Will deca or steroids that retain water help with tennis elbow? Cortizone (hydrocortisone) helped short term but is returning and effecting training again

Therapy is best. Steroid injections bring improvement 50% of the time at 6 weeks, but usually symptoms return. Subsequent injections buy less time and degree of relief. At 9 months and 1 year patient with therapy have been shown to fair the best, those with benign neglect the next best, and with steroids in third place. 90% of patients have resolution by 12 month. 10% require surgery.
Physical therapy. Tennis elbow can usually be treated by oral antiinflamatory medication or steroid inj. Pt in an essential part of a treatment plan. If that doesn't work, surgery is a last option.