Study purpose is to evaluate perioperative usefulness of Platelet-rich Plasma (PRP) in total hip arthroplasty (THA) surgery. The study is designed as a randomized double blinded study using saline as placebo. The measurement outcomes includes objective variables (MRI, dynamometer) as well as subjective measurements (Oxford Hip Score, Harris Hip Score).

Patients are assigned to two different groups, according to a randomization list. PRP (approximately 9ml from which 1ml is delivered to in-house laboratory for the measurement of platelet count) is obtained from venous blood and applied to m. gluteus medius during the closure of modified lateral approach (Hardinge).

Study participants are evaluated preoperatively by trained physiotherapist. After surgery, participants undergo clinical evaluation and imaged (MRI) at 3 and 12 months post-operative. In the same time points, strength, Harris Hip Score and Oxford Hip Score. At the end of the study, the nature of the injected substance is revealed to the patients.

Inclusion Criteria:

• Clinically and radiology confirmed arthritis which treatment is total hip arthroplasty.

Exclusion Criteria:

• Revision surgery, insulin dependent diabetes and other endocrinology disease, smoking, use of per os cortisone, malignancy, rheumatoid arthritis, any autoimmune disease, alcoholist, previous fracture to hip, patients with diagnosed mental illness, absolute contraindications for MRI study