The minimum goal of secondary prophylaxis may be to delay the progression of haemarthropathy below a critical level over which it has a great impact on the QoL of haemophilia patients. However, the critical level of haemarthropathy may be different across countries. For these reasons, the impact of haemarthropathy on the QoL in Korean haemophilia A patients was investigated. Depending on observed Pettersson scores of 27 severe haemophilia A patients, they were divided into three groups, P (Pettersson score) ≤10, P11~19 and P ≥ 20 groups. The QoL of each patient, assessed by the SF36, was compared between the groups. In addition, the changes in the QoL of the patients were observed according to the changes of Pettersson scores to find out the critical level of arthropathy. None of the scores of the SF36 scales were different between the P ≤ 10 and P11~19 groups. In contrast, the scores of PF and MH scales were significantly different between the P11~19 and P ≥ 20 groups. When changes in the scores of each scale in the SF36 were observed according to changes in Pettersson scores, the average P score of 13.0 ± 2.7 was thought to be the critical level of haemarthropathy because above that level, haemarthropathy and physical and mental health of the patients rapidly deteriorated. The progression of haemarthropathy to the critical level should be delayed as long as possible to prevent or to delay a rapid deterioration of the QoL of Korean patients with haemophilia.