S39.012A: Strain of muscle, fascia and tendon of lower back, initial encounter
Region: Lumbar injury
By Dr. Daniel Turner, DC · Reviewed September 2, 2026
What does S39.012A mean?
S39.012A is the ICD-10-CM code for a strain of the muscles, fascia, or tendons of the lower back at the initial encounter, the injury code for the pulled low back.
Searched as lumbar strain ICD 10, pulled lower back muscle code, and low back strain diagnosis code for work injuries.
When does a chiropractor use S39.012A?
Covers the acute muscular low back injury: the lifting incident, the sudden load, the collision bracing pattern. Alongside the ligament sprain S33.5XXA it documents the full soft tissue injury and supports the massage and manual therapy service lines in the treatment plan. For work injuries it is frequently the primary code the workers compensation payer expects.
Coding rules that matter
- ✓Seven characters required with the standard A, D, S sequence
- ✓Non traumatic muscle spasm is M62.830; this code asserts an injury event
- ✓Document the mechanism in the intake; strain without a described event invites downcoding
The codes around S39.012A
| Code | Description |
|---|---|
| S39.012A | Low back strain, initial encounter (this code) |
| S39.012D | Low back strain, subsequent encounter |
| S39.012S | Low back strain, sequela |
| S33.5XXA | Lumbar ligament sprain, initial encounter |
| M62.830 | Muscle spasm of back, non traumatic |
When S39.012A is the wrong code
Not for chronic myofascial low back pain with no event, which belongs on M62.830 or the M54.5 family. The injury code needs its injury: a mechanism documented at intake. Workers compensation payers in particular expect the strain code with the event, not the pain code without it.
How does S39.012A work on Medicare chiropractic claims?
Secondary behind M99.03 when Medicare is the payer; in workers compensation and PI contexts it is often carried as a lead code per the payer’s own conventions.
Where claims go wrong
Using it for chronic myofascial complaints with no event; seventh character neglect; failing to record the mechanism that justifies the injury code.
How Cervica helps with S39.012A
Cervica validates diagnosis pointers line by line before a claim goes out, checks the Medicare subluxation pairing and region agreement automatically, and carries diagnoses forward from the SOAP note so the claim always matches what the documentation actually says.
Related codes
Quick answers
What does S39.012A mean?
S39.012A is the ICD-10-CM code for a strain of the muscles, fascia, or tendons of the lower back at the initial encounter, the injury code for the pulled low back.
When does a chiropractor use S39.012A?
Covers the acute muscular low back injury: the lifting incident, the sudden load, the collision bracing pattern. Alongside the ligament sprain S33.5XXA it documents the full soft tissue injury and supports the massage and manual therapy service lines in the treatment plan. For work injuries it is frequently the primary code the workers compensation payer expects.
How does S39.012A work on Medicare chiropractic claims?
Secondary behind M99.03 when Medicare is the payer; in workers compensation and PI contexts it is often carried as a lead code per the payer’s own conventions.
General information for billing teams, not medical, legal, or coding advice for any individual claim. ICD-10-CM is maintained by CMS and the National Center for Health Statistics; the official code set and guidelines control. Payer policies vary.