The purpose of this study is to describe the 3D joint biomechanics of the lower extremities of patients having had a total hip replacement or hip resurfacing surgery as compared to a healthy age and weight matched control group during level walking, stair ascent and descent, and entering and exiting the front seat of a car.

Much research has shown that patients are generally satisfied with pain relief in the months and years following a total hip replacement (THR) or hip resurfacing procedure. However, many express dissatisfaction with their ability to perform daily activities, a reduced walking ability and long-term lower extremity muscle weakness. Given the general lack of knowledge surrounding joint motion of the lower extremities in the THR population, there is a need to characterize the joint mechanics of people having undergone THR, so that interventions and rehabilitation strategies can be designed to reduce post-operative complications and improve mobility.

Inclusion Criteria:

• 15 patients between the ages of 50 and 75 yrs having undergone a primary total hip replacement or hip resurfacing within 6 to 18 months of the study will participate, as well as an equal number of age, sex, height and weight matched healthy control participants.

Exclusion Criteria:

• Potential participants for the control group will be asked if they have had previous lower limb ailments or surgery, and if they have they will be excluded. Moreover, the THR participants cannot have had secondary hip replacement due to infection, revision surgery, or a concomitant surgical procedure (i.e., graft). Participants from both groups cannot have had any medical conditions which could affect physical movement such as a stroke.