In a previous article titled ICD-10: The Axis of Classification, we had indicated that one method for preparing your key stakeholders for the transition to ICD-10 was to break ICD-10-CM down into its basic components: chapters and axes of classification. This article will continue that theme in reviewing changes we will encounter in ICD-10-CM’s Chapter 13, “Diseases of the Musculoskeletal System & Connective Tissue.”

In the Fiscal Year (FY) 2012 version of ICD-9-CM, the code range for Chapter 13 is 710-739 and consists of 892 codes. Compare this to the FY2012 version of ICD-10-CM, where Chapter 13’s code range is M00-M99 and consists of 6,339 codes. This comparison nets us an increase of 5,447 additional codes, or 611 percent.

The ICD-10-CM version of Chapter 13 contains nine percent of the total volume of codes available, and ranks third in terms of having the greatest number of total codes. After having identified the volume of codes within this chapter, you likely are wondering, why the significant increase? The answer to that can be found by reviewing the general changes that have occurred in this chapter. We start with noting that there are 18 subchapters used to report the type of disease of the musculoskeletal system or connective tissue.

Chapter 13 Chapter Blocks

M00-M02 Infectious arthropathies
M05-M14 Inflammatory polyarthropathies
M15-M16 Osteoarthritis
M20-M25 Other joint disorders
M26-M27 Dentofacial anomalies [including malocclusion] and other disorders of jaw
M30-M36 Systemic connective tissue disorders
M40-M43 Deforming dorsopathies
M45-M49 Spondylopathies
M50-M54 Other dorsopathies
M60-M63 Disorders of muscles
M65-M67 Disorders of synovium and tendon
M70-M79 Other soft tissue disorders
M80-M85 Disorders of bone density and structure
M86-M90 Other osteopathies
M91-M94 Chondropathies
M95 Other disorders of the musculoskeletal system and connective tissue
M96 Intraoperative and postprocedural complications and disorders of musculoskeletal system, not elsewhere classified
M99 Biomechanical lesions, not elsewhere classified



In general, the changes you will note when reviewing Chapter 13 are:

  • There are four times as many subchapters as in this chapter in ICD-9-CM. There are also many new categories and codes.
  • Many codes have been relocated from other chapters in ICD-9-CM to Chapter 13 in ICD-10-CM. (e.g., gout, osteomalacia, malocclusion, dislocation of the knee, etc.)
  • There is an expanded use of instructional notes that instruct us to assign, and sequence first, codes to capture any associated or underlying conditions.
  • Be sure to brush up on your anatomy, as this chapter provides many opportunities to capture greater specificity of the anatomical site.
  • Some conditions allow the reporting of multiple sites with one code. When no “multiple site” code is available, yet more than one bone, muscle, or joint is involved, assign separate codes for each site.
  • Laterality is required for many codes in this chapter.
  • 7th character extensions are used to report episode of care for many conditions in Chapter 13:
    • A initial encounter for fracture
    • B subsequent encounter for fracture with routine healing
    • G subsequent encounter for fracture with delayed healing
    • K subsequent encounter for fracture with nonunion
    • P subsequent encounter for fracture with malunion
    • S sequelae
  • Musculoskeletal conditions require documentation of acute trauma vs. chronic or recurrent conditions. Musculoskeletal conditions that are healed, chronic, or recurrent are classified to Chapter 13; however, current, acute bone, muscle, or joint injuries are classified to Chapter 19, “Injury, Poisoning and Certain Other Consequences of External Causes.”

In exploring Chapter 13 in greater detail, you will note the following:

  • Traumatic fractures are classified to Chapter 19, “Injury, Poisoning and Certain Other Consequences of External Causes,” in ICD-10-CM.
  • Pathological fractures are now classified by etiology/type, site, laterality, and episode of care.
  • ICD-10-CM offers combination codes to report type of osteoporosis with or without current pathological fracture. The site captures the site of the fracture, not the site of osteoporosis.
  • The term “fragility fracture” is included in ICD-10-CM and is defined as a “fracture sustained with trauma no more than a fall from a standing height or less that occurs under circumstances that would not cause a fracture in a normal healthy bone.”
  • Pyogenic arthritis is now classified by organism, specific site, and laterality.
  • Rheumatoid arthritis has 191 code options by type, manifestation, and laterality.
  • Osteomyelitis is now classified by type, acuity, specific site, and laterality.
  • Osteoarthritis is now classified by type, specific site, and laterality.
  • Systemic Lupus Erythematosus (SLE) is now classified by etiology or manifestation.
  • Scoliosis is classified by type and anatomical region of spine.
  • Pain in the limb, which had only one code option in ICD-9-CM, now has 31 code options based on specific site and laterality.
  • There are new codes for intraoperative and postprocedural complications and disorders of the musculoskeletal system which can be further classified by type of complication, the condition caused by device, laterality, hemorrhage, hematoma, accidental puncture, etc.

These are just some of the examples of changes one can anticipate when reporting diseases of the musculoskeletal system and connective tissue using ICD-10-CM.

About the Author

Angela Carmichael, MBA, RHIA, CCS, CCS-P, is director of HIM compliance for J.A. Thomas & Associates. Angela earned a Bachelor of Science degree, in Health Services Administration from Barry University and a MBA from Nova Southeastern University. She is a Registered Health Information Administrator and also has achieved the designations of Certified Coding Specialist, and Certified Coding Specialist-Physician and AHIMA Approved ICD-10-CM/PCS Instructor.

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