I do not believe that it prevents it. It is used to improve function and prevent re-injuring the tendons. Since TE is a repetitive stress (overuse) injury, you should probably not overdo the stretching when the TE pain or inflammation is really bad. RICE should be the initial treatment, Stretching comes a bit later.
It's not the elbow joint itself that needs stretching. It is forearm muscles & tendons that are stretched. For
TE, the tendons that attach some of the forearm muscles to the lateral epicondyle of the elbow have been compromised. (For GE, it's tendons that attach to the medial epicondyle). Note that the initial treatment phase of TE (and other inflammations) is
RICE.
Phase 2 includes stretching & strengthening - to return to function and to prevent re-occurrence. Check out Marius' (sticky) thread at the top of this forum for the treatment of TE and GE. To get you started on stretches & exercises, check out the following:
www.NISMAT.org/ptcor/tennis_elbow
.