I believe you have two options.
Option #1 is to code this as M16.0 based on the radiology report. Per the AHA coding clinic & ICD-10 coding handbook, when the type of osteoarthritis is not specified, 'primary' is the default.
Option #2 is to query the provider and ask if the osteoarthritis is due to or associated with the patient's Acromegalia. The provider states the pain may be due to the Acromegalia. The phrase 'may be' indicates an assumption. As outpatient coders, we cannot code diagnoses documented as "probable", "suspected", "questionable", "rule out", or "working diagnosis" or other similar terms indicating uncertainty (per ICD-10 guidelines pg 30 H.). It would be incorrect to code this as osteoarthritis due to or associated with Acromegalia based on the current documentation which states the pain 'may be' due to the Acromegalia.