MeSH is hierarchical, with broader and narrower terms. Take a look at the hierarchy for Low Back Pain.
Narrow results by selecting limits on the left-side menu of the results page. Click Show additional filters at the top of the menu to adjust your filters. Once filters are established, conduct your search, and then narrow results by clicking, for example, Humans and English, as shown below.
These links and short videos will help you get started with PubMed.
Select from the PubMed homepage the MeSH Database:
Learn to search with Medical Subject Headings ("MeSH") for a more focused search. Most articles have been assigned specific MeSH headings that reflect what major subjects the article is about. MeSH provides a consistent vocabulary so that you can search for the same subject.
If there is not a Medical Subject Heading for your topic, then use keywords.
Look at the example below. Librarian Tip: Once you find a relevant article, look at the Medical Subject Headings. It may help you find other articles on your topic.
Some PubMed Abstracts are constructed with specific fields to organize information: Study Design, Objective, Methods and Measures, Results and Conclusion