The effect of intra-articular injection of Diprospan at the knee joint on the hypothalamic-pituitary-adrenal axis

QUESTIONS UNDER STUDY: In this work we wanted to evaluate the effect of intra-articular injection (IAI) at the knee joint of 1 ml of Diprospan on the hypothalamicpituitary-adrenal (HPA) axis. METHODS: Consecutive patients attending the rheumatology or orthopaedic clinic with osteoarthritic knee pain not responding satisfactorily to medical and physical therapy were asked to participate in our study. After consent, patients had ultrasound-guided IAI of 1 ml of Diprospan, containing 2 mg of betamethasone sodium phosphate and 5 mg of betamethasone dipropionate. Demographic, clinical, laboratory and radiographic variables were documented. Just prior to the knee injection and 1, 2, 4 and 6 weeks later, patients had a 1-μg adrenocorticotropic hormone (ACTH) stimulation test. Secondary adrenal insufficiency (SAI) was defined as a poststimulation (30 minutes after ACTH injection) serum cortisol level of less than 18 μg/dl (∼500 nmol/ l) and lack of a rise of >6 μg/dl (∼166 nmol/l) over the basal level in poststimulation serum cortisol. RESULTS: Twenty patients completed the study. There were 3 male and 17 female patients, with a mean age of 58.6 ± 9.5 years. Six (30%) patients had evidence of SAI and in five of them it was seen at one time-point, mostly at week 2 after the IAI. In one patient, SAI was prolonged and observed from week 1 to week 4. CONCLUSIONS: IAI at the knee joint of 1 ml of Diprospan was associated with a transient high rate of SAI.