summary THA Leg Length Discrepancy is a common finding following THA that may be transient due to weakness of the abductors or permanent due to intentional limb lengthening. Diagnosis can be made clinically with comparison of the measurement from the anterior superior iliac spine to the medial malleolus. Pelvic radiographs can also be used to determine and compare limb lengths. Treatment is generally observation as most cases resolve with relaxation of the abductor muscles over time. Shoe-lifts may be indicated if leg length discrepancy persists after 6 months. Epidemiology Associated conditins 2nd most common reason for litigation following total hip arthroplasty (following nerve injury) Etiology Mechanism contracture leads to pelvic obliquity ABDuction contracture causes involved hemipelvis to be lower, creating apparent LONG leg ADDuction contracture causes involved hemipelvis to be higher, creating apparent SHORT leg weakness weak abductors may provide the sensation of a long leg in the absence of true LLD usually resolve within 3-6 months post-operatively Prevention pre-operative planning reduces incidence of post-operative discrepancies Presentation Symptoms patient may feel perceived LLD despite anatomic equality Physical exam post-operative assessment of limb-length discrepancy true limb length measured from anterior superior iliac spine to medial malleolus apparent limb length determined by adding effect of soft-tissue contractures and pelvic obliquity difficult to truly measure Imaging Radiographs recommended views AP findings leg length discrepancy increased neck length increasing femoral offset will not increase limb length Treatment Nonoperative shoe-lift indications shoe-lift adequate in most cases wait 6 months until treatment to allow adequate relaxation of muscles Operative revisions THA - rare indications significant LLD that affect quality of life and has not resolved over 6 to 12 months. concern for dislocation with revision surgery especially if attempting to shorten limb