The possible reasons for an elbow pain
The elbow is made up of three joints: the first, the humeroulnar, or trochlea, works a bit like a hinge to allow bending and straightening (flexion and extension) of the forearm; the second is the humeroradial, which allows the forearm to rotate the wrist (supination and pronation) and stabilizes the elbow. The third is the proximal radioulnar, which is the rolling of the radius on a tiny lateral facet of the ulna (necessary for supination and pronation)
Elbow osteoarthritis is fairly rare, but issues with tendons (of the biceps and epicondyles) are frequent. If we exclude injuries, the most frequent problems are bursitis (the bursa on the olecranon often being the site of inflammation) and tendon tears (particularly the distal biceps).