The perichondrium is primarily responsible for the strength of the proximal femoral physis SCFE differs from a displaced Salter I fracture in that the perichondrium remains intact in most cases of SCFE and is disrupted with acute Salter I fractures Collagenous bridges that traverse the physeal cartilage and the undulating convexity of the physis toward the epiphysis contribute to the shear strength across the physis Children with more vertically inclined physeal angles have greater shear stress across their proximal femoral physes and therefore are at greater risk for SCFE Although it takes an enormous shearing force to produce acute slippage of an initially normal hip joint, the viscoelasticity of the physeal cartilage allows for gradual slippage Most children with acute presentations will also have radiographic evidence of chronic slippage SCFE is classified by symptom duration, stability, and degree of displacement Patients with acute SCFE have symptoms for less than weeks; with chronic SCFE, symptoms are present for more than weeks Acute-on-chronic SCFE describes patients with symptoms for more than weeks with a recent exacerbation An acute slip with severe symptoms is unstable Acute or chronic slips with mild symptoms are stable and have a more favorable prognosis SCFE is idiopathic in about 95% of cases Endocrine disorders, hypothyroidism in particular, renal failure and radiation therapy are risk factors for “atypical SCFE.” Children outside the usual age range for SCFE, children with valgus displacement of the femoral epiphysis, and those with other signs and symptoms that suggest possible endocrine abnormalities should be referred for endocrine evaluation Clinical Considerations Clinical Recognition Pain and/or limp are the most common chief complaints in patients with SCFE Physicians may be misled when the pain is referred to the groin, thigh, or knee which occurs in over 40% of cases Triage The presence of limp or hip pain and the potential for SCFE is rarely an emergent condition These patients should remain nonambulatory as continued weight bearing may exacerbate the slip The presence of fever in the setting of hip pain or limp would not be consistent with SCFE but may suggest a septic arthritis or osteomyelitis and therefore warrants a higher triage level Initial Assessment/H&P