Many recreational tennis players have suffered at one time or another from Tennis Elbow, soreness and/or inflammation at the tendon connection of the wrist extensor muscles, to the outside of the upper arm bone at the elbow. (The Lateral Epicondyle)
It is not restricted to tennis players and a number of people involved in other activity from carpenters to politicians suffer. Can you identify any actions at the wrist that might be common to all of these people involved in different activities.

Establishing a common cause in each individual case is difficult and at this stage not particularly helpful, but the symptom is easier to describe.
The wrist extensor muscles are under more stress than they are able to handle in a particular movement, the result of which is damage to the tendon connection to the upper arm bone. (lateral epicondylitis )

A functional assessment might reveal any from a number of causes in each individual case, ranging from dysfunction in the foot and ankle, or the hip or right up through the trunk to the neck. If this surprises you see (All human movement is a chain reaction)

But this does not help you to understand or avoid tennis elbow.

You can, in the first instance, start to address a problem common among recreational players which may alleviate this condition (see below)

The common action I asked you to think about in paragraph 1 is the firm grasping of an object. See Quote from Gray Institute
(The biomechanics that is common to all of these scenarios is the firm grasping of an object. When the finger flexor muscles contract to grab something, these muscles will also flex the wrist. The wrist flexion is not desired and will actually weaken the grip. So the wrist extensors must contract to offset/negate the wrist flexion.)

So a firm grip creates stress which is compounded by the additional stress of impact between racket and ball at contact.
My clients will tell you they have the words “ loosen that grip” and “spread the fingers on the handle” gently ringing in their ears, all of the time.
As a CAFS qualified movement specialist I can assess the other likely causes in your whole body movement and subsequent arm action. I can address technical problems and recommend specific functional exercises to address visible chain dysfunction, which should alleviate symptoms and aid recovery.
You need to consult your medical practitioner before starting any new exercise problem.

Contact me today for your free half hour assessment if you live in the Mole Valley district.
If you live further afield contact me to discuss your condition.