as you know the cartilage
or gliding surface in the joints of patients with achondroplasia
is abnormal and does wear out sooner than in people who do not have this health problem. your wife should still however have her elbow assessed with an XR and possibly an MRI
and CT scan
as this may show a treatable problem in the elbow that could help with her symptoms. in the mean time she could use some antinflammatory medication and go to see a physiotherapist.