Arthroplasty means remodeling of a joint, with or without the placement of a prosthesis. Synovencomy would refer to removal of a part of the membrane that encloses the joint (synovial membrane). These can be done for a number of indications. A few indications for arthroplasty incude osteoarthritis, rheumatoid arthritis, avascular necrosis, osteonecrosis, congenital dislocation of the hip joint, hip dysplasia , acetabular dysplasia, frozen shoulder, loose shoulder, joint stiffness, severe dislocations, traumatized joint, growths/ malignancies etc. Likewise synovectomy can be done for severe rheumatoid arthritis, juvenile idiopathic arthritis, haemarthrosis, synovial osteochondromatosis, synovial chondromatosis, pigmented villonodular synovitis etc. It may not be possible to correctly identify all lesions on the MRI. A direct visualization through a scope is always better than imaging studies. Recovery in most cases follows like any other surgery depending on the exact procedure that was done. It would be best to discuss this in detail with your orthopedic surgeon.
Hope this information was useful.