The investigators will try to find any efficacy of platelet rich plasma injection for the treatment of osteoarthritis (OA) in the subtalar joint. Autologous platelet-secreted growth factors (GFs) may have therapeutic effects in OA capsular joints via multiple mechanisms. The investigators aim is to examine the effect of a platelet-derived preparation rich in growth factors(PRGFs) in OA of the subtalar joint, using parameters of pain, function, quality of life and safety.

The therapeutic use of autologous platelet-rich plasma (PRP) constitutes a relatively new biotechnology that has been a breakthrough in the stimulation and acceleration of soft-tissue and bone healing In this process PRGF (preparation rich in growth factors) combines the advantage of an autologous fibrin clot that will aid in hemostasis as well as provide growth factors in high concentrations to the site of a tissue defect. The platelet-rich plasma preparation encourages the release and slow delivery of growth factors from harvested platelets, activated by endogenous thrombin, and is used as a biological enhancer in the healing of fractures, lumbar fusions, cartilage defects, muscle tears and tendon lesions, thus promoting initiation and early maturation of bone and soft tissue formation which involves a more physiologic repair with less scar tissue.

Few tubes of whole blood are drowning from the patient in a sterile manner and go through a process of centrifugation and laboratory separation of the different plasma fractions. Then, to derive benefit from the described natural mechanism, Ca2+ is added to plasma enriched in platelets, triggering the formation of a fibrin matrix containing embedded platelets. The resulting PRGF allows the slow release of biologically active proteins that initiate and modulate wound healing in both soft and hard tissues .

The objective of this clinical trial is to evaluate the symptomatic efficacy of PRGF application in the treatment of OA of the Sub-Talar joint.

base on that knowledge here is the protocol briefly:

1st visit: Enrollment of patient

1. The patient will be given a full verbal and written explanation regarding the trial and treatment. by the investigator . The patient will sign the informed consent form and will be given a serial number.
2. The screening form :VAS SCORE and ANKLE-HINDFOOT SCORE will be completed-
3. Demographic data: date of birth, sex, age and complete medical history, weight, height and previous treatments will be recorded.
4. Clinical examination will be performed.
5. Blood (4 tubes, 4-5 m"l each) will be drawn from all patients . The blood taken from the PRGF group patients will then be used for the preparation of PRGF.

Intra-Articular injections (PRGF) will then be initiated.

TREATMENT PROCEDURES AND FOLLOW UP VISITS CLINICAL-RADIOLOGICAL ASSESSMENT

• Clinical assessment for all patients shall be made on enrollment, and then 4, 12, 26 weeks after enrollment.
• The clinical assessment will be according to the Ankle- Hindfoot, and the VAS SCORES.
• The radiological evaluation will be according to Kellgren and lawrence and will be performed on AP and Lateral views of the knee.

Side effect will be monitored at every visit

Inclusion Criteria:

• Male or female age 18-70
• Diagnosed OA of subtalar joint
• Patients who didn't benefit from other conservative treatments
• Patients who are willing to participate in the trial

Exclusion criteria:

• Non ambulatory
• Pregnant or lactating women
• Patient with containment disease that may affect joint
• Patient with open wounds; or skin disease; suspected joint infection: in the treated area
• Patients with a specific condition or poor general health status that will interfere with the functional assessments during the study or who had intraarticular injection or have had surgery within the previous 3 months