OBJECTIVE: To quantify the incidence, extent, and distribution of iatrogenic articular cartilage injury (IACI) during canine elbow arthroscopy and to investigate the effect of arthroscope size on IACI. STUDY DESIGN: Experimental study. SAMPLE POPULATION: A total of 72 elbows from fresh frozen large breed canine cadavers. METHODS: Elbows were alternately assigned to nine groups consisting of different combinations of arthroscope size (1.9, 2.4, 2.7 mm) and surgeon experience (novice, intermediate, advanced). Routine arthroscopic exploration of the elbow was performed. Number of obturator insertions and procedure time were recorded. Joints were disarticulated and stained with India ink. The incidence and total surface area of IACI were determined. A linear mixed model was used to evaluate the effect of arthroscope size on IACI, procedure time, and number of obturator insertions. RESULTS: The incidence of IACI was 100% with a median affected surface area of 10.6 mm CONCLUSION: Routine arthroscopic joint exploration resulted in IACI in 100% of elbows. The 2.4 mm arthroscope was associated with the lowest extent of IACI. CLINICAL SIGNIFICANCE: Surgeons should be aware that IACI occurs routinely during canine elbow arthroscopy. Further research is warranted to investigate clinical significance and to develop methods that minimize IACI during canine elbow arthroscopy.