How long does a cortisone injection take to work for rotator cuff tendinitis?

The injection reduces inflammation around irritated shoulder tissues; it does not immediately repair a tendon. A local anaesthetic, if used, can make the shoulder feel better soon after the procedure, but that early change may fade before the cortisone has taken effect. Relief can be partial or temporary, and persistent pain may reflect tendon loading, weakness, or another shoulder problem.

Follow the clinician’s instructions about rest and movement. Avoid heavy lifting and painful overhead activity at first, then return gradually as discomfort settles. Gentle range-of-motion work may help prevent stiffness; strengthening is usually introduced in a planned way when the shoulder tolerates it. Do not use early pain relief as a reason to test the shoulder with strenuous activity.

Contact the treating clinic if pain is worsening rather than settling, the injection site becomes increasingly red or swollen, or you develop fever or feel unwell. Seek urgent help for severe breathing difficulty, facial swelling, or a rapidly spreading allergic reaction. Arrange review if useful relief does not develop within the timeframe your clinician gave you.

Ask when to restart exercises, which movements to avoid, what degree of soreness is expected, and what the next step should be if your shoulder remains painful.