Glossary · Clinical
ACL reconstruction
ACL reconstruction is a surgical procedure that replaces a torn anterior cruciate ligament with a graft—typically patellar tendon, hamstring tendon, or quadriceps tendon autograft, or allograft tissue—to restore knee stability. It is most commonly performed arthroscopically and reported with CPT 29888.
Verified May 8, 2026 · 8 sources ↓
Definition
Source · Editorial summary grounded in 8 cited references ↓
The anterior cruciate ligament (ACL) is the primary restraint against anterior tibial translation and rotational instability of the knee. When a complete tear renders the knee functionally unstable, reconstruction rather than simple repair is the standard of care for active patients. The surgeon drills tunnels through the tibia and femur, passes a graft through those tunnels to replicate the native ligament's orientation, and secures fixation—commonly with interference screws, cortical buttons, or staples—before closing. Graft choice (patellar tendon autograft, hamstring autograft, quadriceps tendon autograft, or allograft) affects both the operative note and the ICD-10 encounter coding, particularly if a prior graft has failed.
From a coding standpoint, the procedure is captured arthroscopically under CPT 29888 (arthroscopic ACL reconstruction, with or without meniscal repair) or, when performed open, under CPT 27407 or 27409 depending on concurrent ligament work. Concurrent procedures performed at the same encounter—such as partial meniscectomy (29881), chondroplasty, or loose-body removal—must be evaluated against NCCI PTP edits before appending modifier 59 or an X{EPSU} modifier. Fluoroscopy used intraoperatively to confirm tunnel placement is integral to the arthroscopic procedure and is not separately reportable per CMS NCCI Chapter IV policy.
ICD-10 diagnosis coding requires precision: an acute complete tear of the ACL (S83.511A for the right knee, initial encounter) is coded differently from a chronic or old tear (M23.619) or a failed prior reconstruction (T84.410A, mechanical complication of internal fixation device). Miscoding an acute tear as chronic—or failing to specify laterality—are leading causes of claim denial and payer-audit flags in orthopedic practices.
Why it matters
Selecting the wrong CPT code (e.g., billing open code 27407 for an arthroscopic case, or billing 29888 when a meniscal repair was bundled into the same code) triggers NCCI PTP edit denials and can escalate to post-payment audits. Separately, failing to distinguish an acute ACL tear from a chronic tear or a revision reconstruction in the ICD-10 diagnosis directly affects medical necessity review: payers routinely deny ACL reconstruction claims when the documented diagnosis reflects a chronic degenerative finding without supporting functional instability criteria, resulting in full claim write-offs that are difficult to overturn on appeal.
Common mistakes
Where people most often go wrong with this concept.
Source · Editorial brief grounded in cited references ↓
- Billing CPT 29888 and a separate diagnostic arthroscopy code (29870) for the same knee on the same day—diagnostic arthroscopy is integral when surgery proceeds.
- Appending modifier 59 to unbundle chondroplasty or synovectomy from 29888 when those services were performed in the same compartment during the same session, violating NCCI PTP policy.
- Using acute-injury ICD-10 code S83.511A (or contralateral equivalent) for a revision ACL reconstruction where the graft has previously failed—the correct code is T84.410A or M23.619.
- Omitting laterality modifiers (LT/RT) on the CPT claim line, which causes NCCI and payer-side claim suspensions.
- Reporting fluoroscopy guidance separately (e.g., 77002) when it was used only to confirm intraoperative tunnel positioning—CMS NCCI policy treats fluoroscopy as integral to arthroscopic procedures.
- Failing to document graft type, fixation method, and specific operative findings in the op note, leaving insufficient support for the billed CPT and ICD-10 codes during audit.
- Coding a primary ACL reconstruction with CPT 29888 when the surgeon performed a lateral extra-articular tenodesis concurrently—the additional procedure requires its own CPT code and supporting documentation.
- Applying the wrong encounter qualifier (initial 'A' vs. subsequent 'D' vs. sequela 'S') to the S83.5x1 code series when the patient has already begun active treatment.
Related codes
Codes commonly involved when this concept appears in practice.
CPT
- 29888 $889.47Arthroscopic-assisted anterior cruciate ligament repair or augmentation of the knee, performed endoscopically.
