ICD-10 Code S83.512D: Left knee ACL sprain, subsequent encounter

Key takeaways

ICD-10 Code S83.512D describes a sprain of the anterior cruciate ligament of the left knee at a subsequent encounter.

The 7th character D applies during follow-up, rehabilitation, and routine monitoring, once definitive treatment for the injury has ended.

Confusing S83.512D with S83.512A is one of the most common coding errors on ACL claims, and it often triggers denials.

Practice management software like Pabau links visit type to encounter suffix, so ACL claims carry the correct 7th character.

ICD-10 Code S83.512D is a billable diagnosis code for a sprain of the anterior cruciate ligament of the left knee at a subsequent encounter. It applies once active treatment has ended and the patient is in follow-up or rehabilitation for the same injury.

The suffix is where ACL claims go wrong, because coders often read subsequent as the patient’s second visit. This reference covers the official descriptor, billable status, suffix selection, the related S83.5 codes, the CPT crosswalk, and documentation requirements.

S83.512D is confirmed billable in the CDC/NCHS ICD-10-CM official tool and the 2026 tabular list. The single code string carries laterality, the anatomical structure, the injury type, and the encounter phase. That combination satisfies payer specificity requirements on its own.

Understanding the 7th character D: Subsequent encounter explained

The 7th character is where most ACL coding errors start. ICD-10-CM appends it to traumatic injury codes to show which phase of care the encounter represents. Payers and auditors read that character as a clinical statement about the visit.

The CMS ICD-10-CM coding guidelines are specific on one point. Subsequent encounter does not mean the patient’s second visit. It means that active treatment has finished. A patient in week six of post-surgical ACL rehabilitation takes D on every visit that week.

Treatment phase decides the suffix, not visit count. While a clinician is still providing active treatment, A applies. That covers surgical recovery, bracing management, and the initial immobilization period.

Once the patient moves into monitored recovery or rehabilitation, D takes over. The diagram below marks where that switch falls in a single ACL episode.

S83.512A vs S83.512D vs S83.512S: Choosing the right encounter suffix

All three codes share the same anatomical base, a sprain of the anterior cruciate ligament of the left knee. The suffix is the only variable, and it changes what the claim says about the visit.

Sequela coding needs a second code for the sequela condition itself. If the documented late effect is chronic knee instability, the instability code accompanies S83.512S on the claim. The original injury code alone will not support a sequela claim.

Related ICD-10-CM codes in the S83.5 family

S83.512D sits inside the S83.5 cruciate ligament sprain subcategory. Coders handling ACL injuries on both knees, or with undocumented laterality, need the full code family. Payers increasingly flag claims where the billed side does not match the operative or diagnostic report.

Use the unspecified laterality codes (S83.519x) only when the record genuinely does not document which knee is affected. In practice, any legible clinical note, imaging report, or operative record names the side. Billing S83.519D when the left knee is documented is a specificity failure under the ICD-10-CM Official Guidelines.

Where the code sits in the ICD-10-CM hierarchy

The parent chain helps coders navigate the tabular list during an audit. It also confirms that exclusion notes higher up the tree do not affect S83.512D. The full hierarchy, per the WHO ICD-10 classification structure, runs like this:

• Chapter 19: Injury, poisoning and certain other consequences of external causes (S00-T88)
• Block S80-S89: Injuries to the knee and lower leg
• Category S83: Dislocation and sprain of joints and ligaments of knee
• Subcategory S83.5: Sprain of cruciate ligament of knee
• S83.51: Sprain of anterior cruciate ligament of knee
• S83.512: Sprain of anterior cruciate ligament of left knee
• S83.512D: Sprain of anterior cruciate ligament of left knee, subsequent encounter

No Type 1 Excludes note at the S83.5 level stops S83.512D from being billed alongside standard physical therapy evaluation or management codes. Check the S83 parent notes for Type 2 Excludes notes, which may call for an additional code such as an open wound code.

Documentation requirements for S83.512D

Thin documentation is the most common reason an S83.512D claim gets denied. The encounter note has to support every element the code carries. Payers run automated edits that flag ACL sprain claims where the documented visit type contradicts the suffix.

