Chronic instability of the left knee due to ligamentous laxity or insufficiency, representing a persistent, non-acute condition affecting joint integrity on the left side.
Verified May 8, 2026 · 5 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 10
- Region
- Knee
Documentation tips
What should appear in the chart to support M23.52.
Source · Editorial brief grounded in 5 cited references ↓
- Explicitly document 'left knee' and 'chronic instability' — laterality and chronicity are both required to justify M23.52 over unspecified alternatives.
- Record the specific ligament(s) involved (ACL, PCL, MCL, LCL) and the mechanism or history of original injury, including whether prior acute treatment was attempted.
- Include objective instability test results by name (e.g., Lachman test grade, anterior drawer, pivot shift, varus/valgus stress) with a grade or qualitative descriptor (trace, 1+, 2+, 3+).
- Document MRI or stress radiograph findings that corroborate instability — ligament signal changes, laxity on stress views, or joint translation measurements.
- Note functional impact: frequency of giving-way episodes, activity limitations, and any bracing or physical therapy already completed, to support medical necessity for surgical intervention.
Related CPT procedures
Procedure codes commonly billed with M23.52. 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 M23.52 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Assigning M23.52 for an acute ligament tear — acute injuries belong in the S83.– sprain/tear codes with a 7th-character 'A' for initial encounter, not M23.52.
- Using M23.52 alone for bilateral chronic instability — ICD-10-CM has no single bilateral code at M23.5x; you must also assign M23.51 for the right knee when both sides are documented.
- Dropping to the unspecified parent M23.50 when the note clearly states 'left knee' — specificity is documented and the more specific code is required.
- Confusing chronic instability (M23.52) with chronic ligament pain without instability — M23.52 requires documented functional instability, not just residual pain from an old injury.
- Omitting M23.52 as a secondary code when the encounter is primarily for ACL reconstruction — instability is often the medical necessity diagnosis that justifies the procedure and must appear on the claim.
Clinical context
Source · Editorial summary grounded in 5 cited references ↓
M23.52 applies when the left knee demonstrates chronic — not acute — instability. This includes old, unresolved ligamentous disruptions such as chronic ACL, PCL, MCL, or LCL insufficiency where the injury has moved beyond the acute phase and stability has never been restored. The code captures the functional consequence (instability) rather than the specific ligament involved; if payer policy or clinical documentation requires ligament specificity, note the affected structure in the record even though the ICD-10-CM code itself doesn't differentiate.
Use M23.52 in pre-operative workups for ligament reconstruction, during conservative management (bracing, physical therapy), or when instability is the primary diagnosis driving an office visit or imaging order. It pairs logically with functional instability complaints: giving-way episodes, positive Lachman, anterior/posterior drawer, or varus/valgus stress testing documented in the note.
Do not use M23.52 for an acute ligament tear — those belong in the S83.– range (sprains/tears of ligaments of the knee) with the appropriate 7th-character extension. M23.52 is reserved for the chronic, established condition. If both knees are affected, M23.52 covers the left side; add M23.51 for the right. There is no bilateral-specific code at the M23.5 level in ICD-10-CM — bilateral presentations require two codes.
Sibling codes
Other billable codes under M23.5 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 5 cited references ↓
01What is the difference between M23.52 and an S83.– ligament tear code?
02Can I use M23.52 for bilateral chronic knee instability?
03Does M23.52 require a specific ligament to be named in the diagnosis?
04Which CPT procedures most commonly pair with M23.52?
05Is M23.52 valid for a pre-operative diagnosis on a surgical claim?
06What documentation is needed to avoid a medical necessity denial when billing M23.52?
07Should M23.52 be used after a successful ACL reconstruction with no residual instability?
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/M23-/M23.52
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M23.52
- 04cms.govhttps://www.cms.gov/medicare/coding-billing/icd-10-codes
- 05cdc.govhttps://www.cdc.gov/nchs/icd/icd-10-cm/index.html
Mira AI Scribe
Mira AI Scribe captures the laterality ('left'), chronicity (no acute event at this visit, history of prior ligament injury), objective instability test findings (Lachman, drawer, pivot shift with grade), MRI or imaging interpretation, and prior conservative care — bracing and PT history. This prevents a downcode to M23.50 (unspecified) and closes the documentation gap that triggers medical necessity denials for ligament reconstruction procedures.
See how Mira captures M23.52 documentation