- 29889 $1,132.29Arthroscopic repair or augmentation of the posterior cruciate ligament (PCL) of the knee, performed under endoscopic visualization.
- 27407 $748.18Open primary repair of a cruciate ligament of the knee using direct suture or augmentation technique.
- 27409 $896.15Open primary repair of torn collateral ligament(s), cruciate ligament(s), and/or joint capsule of the knee — all structures addressed in a single operative session.
- 29881 $515.71Knee arthroscopy with surgical removal of the medial or lateral meniscus, including any associated cartilage shaving or debridement performed in the same or a separate compartment.
- 29880 $533.08Arthroscopic knee surgery removing both the medial and lateral menisci, including any meniscal shaving and chondroplasty of articular cartilage in any compartment when performed.
- 29876 $614.91Knee arthroscopy with major synovectomy involving two or more compartments for pathologic synovial disease
- 29870 $602.89Diagnostic arthroscopy of the knee, with or without synovial biopsy — a separate procedure designation meaning it bundles into any same-session surgical knee arthroscopy.
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 8 cited references ↓
01What is the correct CPT code for an arthroscopic ACL reconstruction?
02Can I bill a separate diagnostic arthroscopy code when the surgeon scoped the knee before proceeding to ACL reconstruction?
03Which ICD-10 code is correct for an acute complete ACL tear requiring reconstruction?
04Can a partial meniscectomy performed during the same ACL reconstruction session be billed separately?
05Is fluoroscopy separately billable during arthroscopic ACL reconstruction?
06How does graft type affect coding or reimbursement?
07What modifier is required when ACL reconstruction is performed as a return to the OR for a complication during the global period of a prior procedure?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01cms.govhttps://www.cms.gov/files/document/04-chapter4-ncci-medicare-policy-manual-2025finalcleanpdf.pdf
- 02cms.govhttps://www.cms.gov/files/document/2025nccimedicarepolicymanualcompletepdf.pdf
- 03icdcodes.aihttps://icdcodes.ai/diagnosis/anterior-cruciate-ligament-repair/
- 04aapc.comhttps://www.aapc.com/codes/coding-newsletters/my-orthopedic-coding-alert/orthopedic-coding-navigate-unbundling-and-ncci-guidelines-in-arthroscopic-surgery-180252-article
- 05aapc.comhttps://www.aapc.com/blog/35663-combat-common-denials-in-orthopedic-coding/
- 06coderoncall.nethttps://www.coderoncall.net/post/medicare-ncci-guidelines-for-arthroscopy
- 07AMA CPT Professional Edition – CPT codes 29888, 27407, 27409
- 08AAOS Coding and Reimbursement Resources – aaos.org
Mira AI Scribe
When Mira captures an ACL reconstruction encounter, it validates the following automatically: 1. LATERALITY: Confirms the operative note specifies left or right knee and maps LT or RT to every CPT line. If the surgeon documents bilateral procedures on the same date, Mira flags for 50 modifier review. 2. GRAFT TYPE: Extracts graft source (patellar tendon autograft, hamstring autograft, quadriceps autograft, or allograft) and surfaces it in the ICD-10 selection panel—particularly relevant if a prior graft is referenced, triggering T84.410A instead of the acute S83.5x1 series. 3. ACUTE vs. CHRONIC vs. REVISION: Scans the HPI and imaging section for language indicating prior reconstruction, prior graft, or chronic instability. Flags for coder review if acute-injury ICD-10 codes are pre-selected but chronic indicators are present in the record. 4. CONCURRENT PROCEDURE BUNDLING: When the op note documents concurrent meniscal work, chondroplasty, or loose-body removal, Mira runs a real-time NCCI PTP check against CPT 29888 and surfaces any edit conflicts before claim submission. It will prompt the coder to confirm whether a distinct compartment or distinct session justifies modifier 59/XS, or whether the service is integral and should be dropped. 5. FLUOROSCOPY EXCLUSION: Suppresses any auto-suggested fluoroscopy add-on code (e.g., 77002) when the primary code is an arthroscopic procedure, consistent with CMS NCCI Chapter IV policy. 6. DOCUMENTATION COMPLETENESS SCORE: Checks that the operative report includes graft type, tunnel creation technique, fixation method, and post-op plan before routing to billing—alerting the surgeon if required elements are missing.
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