M23.91 Unspecified internal derangement of right knee

Billable ICD-10-CM code, FY2026.

Applies from M23 Internal derangement of knee

Excludes1 (never code together)

• ankylosis (M24.66)
• deformity of knee (M21.-)
• osteochondritis dissecans (M93.2)

Excludes2 (not included here)

• current injury - see injury of knee and lower leg (S80-S89)
• recurrent dislocation or subluxation of joints (M24.4)
• recurrent dislocation or subluxation of patella (M22.0-M22.1)

MS-DRG index

Defines the logic of DRG(s) 562-563 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 717.9 Unspecified internal derangement of knee (approximate)

Code annotations containing back-references to M23.91

Back-references to M23

• Type 2 Excludes: M24.1 Other articular cartilage disorders ("internal derangement of knee (M23.-)")
• Type 2 Excludes: S83 Dislocation and sprain of joints and ligaments of knee ("internal derangement of knee (M23.-)")

Nearby codes

• M23.8X1 Other internal derangements of right knee
• M23.8X2 Other internal derangements of left knee
• M23.8X9 Other internal derangements of unspecified knee
• M23.9 Unspecified internal derangement of knee
• M23.90 Unspecified internal derangement of unspecified knee
• M23.91 Unspecified internal derangement of right knee (this code)
• M23.92 Unspecified internal derangement of left knee