| Classification | Description | Comparison to normal hip |
| Grade 1 | Head displacement on neck <1/3 neck diameter | change in head-shaft angle <30o |
| Grade 2 | Head displacement on neck 1/3 – 1/2 neck diameter | change in head-shaft angle 30o-50o |
| Grade 3 | Head displacement on neck >1/2 neck diameter | change in head-shaft angle >50o |
Reference:
Boyer, D. W., et al. (1981). “Slipped capital femoral epiphysis. Long-term follow-up study of one hundred and twenty-one patients.” J Bone Joint Surg Am 63(1): 85-95.