Orthopedic Coding Alert

Question: I am new to orthopedic coding; only on the job six months. One of the more difficult conditions I’ve found to diagnose is osteoarthritis (OA). I’m unsure of the difference between primary, post-traumatic, and secondary OA in the M19.- (Other and unspecified osteoarthritis) code set. Can you walk me through the best way to choose among these ICD-10 codes?

RCI Subscriber

Answer: Choosing OA ICD-10 codes can get tricky even for the most seasoned coders, as there are several elements you’ll need to consider when choosing the correct diagnosis code. Follow this quick primer to find the right OA diagnosis code every time.

First, you should know some basic definitions.

Primary OA occurs due to uneventful depreciation; it’s just normal wear-and-tear. “Secondary OA is caused by a known reason or consequence,” explains Kaitlyn Bohrer, CPC, COSC, orthopedic surgery coder at Eastside Orthopedics & Sports Medicine in Oregon. “A primary condition or diagnosis you may find attached to secondary OA is mostly contributory to underlying conditions such as obesity, genetics, inactivity, and a large inventory of other diseases.” 

Post-traumatic OA is a sub-type of secondary OA. “Just as it sounds, post-traumatic arthritis is contributory to a particular trauma or injury such as a subsequent fracture to a bone after playing a sport or an injury due to a car accident,” Bohrer explains.

More on M19.-: You’ll need to change gears when reporting M19.- codes, as they differ from the OA codes that precede them: M15 (Polyosteoarthritis) through M18.- (Osteoarthritis of first carpometacarpal joint) all contain codes for primary and post-traumatic OA, but these are also represented again in M19.-.

First, you’ll choose the OA type: primary (M19.0-), post-traumatic (M19.1-), secondary (M19.2-), or unspecified (M19.9-). If it’s one of the first three OA types, you’ll then choose a 4^th character to represent anatomic location and a 5^th character to represent laterality. If, however, the OA is unspecified (M19.9-), you’ll only choose a 4^th character to represent OA type.

Chris Boucher, MS, CPC, Senior Development Editor, AAPC