M23.41 identifies an intra-articular loose body — a free fragment of bone, cartilage, or both — specifically within the right knee joint.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 6
- Region
- Knee
Documentation tips
What should appear in the chart to support M23.41.
Source · Editorial brief grounded in 4 cited references ↓
- Confirm and record laterality explicitly as 'right knee' — vague documentation forces a downcode to M23.40 (unspecified).
- Include imaging findings that confirm intra-articular loose body: X-ray, MRI, or CT description of the fragment (size, location, ossified vs. purely cartilaginous).
- Document the suspected etiology (e.g., prior OA, osteochondral fracture, prior surgery) — this supports medical necessity and may require an additional code.
- If OA is a concurrent diagnosis, code it separately (e.g., M17.11 for right knee primary OA); M23.41 does not capture coexisting arthritis.
- Note any mechanical symptoms (locking, catching, giving way) in the clinical assessment — these directly support surgical necessity for arthroscopic loose body removal.
Related CPT procedures
Procedure codes commonly billed with M23.41. 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 M23.41 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Using M23.41 when osteochondritis dissecans (M93.2) is the documented underlying cause — M93.2 is the correct primary code in that scenario per the Excludes 1 note.
- Coding M23.41 for an acute traumatic osteochondral fracture at initial encounter — use an S-code (S80–S89 range) instead; M23.41 is for established, non-acute internal derangement.
- Failing to add a separate OA code when osteoarthritis is also documented — M23.41 does not capture coexisting degenerative joint disease.
- Defaulting to M23.40 (unspecified) when the operative report or imaging report clearly documents the right knee — specificity is required and auditable.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
Use M23.41 when documentation confirms the presence of one or more loose bodies (joint mice) within the right knee joint. Loose bodies form from fragmented articular cartilage, osteochondral chips, or ossified debris and commonly arise secondary to osteoarthritis, osteochondritis dissecans, prior trauma, or previous knee surgery. The diagnosis is typically confirmed by X-ray, MRI, or CT, and the imaging report should describe the intra-articular fragment(s).
M23.41 sits under parent code M23.4 (Loose body in knee). The laterality-specific siblings are M23.40 (unspecified knee) and M23.42 (left knee). Do not use M23.41 if the laterality is undocumented — drop to M23.40. If the loose body is a direct result of an acute injury being treated at this encounter, a current-injury S-code from S80–S89 takes priority over M23.41; the M23-range captures chronic or established internal derangement, not acute trauma.
Key Excludes 1 notes for the M23 category bar simultaneous use with ankylosis (M24.66), deformity of knee (M21.-), and osteochondritis dissecans (M93.2). If OCD is the documented etiology of the loose body, M93.2 is the correct code — not M23.41. When loose body coexists with documented knee osteoarthritis, code both conditions; M23.41 does not subsume the OA.
Sibling codes
Other billable codes under M23.4 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01What is the difference between M23.41 and M23.40?
02Can I use M23.41 if osteochondritis dissecans caused the loose body?
03Should I code M23.41 alongside an OA code if both are documented?
04Which CPT codes pair most commonly with M23.41?
05Is M23.41 appropriate for an acute traumatic knee injury encounter?
06Does M23.41 require a 7th-character extension?
07Can M23.41 be used if imaging shows the loose body but the knee has not yet been surgically confirmed?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 — https://www.cdc.gov/nchs/icd/icd-10-cm.htm
- 02icd10data.com 2026 ICD-10-CM Diagnosis Code M23.41 — https://www.icd10data.com/ICD10CM/Codes/M00-M99/M20-M25/M23-/M23.41
- 03AAPC Codify ICD-10-CM M23.41 — https://www.aapc.com/codes/icd-10-codes/M23.41
- 04CMS ICD-10-CM Guidelines — https://www.cms.gov/medicare/coding-billing/icd-10-codes
Mira AI Scribe
The Mira AI Scribe captures laterality ('right knee'), intra-articular fragment description from imaging (size, composition, number of bodies), mechanical symptoms (locking, catching), and any documented etiology such as OA or prior osteochondral injury. That captured detail prevents a downcode to M23.40 (unspecified) and provides the medical-necessity trail auditors expect for arthroscopic loose body removal claims.
See how Mira captures M23.41 documentation