This prospective study will evaluate the hip function and quality of life of patients operated for total hip arthroplasty with Masterloc femoral stem and MPACT acetabular cup. The results of this study will establish the performance of Masterloc femoral component (Medacta International SA) and MPACT acetabular component (Medacta International SA), and provide a general estimate of survivorship, clinical effectiveness and complications.

Inclusion Criteria:

• Primary osteoarthritis of the hip necessitating primary hip replacement,
• Suitability for straight cementless stem,
• Adult male and female under 75 years old,
• Ability to give informed consent ,
• Patients who understand the conditions of the study and are willing to participate for the length of the prescribed follow-up.

Exclusion Criteria:

• Off-label use of the Medacta Masterloc femoral component and MPACT acetabular component
• Post-traumatic deformity in the affected hip,
• Patient suffering from Inflammatory arthritis including rheumatoid arthritis,
• Patient suffering by congenital or developmental deformity,
• Severe osteoporosis,
• History of surgery in the affected hip,
• Perioperative fracture,
• Personality disorders (dementia, alcohol or drug abuse etc) suspected of making completion of the trial uncertain,
• Patients with a history of active infection
• Pregnant women or those seeking to become pregnant

Patients undergoing surgery as part of routine care.