Medical terms:
* Arthritis: Inflammation of one or more joints.
* Arthroscopy: A surgical procedure to examine the inside of a joint.
* Arthrodesis: Surgical fusion of a joint.
* Arthroplasty: Surgical replacement of a joint.
* Arthrology: The study of joints.
Other terms:
* Arthropod: An invertebrate animal with an exoskeleton, a segmented body, and jointed appendages. (Think insects, spiders, crustaceans)
* Arthromere: A segment of an arthropod's body.
* Arthrodial: Relating to a joint.
These are just a few examples. You can find many more words containing the root "arthro" by looking up medical dictionaries and general dictionaries.