M23.9Unspecified internal derangement of knee

M23.9 is the ICD-10-CM diagnosis code for unspecified internal derangement of knee. It belongs to category M23 (internal derangement of knee), block M20-M25 (other joint disorders) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.

Within M23, choose M23.9 (Unspecified internal derangement of knee) only when documentation doesn't support a more specific option: cystic meniscus (M23.0), derangement of meniscus due to old tear or injury (M23.2), other meniscus derangements (M23.3), Loose body in knee (M23.4), chronic instability of knee (M23.5), other spontaneous disruption of ligament(s) of knee (M23.6) and other internal derangements of knee (M23.8).

To report this condition, pick the subcode that matches the documentation: M23.90 (knee), M23.91 (knee) and M23.92 (knee).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.