The Arthrosurface Meniscal Sparing Unicondylar knee system is a surgical method for the treatment of localized cartilage lesions and defects in the major joints . This system is comprised of three elements; a three-dimensional mapping technology, a set of instruments to map and prepare the damaged area and a cobalt-chrome and titanium implant. The system precisely aligns the surface of the implant to the contours of the patient's articular cartilage surface, thus filling the defect and restoring a smooth and continuous articular surface. The UniCAP Instrument Set enables the surgeon to accurately place the implant and precisely map the curves of the articular surface, in real-time, under direct or arthroscopic visualization, with no angle-induced errors or magnification errors that might exist with MRI, or X-ray imaging techniques. The UniCAP system is intended to provide an effective interim means for managing pain and disability in the middle-aged patient until a total joint replacement treatment option becomes more necessary, and is part of a clinical treatment strategy to help avoid early-age-revision scenarios. The prosthetic may also provide a treatment option for the older patient who may not tolerate the morbidity of a total joint replacement procedure.