Often as you perform a search on Discover, you may find Influencers that may not be specific enough for your requirements. You can narrow down your influencer search by Location (country), Audience Size (Reach), Role, Gender, Field, Persona & Account Type. For each of these, you can specifically include or exclude a particular group - including influencers with a reach under 100,000 but excluding those from the USA, for example.
A search for "Knee Pain Healthcare Professionals" can be narrowed down by adding a filter for roles to cut down on results around food blogs. To do so, perform a search and click "show filters", which will expand a menu;
If Role is not present then add it on the left side by clicking on the box on the lower left, add the tag "Healthcare Professionals" as shown on the lower middle box. Hit the search button to refresh the search with the newly applied filter and the results will be updated as shown below.