fluoresces in the blue at 420 nm. It is easily prepared on a clean surface by spraying a saturated solution of the salt in methanol followed by evaporation.
Salicylic acid has an ototoxic effect, and can induce transient hearing loss in zinc-deficient individuals.
This finding is based on clinical studies with rats. An injection of salicylic acid induced hearing loss in zinc-deficient rats, while a simultaneous injection of zinc reversed the hearing loss. An injection of magnesium in the zinc-deficient rats did not reverse the salicylic acid-induced hearing loss.
Salicylic acid is toxic in large amounts. Pregnant women are advised not to use products containing salicylic acid due to the danger of Reye's syndrome.
Some people are hypersensitive to salicylic acid and related compounds.
The United States Food and Drug Administration recommends the use of sun protection when using skincare products containing salicylic acid (or any other BHA) on sun-exposed skin areas. 
Salicylate sensitivity, also known as salicylate intolerance, is a chemical reaction that occurs when too much salicylate (salicylic acid) is introduced into a person's system. Salicylates are chemicals that occur naturally in plants and serve as a natural immune hormone and preservative, protecting the plants against diseases, insects, fungi, and harmful bacteria. Salicylate can also be found synthetically in many medications, perfumes and preservatives. This chemical can cause health problems in anyone when consumed in large doses. But, for those who are salicylate intolerant even small doses of salicylate can cause reactions. This reaction is different than a true allergy as it is a pharmacological reaction (like the side effects of a drug) and not an immunological reaction. People with salicylate sensitivity are unable to handle more than a certain amount of salicylates at a time without symptoms occurring.
Good luck with it! Symiere