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ICD-10 Guide
DiagnosesArthritis Left Knee

Arthritis Left Knee

ICD-10 Coding for Arthritis of the Left Knee(M17.12, M17.32)

PRIMARY SPECIALTYOrthopedics
COMPLEXITYHigh
LAST UPDATED09/15/2025
Sam Tuffun, PT, DPT
Physical Therapist | Medical Coding & Billing Contributor

Diagnosis Overview

What is Arthritis Left Knee?
Essential facts and insights about Arthritis of the Left Knee

Key Clinical Considerations:

  • Presence of joint pain, swelling, and stiffness in the left knee.
  • Laboratory findings may include elevated inflammatory markers such as ESR or CRP.
  • Physical examination may reveal tenderness, decreased range of motion, and crepitus in the left knee.
  • Imaging findings may include joint space narrowing, osteophyte formation, or subchondral sclerosis on X-ray.
  • Severity criteria may include the degree of functional impairment and pain levels assessed using validated scales.

Clinical Information

Clinical Criteria & Documentation Requirements

  • Medical records must document the patient's history, including onset and duration of symptoms.
  • Specific terminology such as 'osteoarthritis' or 'rheumatoid arthritis' must be clearly stated.
  • Examples include documenting the patient's pain level, physical exam findings, and imaging results.
  • Medical necessity must be established through documentation of the impact on daily activities.
  • Quality measures may require documentation of pain assessments and functional status evaluations.

Coding Guidelines

Usage Guidelines & Examples

  • Use M17.12 for unilateral osteoarthritis of the left knee when the condition is confirmed.
  • Do not use this code for conditions like post-traumatic arthritis or other knee disorders not specified as osteoarthritis.
  • M17.0 (Bilateral primary osteoarthritis of the knee) is similar but indicates bilateral involvement.
  • Common errors include using the wrong laterality or failing to document the type of arthritis.
  • In complex cases, ensure to differentiate between primary and secondary arthritis for accurate coding.

Code Exclusions

Important Exclusions

  • Excludes conditions such as rheumatoid arthritis (M05) and septic arthritis (M00-M03).
  • Alternative codes for excluded conditions include M05 for rheumatoid arthritis affecting the knee.
  • Conditions are excluded due to differing pathophysiology and treatment approaches.
  • Common mistakes include misclassifying rheumatoid arthritis as osteoarthritis.
  • Related but distinct conditions include bursitis and tendinitis of the knee.

Related ICD-10 Codes

Primary Codes
M17.12
Unilateral primary osteoarthritis of the left knee
M17.32
Unilateral post-traumatic osteoarthritis of the left knee
Ancillary Codes
M25.562
Z68.35
Differential Codes
M17.32
M06.9
M17.12

Related CPT Codes

CPT codes will be available in a future update.

Specialty Focus

Primary Specialty

Orthopedics

Specialty Applications

  • Applies to patients with diagnosed osteoarthritis or post-traumatic arthritis of the left knee.
  • Common in older adults, particularly those with a history of joint injuries or obesity.
  • Clinical settings include outpatient orthopedic clinics and rehabilitation facilities.
  • Specialty-specific applications are relevant in orthopedics and rheumatology.
  • Used in treatment contexts involving physical therapy, medication management, and surgical interventions.

Coding Complexity

High Complexity

This diagnosis requires careful attention to:

  • Comprehensive clinical documentation
  • Accurate code selection based on clinical criteria
  • Proper exclusion considerations
  • Specialty-specific coding guidelines

Documentation

Documentation Templates

Template 1

Template: 'Patient diagnosed with left knee osteoarthritis based on clinical findings of pain and swelling.'

Template 2

Template: 'Clinical presentation consistent with unilateral osteoarthritis including stiffness and decreased range of motion.'

Template 3

Template: 'Diagnostic criteria for osteoarthritis met as evidenced by X-ray findings of joint space narrowing.'

Template 4

Template: 'Treatment plan initiated for left knee arthritis with physical therapy and NSAIDs.'

Template 5

Template: 'Follow-up care for left knee osteoarthritis including monitoring of pain levels and mobility.'

Billing Information

Billing Considerations

  • Ensure proper documentation for billing
  • Verify code specificity requirements
  • Check for any additional codes needed
  • Review payer-specific guidelines

Common Issues

  • Insufficient clinical documentation
  • Incorrect code selection
  • Missing supporting diagnoses
  • Timing and frequency documentation

Frequently Asked Questions

What documentation is required for this diagnosis?

Documentation must include patient history, physical exam findings, and imaging results.

How does this differ from similar diagnoses?

Differentiation is based on the type of arthritis and associated symptoms.

What are common billing considerations?

Ensure accurate coding to reflect the specific type of arthritis for optimal reimbursement.

What procedures are typically associated?

CPT codes for knee injections, physical therapy, and arthroscopy may be relevant.

Are there any quality reporting implications?

Quality measures may include tracking pain levels and functional outcomes in patients.