# Potential New Treatments for Knee OA: A Prospective Review of Registered Trials
## 4 Discussion
### Knee Replacement  
In our analysis, knee arthroplasty was the most investigated topic. There were several trials investigating the differences between single and multi radius femoral component designs. Current designs have matured over many years with minor adjustments. They produce 90-95% survival at 15-20% and good clinical outcomes measured by patient reported outcomes for the majority of the patients (approximately 85%) [15; 16; 17]. The multi radius was introduced many years ago and aims to restore the natural \"J\" shape of the femoral condyles. In the normal knee, this functions in synergy with the femoral roll-back to offer stability, strength, and improved flexion. The single radius places the center of rotation more distal and posterior. It attempts, at least in theory, to provide more lever arm for the extensor mechanism and thus improve strength. Current evidence did not show any significant differences between these two femoral component designs regarding functional outcomes [18]. Another studied topic was the medial congruence. The natural knee has a stable medial compartment and a more mobile lateral. Some new implants attempt to replicate this by using a modified polyethylene design and studies are under way to evaluate possible benefits. Cementless fixation lost in popularity, but in our analysis we found a renewed interest. This is probably generated by younger patients receiving knee replacements and improved implant manufacturing. Current knee arthroplasty systems use cemented fixation as golden standard. There is an ongoing debate over the superiority of cementless fixation. There are many aspects of arthroplasty which contribute towards outcomes and survival in very large cohorts such as national registries [19; 20]. In theory, the roughened, porous surface of the knee implants may provide optimal bone ingrowth which in turn will produce a durable fixation. Unfortunately, early cementless implants had many issues which led to early loss of fixation and subsidence, especially on the tibia, due to poor geometry and ineffective osteoinductive surfaces [19; 20]. A recent meta-analysis found no difference in revisions and function between cemented and cementless knee replacements up to 16.6-year follow-up, based on current literature [20]. Knee arthroplasty addresses pain, restores range of motion, and corrects limb deformity. The primary prosthetic implants are stabilized by the knee's envelope of ligaments and mobilized by the extensor mechanism. Accurate positioning of the implant will lead to improved function and longer survival [7; 9; 17]. Classic systems use anatomic guides and surgeon experience. Navigation and patient specific cutting guides were later introduced but failed to prove their utility. We now can use 3D preoperative planning, integrate ittogether with intraoperative mapping of the bone contours and have the surgeons assisted by a robotic arm to make the bone cuts and establish ligamentous balance [9; 17]. Several points have impaired the expansion of robotic surgery in knee arthroplasty. Robotics are at the beginning but have not significantly improved these numbers. They may improve rotational and coronal alignment but with added hassle of having the cumbersome robot in the room, maybe a technician, additional steps for referencing the robot to the patient and most importantly added costs [17; 21; 22; 23]. Partial (unicondyl) knee replacements replace just the medial compartment, which is more often damaged by OA. These prostheses are less invasive to implant and produce comparable outcomes to total knee replacements in selected patients [9; 17]. However, they were plagued by higher revision rates compared to total knee designs. It may be that by only partially replacing the joint through a limited approach, the positioning of the components is not optimal. This is where robotic assistance already shows fewer complications (RR: 0.52, \(p\) = 0.036) and lower revision rates (RR: 0.42, \(p\) = 0.017) [17; 24].