Patellar tendinitis, left knee

This code identifies inflammation of the patellar tendon in the left knee, often referred to as "jumper's knee." It typically presents as pain and tenderness at the inferior pole of the patella, exacerbated by activities involving repetitive knee extension.

Apply this code when documentation specifies patellar tendinitis affecting the left knee. Supporting clinical notes should describe symptoms such as localized pain, tenderness, and functional limitations consistent with patellar tendon inflammation, and explicitly state the left side.

• Ensure laterality is clearly documented as "left" to avoid unspecified coding.
• Distinguish from patellofemoral pain syndrome (M22.2-) or other knee derangements.
• Consider an external cause code if the tendinitis is due to a specific injury or overuse from sports.