High dosages of oral corticosteroids taken daily for prolonged periods of time can have serious systemic side effects including bone loss ( osteoporosis), increased risk of infections and diabetes and cataracts, thinning of skin, stretch marks, increased facial/body hair growth, acne, fluid retention, weight gain with redistribution of fat (fat deposits on back and face, thinning of limbs), muscle weakness, decreased resistance to infections, stomach ulcers, mood swings, insomnia, suppression of the body's own production of cortisol, etc.
How often cortisone injections are given varies based on the reason for the injection. This is determined on a case-by-case basis by the health care practitioner. If a single cortisone injection is curative, then further injections are unnecessary. Sometimes, a series of injections might be necessary; for example, cortisone injections for a trigger finger may be given every three weeks, to a maximum of three times in one affected finger. In other instances, such as knee osteoarthritis, a second cortisone injection may be given approximately three months after the first injection, but the injections are not generally continued on a regular basis.
However, a randomized, placebo-controlled, double-blind study by McAlindon et al found that in patients with knee osteoarthritis, intra-articular corticosteroid injections (40 mg of triamcinolone acetonide, administered quarterly over 2 years) led to an increase in cartilage loss and was associated with less pain reduction than placebo injections. The study determined that the mean change in index compartment cartilage thickness in the corticosteroid patients was about twice that of the placebo subjects. (The investigators stated, though, that due to the timing of pain measurements, the study could have missed transient pain reductions in the corticosteroid group.) [ 18 , 19 ]