M23.9
Unspecified internal derangement of knee
Not billable — category only FY2026 2025-10-01 → 2026-09-30
This is the unspecified option. 7 more
specific codes sit alongside it. Worth
checking whether the documentation supports one of them.
Exclusions 16 never code together
M23code
Excludes1
Excludes2
- current injury - see injury of knee and lower leg (S80-S89)S80-S89
- recurrent dislocation or subluxation of joints (M24.4)M24.4
- recurrent dislocation or subluxation of patella (M22.0-M22.1)M22.0-M22.1
M00-M99chapter
Excludes2
- arthropathic psoriasis (L40.5-)L40.5-
- certain conditions originating in the perinatal period (P04-P96)P04-P96
- certain infectious and parasitic diseases (A00-B99)A00-B99
- compartment syndrome (traumatic) (T79.A-)T79.A-
- complications of pregnancy, childbirth and the puerperium (O00-O9A)O00-O9A
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Q00-Q99
- endocrine, nutritional and metabolic diseases (E00-E88)E00-E88
- injury, poisoning and certain other consequences of external causes (S00-T88)S00-T88
- neoplasms (C00-D49)C00-D49
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)R00-R94
Excludes1 — never code together. The excluded condition and this one are mutually exclusive.
Excludes2 — not included here, but the patient may have both. Code both when documented.
Instructional notes 2
Index entries leading here 1
Alongside this code 7 same parent — M23
M23.0 Cystic meniscus category M23.2 Derangement of meniscus due to old tear or injury category M23.3 Other meniscus derangements category M23.4 Loose body in knee category M23.5 Chronic instability of knee category M23.6 Other spontaneous disruption of ligament(s) of knee category M23.8 Other internal derangements of knee category
Subordinate codes 3
Additional references
AHA Coding Clinic® Licence required
Official coding advice for this code. Published by the American Hospital Association. Not included in this installation.