For patients with disabling foot or ankle pain, medical or surgical treatment decisions can be difficult to make when multiple joints show changes of osteoarthritis or if the patient's pain clinically is related to a joint or tendon that is normal by other imaging studies. For these patients, injection of anesthetic, steroid, or both, into joints or tendon sheaths of the foot and ankle provides important diagnostic information and therapeutic relief. Diagnostic injections may show that the joints noted by other imaging studies have osteoarthritis that are not responsible for a patient's pain or that a normal joint is responsible. When multiple joints show changes of arthritis, anesthetic injections can help decide which and how many joints could benefit from surgical arthrodesis. Relief of pain after anesthetic joint injection correlates well with postoperative pain relief subsequent to arthrodesis. This article discusses the indications and the contraindications for performing diagnostic and therapeutic joint injections, and also presents the techniques for performing these studies.