Musculoskeletal outcome remains the major hallmark of haemophilia. The purpose of the study was to assess joint status using a new musculoskeletal assessment tool in children with haemophilia and describe the development of haemophilic arthropathy during childhood and puberty focussing on the age of remarkable changes. The prospective study involved Lithuanian patients aged 4-17 years with severe haemophilia A and B, no signs of inhibitors and treatment on-demand. Patients were subdivided into two groups according to actual age. Group I patients were 4-9 years and group II patients 10-17 years of age. The musculoskeletal status was measured using the Haemophilia Joint Health Score (HJHS). We report on 20 patients with a mean age of 11.5 years (SD 4.3, range 4-17.2 years). The mean HJHS score was 24.5 (SD 14.5, range 5-50). The most affected joints were ankles, followed by knees and elbows. Mean HJHS score in age group I (n = 7) was 11.6 (SD 6.5); in group II (n = 13) the score was significantly higher - mean 31.5 (SD 12.8) (P = 0.0002). Ankles, knees and elbows were significantly more impaired based on the HJHS scores in older patients as compared with younger ones. The HJHS appears to be a useful tool in evaluating musculoskeletal outcome of patients receiving treatment on-demand. Children > or =10 years of age had significantly higher HJHS scores as a sign of progressing haemophilic arthropathy. We conclude that the most aggravating development of haemophilic joint damage seems to occur from the age of 10 and onwards.