Question: The practitioner documents that a patient had a charley-horse. Which code is the most accurate choice? New Hampshire Subscriber Answer: Most likely you’ll turn to M62.831 (Muscle spasm of calf). Here’s why. As you’ve probably already noticed, when you look the condition up in the ICD-10-CM index, you see two different codes. M62.831 is listed first, and in the corresponding tabular entry, “Charley-horse” is listed as a synonym under M62.831. The other entry in the index under “Charley-horse” is S76.11- (Strain of quadriceps muscle, fascia and tendon). This is an injury code, which is further reflected in the use of “traumatic” before the code in the index entry. So, unless the doctor has indicated that the condition was caused by an injury, you can rule out S76.11-. You’re now left with the musculoskeletal code, which is M62.831.