Purpose: To assess and quantify the association of haemophilic arthropathy, measured by the radiological Pettersson score, with the number of joint bleeds suffered by the patient. Material and Methods: In order to quantify the effect of the cumulative number of joint bleeds on the Pettersson score, a study was performed using 295 Pettersson scores obtained in 117 patients with severe haemophilia. The patients were born between 1965 and 1994, and had no history of inhibitors. The number of joint bleeds was determined annually from the entry in the clinic and onwards. The localization of bleeds was not assessed. The patients entered the clinic at a median age of 3.6 years, and received intermediate dose prophylaxis, starting at a median age of 5.3 years. Evaluation of 1643 treatment years showed a mean of 6.8 joint bleeds/year. Pettersson scores were obtained at a mean age of 15.9 years (range 1.7–32.9) and had a median value of 4 points (range 0–50). Results and Conclusion: The Pettersson scores began to rise after the age of 5 years and increased with one point for every 13 joint bleeds (95% confidence interval 11–15). No evidence was found of ‘autonomous’ progression of Pettersson scores, independent of bleeds.