The clinical record needs these elements to substantiate S83.512D:

• Laterality confirmed: The note identifies the left knee as the affected joint. Left knee ACL sprain in the assessment or clinical impression satisfies this.
• Injury type documented: The note describes a sprain, meaning a ligament stretch or a partial or complete tear, rather than a fracture or dislocation.
• Treatment phase established: The record shows that definitive treatment is finished. Phrases such as rehabilitation phase, follow-up for ACL sprain, or physical therapy for left knee ACL injury establish the subsequent encounter.
• Continuity of care: The record links this visit to the original ACL injury. Prior visit notes or a treatment summary confirming initial active treatment help during an audit.
• Provider credentials: The treating provider is licensed and credentialed to document and bill the services rendered at this encounter.

Structured intake forms capture laterality, injury mechanism, and treatment phase at the point of care. That puts the details a coder needs on file before the chart reaches billing.

CPT codes commonly used with S83.512D

S83.512D is a diagnosis code, so every claim pairs it with a CPT procedure code. The CPT code says what was done at the visit and S83.512D says why. 97110 is the code most often billed alongside it on physical therapy claims.

Payer bundling rules apply when several physical therapy codes are billed for the same session. Check the payer’s own policy before you submit a multi-code PT claim. Edit checking at the point of submission catches most bundling conflicts, which is the top denial type on ACL rehabilitation claims.

Common coding errors and how to avoid them

S83.512D denials cluster around four predictable mistakes. They show up on remittance advice from major payers, and a clear workflow prevents each one.

Encounter-suffix mismatches come back with specific denial codes, so tracking which ones recur tells you where the workflow breaks. Catching the pattern before submission beats correcting it after the denial arrives.

• Error 1: using S83.512A when active treatment is over. This is the most frequent mistake. Coders default to A because the injury started there. Once rehabilitation begins, every encounter takes D, and applying A on a PT visit triggers a payer edit.
• Error 2: using unspecified laterality (S83.519D) when the note documents the left knee. Specificity errors generate claim edits and payer queries. If the note says left knee ACL sprain, bill S83.512D. This is one of the most flagged failures in orthopedic billing audits.
• Error 3: hunting for a separate ACL tear code. There is none. The ICD-10-CM index routes tear of the anterior cruciate ligament to S83.51x, so the sprain codes cover partial and complete tears. S83.512D applies to a left ACL sprain, strain, or tear at a subsequent encounter.
• Error 4: skipping the sequela companion code. When the S suffix is right, the late effect needs its own code. Billing S83.512S without a code for the sequela condition, such as chronic instability, fails claim editing.

How practice management software prevents S83.512D coding errors

The errors above share one cause. The encounter suffix gets picked manually at coding time, with no decision point recorded in the clinical workflow. The claim then rests on how a coder reads unstructured text in the note.

Practice management software like Pabau ties the visit type to the encounter suffix. The trigger then sits in the clinical record instead of a coder’s judgment.

Structured visit templates hold laterality and treatment phase as fields, so the billing team reads them in one place. Claims built from those templates run through error-checking claims management software before they reach the payer.

Pabau integrates with Claim.MD, a US clearinghouse supporting electronic submission to thousands of US payers. Claims carrying S83.512D pass through edit checking, eligibility verification, and electronic remittance advice processing before submission. Sports medicine and physical therapy practices run that alongside their clinical notes, instead of in separate billing software.

Reduce ACL claim denials with smarter billing workflows

Pabau’s claims management software helps orthopedic and physical therapy practices submit accurate ICD-10 and CPT pairings. Built-in edit checking, eligibility verification, and Claim.MD submission catch errors before the payer does.

Book a demo

Conclusion

S83.512D is not hard to code once the suffix logic is clear. The harder part is making sure the person coding knows which phase of care the visit belongs to.

More coder training helps less than a change to the workflow. Write the treatment phase into the visit record on the day it changes, and the suffix follows on its own.

Practices that do this stop reworking ACL claims and start clearing them on the first pass. Book a demo to see how Pabau handles coding, documentation, and claim submission for musculoskeletal practices.

Continue your research

Want to know how clearinghouse submission cuts ACL denials? Claim.MD clearinghouse explains how electronic claim submission works and where denial prevention starts.

Aiming to get ACL claims paid on the first pass? Clean claim submission shows what a payer needs before the claim leaves your practice.

Denials already piling up on rehab claims? Denial management in healthcare covers how to work a denial queue and stop the repeat causes.

Need a billing compliance framework that covers every claim type? Medical billing compliance sets out the documentation, coding, and submission standards to work to.

Frequently asked questions