ObjectivesTo determine the risk of lameness and the rate of subsequent medial patellar luxation surgery in dogs that present with occult Grade II medial patellar luxation.Materials and methodsRetrospective owner survey and review of clinical records of adult dogs diagnosed with Grade II medial patellar luxation that were initially asymptomatic and managed non‐surgically that had a minimum of 4‐year follow‐up. Clinical notes and owner questionnaires identified dogs that subsequently developed lameness and required surgery on the previously asymptomatic stifle.ResultsThirty‐eight dogs were included with an average follow‐up of 51 months. Seventeen dogs re‐presented for unscheduled contralateral medial patellar luxation surgery at an average of 15 months after initial presentation. A further two dogs had chronic contralateral limb lameness after an average of 33 months after initial surgery and may have been potential surgical candidates.Clinical SignificanceFifty percent of adult dogs presenting with occult Grade II medial patellar luxation subsequently developed chronic lameness or required surgery.