Slipped capital femoral epiphysis (SCFE) is a well-known disorder of the hip in adolescents that is characterized by displacement of the capital femoral epiphysis from the metaphysis through the physis. Multiple theories have been proposed for the aetiology of idiopathic SCFE, and it is likely a result of both biomechanical and biochemical factors. The association between human leucocyte antigen (HLA) and certain rheumatic diseases is well established. One of the strongest associations is between the HLA class I antigen B27 and ankylosing spondylitis. Several DRB 1 alleles are associated with susceptibility to and severity of rheumatoid arthritis. The quest to find similar markers have fuelled the suggestion that SCFE may be linked to the presence of a specific HLA antigen. We present a case report of an identical twin presenting with SCFE. An 11-year-old girl presented with pain in her hip for last few days and difficulty in mobilizing. Radiographs showed SCFE that was fixed in situ with one screw. Eighteen months later her twin sister presented with pain in hip and limp of 3-week duration with no preceding history of trauma. Radiographs showed SCFE that was fixed in situ with one screw. Both sisters have made full recovery with no pain or residual limp. HLA typing of the twins showed variations between diseases and HLA phenotype in different population groups with SCFE. This is the fifth case of identical twins presenting with SCFE with HLA class I analysis and only the second case report with both HLA class I and class II analysis. Our case report further emphasizes findings from previous studies that there is no relationship between SCFE and a specific HLA class I or class II antigen. Level of evidence: Level V.