M24.20 captures a ligament disorder — including instability from old ligament injury or ligamentous laxity NOS — when no anatomical site is documented in the record.
Verified May 8, 2026 · 6 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 10
- Region
- General
Documentation tips
What should appear in the chart to support M24.20.
Source · Editorial brief grounded in 6 cited references ↓
- Document the specific joint and laterality (e.g., 'right ankle ligamentous laxity') so you can move to a site-specific M24.2xx code and avoid M24.20 entirely.
- Distinguish chronic/old ligament injury (M24.2x) from an acute ligament tear (S-code) — the encounter type drives which chapter applies.
- If the note describes knee ligament instability, do not use M24.20; code from M23.5–M23.8X9 per the Type 1 Excludes instruction under M24.2.
- For workers' compensation or personal injury claims, pair M24.20 with an external cause code documenting mechanism — payers may deny without it.
- When M24.20 appears on a surgical claim, auditors will flag the mismatch between a site-specific procedure code and a site-unspecified diagnosis; query the operative note for the correct joint before billing.
Related CPT procedures
Procedure codes commonly billed with M24.20. Linking the right diagnosis to the right procedure is what establishes medical necessity.
Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis
Common coding pitfalls
The recurring mistakes coders make with M24.20 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Using M24.20 on a surgical claim when the operative report clearly names the affected joint and side — always drill down to the six-character site-specific code for procedural claims.
- Applying M24.20 to knee ligament instability, which is a Type 1 Excludes violation; knee ligament disorders belong in M23.5–M23.8X9.
- Coding M24.20 for an acute ligament tear seen at the initial injury encounter — acute injuries require an S-code (injury chapter) with the appropriate 7th character, not an M-code.
- Leaving M24.20 on a claim supporting a ligament injection (CPT 20550/20551) when the CMS LCD for injections lists only site-specific M24.2xx codes as supporting medical necessity — the unspecified code may not satisfy LCD requirements.
Clinical context
Source · Editorial summary grounded in 6 cited references ↓
M24.20 sits at the bottom of the M24.2 hierarchy and is the fallback only when the treating provider has not documented which joint or anatomical site is affected. The parent category M24.2 covers ligament disorders broadly — chronic instability secondary to old ligament injury and ligamentous laxity NOS — but M24.2 itself is non-billable. M24.20 is the billable code when site is genuinely unspecified.
In orthopedic practice, M24.20 should be rare. The M24.2x subcodes cover shoulder (M24.21x), elbow (M24.22x), wrist (M24.23x), hand (M24.24x), hip (M24.25x), ankle (M24.27x), and foot (M24.27x) — all with laterality. If the provider has documented the joint and side, use the site-specific six-character code instead. M24.20 is appropriate only when documentation genuinely fails to identify an anatomical location, such as a referral note that names no joint.
Note the Type 1 Excludes under M24.2: internal derangement of the knee (M23.5–M23.8X9) is excluded entirely from this category. Do not use M24.20 for knee ligament instability — those cases belong in M23. Current injuries are also excluded from M24; acute ligament tears code from the S-code injury chapter, not M24.20.
Sibling codes
Other billable codes under M24.2 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 6 cited references ↓
01When is M24.20 actually the correct code to use?
02Can I use M24.20 for a knee ligament problem?
03Can M24.20 support a ligament injection claim?
04Should I use M24.20 or an S-code for a patient with a ligament tear seen on the day of injury?
05Is M24.20 billable on its own, or do I need to use the parent M24.2?
06What MS-DRG does M24.20 map to?
07Does M24.20 require a 7th character extension?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (effective Oct 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M20-M25/M24-/M24.20
- 03icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M20-M25/M24-/M24.2
- 04cms.govhttps://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=57079&ver=7&
- 05cms.govhttps://www.cms.gov/files/document/fy-2024-icd-10-cm-coding-guidelines-updated-02/01/2024.pdf
- 06aapc.comhttps://www.aapc.com/codes/icd-10-codes/M24.20
Mira AI Scribe
Mira captures the affected joint name, laterality, and whether the ligament condition is chronic/old versus acute, along with any imaging or stress-test findings that confirm laxity or instability. That documentation drives the coder to a site-specific M24.2xx code instead of M24.20, preventing LCD-based denials on injection or surgical claims and eliminating the audit flag that follows an unspecified site code on a procedure-specific bill.
See how Mira captures M24.20 documentation