This study was performed to evaluate the width of symphysis pubis and its radiographic appearance in different age and sex, and it was aimed to establish a radiographic diagnosis criteria for diastasis of the joint.

The width and the appearance of symphysis pubis were observed by pelvic X-ray in 92 males and 169 females who had no history of any joint disease. The mean width of symphysis pubis was calculated and data were analyzed by age, sex and parity using student t-test.

The mean width of symphysis pubis was 2.88±0.71 mm in male group and was 3.24±0.68 mm in female group. It was 3.34±0.84 mm in parturient and 2.82±0.55 mm in nullipara and the difference between these two groups was significant (P<0.05). Osteoarthritic changes were noted in most cases over 60 irrespective of sex.

Based on the results from this study and reported value of physiological relaxation of symphysis pubis through pregnancy and labor, a separation over 6 mm and/or a vertical migration over 3mm can be diagnosed as diastasis of symphysis pubis. This criteria would facilitate the earlier diagnosis of relaxation and separation of this joint by labor or trauma.