The purpose of this study was to evaluate the long-term outcome of open patellar fractures and to compare their results with a matched group of patients with closed patellar injuries. Sixteen patients with open patellar fractures were followed up at a mean of 45 months (15–100). Functional outcome was evaluated using a visual analogue scale (VAS) and Knee and Osteoarthritis Outcome Score (KOOS). Sixteen patients with closed patellar fractures, matched for age, sex and fracture pattern, were randomly selected from our database to form the control group. Results and conclusion The most common mechanism of injury in the open patellar group was road traffic accidents (94%) whereas in the closed group it was falls (62%). A greater number of patients had associated injuries in the open patellar fracture group compared to the closed fracture group (13 versus 5, p = 0.01). The injury severity score (ISS) was significantly higher in the open patellar group (mean 22.75, range 5–50) compared with the closed group (mean 7.06, range 4–20); p < 0.0001. Patients with open patellar fractures also had a higher, though not statistically significant, incidence of complications, lower KOOS score and higher VAS for pain. Level of evidence Therapeutic study. Level III (Matched Cohort Study) [to evaluate the long-term outcome of open patellar fractures and to compare their results with a matched group of patients with closed patellar injuries].