ICD-10 Reminder Series: Chapter 1.C.13 Disease of the Musculoskeletal System

ICD-10 Reminder Series: Chapter 1.C.13 Disease of the Musculoskeletal System

Posted by Julie McLaws
Jul 30, 2019 11:00:00 AM

Chapter 13: Diseases of the Musculoskeletal System and Connective Tissue can be a daunting chapter for many coders, but with an understanding of what the chapter includes, attention to detail, and a few tricks, it’s very doable. So let’s dig in.

Most of the codes found within this chapter include site and laterality designations.


  • Site = Which bone, joint or muscles are involved
  • Laterality = Placement on the body - right, left, or unspecified

There will be times that a “multiple sites” code will be available, and there will be other times where multiple codes must be used to accurately represent the condition. (ICD-10-CM Guideline 1.13.A)

According to ICD-10-CM Guidelines 1.13.B. this chapter includes “musculoskeletal conditions [that] are a result of previous injury or trauma to a site or are recurrent conditions.” Note, this does not include current, acute injuries which will most often be found in chapter 19, and the code will begin with an ‘S ’ or ‘T ’. At times it can be difficult to differentiate from the documentation whether the condition is acute or chronic and would be appropriate to query the provider for additional information.

Next, it’s crucial to start with the ICD-10 codebook Index. This step is so basic, but because of its simplicity, many coders will skip it thinking they can instead flip through the tabular chapter and somehow land on the correct code, but this will rarely be successful. After a successful search of the index, then it will be time to work through the tabular.

Practice Makes Perfect

Let’s work through practice coding an initial pathological fracture of the left femur.

First things first, the definition of “pathological,” according to the Merriam-Webster dictionary, means “altered or caused by disease” so we know that this is not an acute condition and our final code will be found in chapter 13.

In the Index go to Fracture, pathological. Notice what the next words state (see also Fracture, traumatic). It’s important to note that traumatic = acute; this would be an injury, and if this path were followed in the index, the final code would be found in chapter 19 and would be incorrect coding of a pathological fracture.

Next, look for Femur. Which gives the code M84.45. This is correct, right? Not quite. Note the little check mark next to M84.45ü – this means the final code requires additional characters. This knowledge comes from the key to symbols, which in my ICD-10 book is found at the bottom of the page. Next, we will turn to the tabular index to find:

M84.45 Pathological fracture, femur, and pelvis

M84.452 Pathological fracture left femur

But don’t stop there! Note that the code requires a 7th character. It is always a good practice when maneuvering through the ICD-10 book to read the section header of a chosen code for additional information such as Excludes 1 and 2 notes, and additional character information. For this code, the appropriate 7th character is found right under M84.4. Since we are looking for a pathological femur of the left femur, initial encounter; we know that the final correct code is M84.452A

To recap, when coding from Chapter 13: Diseases of the Musculoskeletal System and Connective Tissue; first, understand the diagnosis you are coding. Know if it stems from another condition, is a recurrent condition, or perhaps is an injury that needs to be approached differently. Next, use your index and pay special attention to additional information given. Finally, visit the code in the tabular chapter to double check yourself and ensure you are capturing the specific code requirements.

Using these tips and the knowledge found in the ICD-10 Guidelines you will be able to easily and accurately capture the musculoskeletal conditions all of the time.

Questions or Comments?