Unilateral primary osteoarthritis, left knee

This code signifies the presence of degenerative joint disease, specifically primary osteoarthritis, affecting only the left knee. It indicates that the cartilage in the left knee joint has deteriorated due to age-related wear and tear, without an identifiable underlying cause like trauma or inflammation.

Apply this code when documentation clearly states a diagnosis of primary osteoarthritis localized to the left knee. This is appropriate for patients presenting with left knee pain, stiffness, and imaging findings (e.g., X-ray) consistent with osteoarthritis, where no secondary cause is identified.

• Ensure documentation specifies "primary" osteoarthritis and laterality (left knee).
• Do not use if the osteoarthritis is secondary to trauma, infection, or another systemic condition; a more specific code for secondary osteoarthritis would be required.
• If both knees are affected, a bilateral code (M17.10) or separate codes for each knee (M17.11 and M17.12) may be appropriate depending on documentation.