M23.5Chronic instability of knee

M23.5 is the ICD-10-CM diagnosis code for chronic instability 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 (internal derangement of knee), M23.5 is specifically for chronic instability of knee. Related codes cover 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), other spontaneous disruption of ligament(s) of knee (M23.6), other internal derangements of knee (M23.8) and unspecified internal derangement of knee (M23.9).

To report this condition, pick the subcode that matches the documentation: M23.50 (unspecified knee), M23.51 (right knee) and M23.52 (left knee).

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