Tennis elbow and golfer's elbow are common but not good synonyms for lateral and medial epicondylitis at the elbow.
Pain on use occurs around the area of insertion of the relevant group of muscles of the forearm into the bone of the humerus and the membrane between the flexor and extensor muscles of the upper arm. It tends to nag on.
Altering the alignment of the muscles and ligaments, by a clasp worn around the area pressing on the painful point or in extremis by orthopaedic surgical intervention may help. Injection is often used and the pain sometimes resolves after it. Steroids, sodium hyaluronate, botulinum toxin and prolotherapy seem to work. A problem is that long term outcome is worse after steroid injection even though both injector and customer are happy with the short term benefit.