Orthopedic surgeons at NewYork-Presbyterian/Columbia are working to advance understanding and diagnosis of anterior knee pain (AKP) in patients who have undergone total knee arthroplasty (TKA). Recently, Roshan P. Shah, MD, Director of Complex Adult Hip and Knee Reconstruction at NewYork-Presbyterian/Columbia, authored a critical review and appraisal of the literature surrounding AKP in the unsatisfied, difficult-to-diagnose, and well-appearing TKA.
The paper, published in JBJS Reviews, focuses on less commonly considered and investigated sources of AKP, particularly those related to soft tissues. “Much of the literature focuses on radiographic variables such as anterior overstuffing, patellar obliquity, component malpositioning, loosening, and instability as modifiable causes of AKP,” notes Dr. Shah, an orthopedic surgeon who focuses primarily on knee and hip conditions. “What we have come to understand in our review and in practice is that the soft tissues around the knee are underappreciated as the proximate cause of AKP.”
Addressing Limited Understanding of AKP
In their review, which assessed evidence from 53 studies comprising thousands of TKA cases, Dr. Shah and colleagues observed that AKP remains incompletely understood. “The art of TKA surgery started with a rudimentary understanding of the knee and with undeveloped instruments of surgery. Now, we have a lot more information, with robotics and other high-tech tools in the operating room that allow us greater precision to add nuance to standard TKA techniques,” he observes. “As a result, we see better outcomes in lots of people who feel great, who can kneel, who can have almost normal knee function. And yet, we as a profession hold onto the standard techniques longer than we should because of reverence for the legendary surgeons who created them.
“Anterior knee pain remains poorly understood and inadequately studied because researchers haven’t thought outside of the box in a lot of cases,” he continues. “We don’t have to accept that up to 20% of patients will have dissatisfaction with their TKA. We should strive to improve and evolve our surgical techniques, especially so that we don’t see AKP as often.”
Anterior knee pain remains poorly understood and inadequately studied because researchers haven’t thought outside of the box in a lot of cases. We don’t have to accept that up to 20% of patients will have dissatisfaction with their TKA. We should strive to improve and evolve our surgical techniques, especially so that we don’t see anterior knee pain as often.
— Dr. Roshan P. Shah
Dr. Shah surmises that soft-tissue-related causes of AKP after TKA are underappreciated because they are not visible on an x-ray. “Historically, x-rays are the main kind of outcome measure that we have as surgeons, but studies looking at bone and alignment haven’t completely answered our questions,” he explains. “In my own training and my own experience of doing knee replacements, I’ve always questioned the little things that are easy to ignore. For example, we rarely talk about the articularis genus, a small muscle on the top of the lining of the knee joint. In many traditional techniques we just cut right through it on entry to the knee, but it is an important muscle and can have a profound impact on outcomes. By respecting it, staying away from it and not cutting through it, we have been able to reduce anterior knee pain. Those kinds of experiences made us ask more questions about soft tissue.”
Dr. Shah has worked closely with Clark T. Hung, PhD, Professor of Biomedical Engineering and Professor of Orthopedic Sciences at Columbia, who has developed a 3D model that encompasses the entire structure of the knee including bone, cartilage, synovium, and nerve endings. “Using that model, we can look beyond just the cartilage and bone, and really appreciate the effect of soft tissues like the articularis genu acting on the synovial lining of the joint and the generation of inflammation and pain and the other symptoms of arthritis.”
The 3D model has helped Dr. Shah refine his surgical approach. “In the early stages of my career, I followed all the classic teachings and edicts, making sure I didn’t overstuff the patella, externally rotating the femur to an abnormal position, and changing normal mechanics,” he says. “Recently, I’ve switched to embracing and pursuing a more anatomic reconstruction, using the metal of the implant to essentially replace what’s being removed, but accounting for the divots and potholes of cartilage wear from the disease. I adhere to a minimally invasive surgical approach, one designed to minimize damage to the tissues. I fully resect all the nerve endings in the synovium, reconstruct the kneecap to a natural thickness of anywhere from 22 to 26 millimeters, resect the lateral patella osteophyte, burn the nerves on the lateral patella, and then most importantly, reconstruct the knee in a way that’s anatomical, with neutral rotation of the femoral component and the obliquity of the joint line, and filling and better balancing the flexion space. This way, the kneecap and tendons are not overly stretched on the lateral side when bending—which seems to reduce AKP. Use of the technology and robots has made all that a whole lot easier.”
Addressing Heterogeneity in Surgical Techniques
Whereas techniques such as patellar denervation and resurfacing are commonly used in TKA, results have been mixed. Dr. Shah suggests that is due to wide variability in individual surgeons’ approaches. The same problem pertains to studies of surgical techniques. “Even if you get some consistency from a single surgeon, you get the criticism of, how valid is it externally to other patients? And then if you’re combining surgeons, even in the same institution, it’s the same surgery and the same implant goes in, but it’s a very different technique from one surgeon to another.
“Our challenge in orthopedics is trying to get answers and truth from comparing very heterogeneous techniques and procedures,” Dr. Shah continues. “When you’re studying 300 variables, it’s really hard to isolate one variable, especially when you combine patients from different surgeons. In theory, patellar denervation – using electrocautery to burn the nerves around the kneecap – should work. One surgeon may go a lot deeper than another. One surgeon may go circumferential, where the quad and patellar tendons are, whereas I would jump out of my skin if I saw that happening because I want to stay away from risking the most important functional tendons in the knee. The approaches can be totally different but they’re all called the same thing, making it hard to get a clear answer.”
If we’re going to get to get to a place where people feel normal after a knee replacement, we have to respect and honor the soft tissues.
— Dr. Roshan P. Shah
Similar limitations apply to the study of minimally invasive procedures. “If you take just the most skilled one or two people in the world, you’d say, ‘Wow, this is incredible. Everybody should do it this way,’” Dr. Shah comments. “But the reality is not everyone can do it that way. It can be harmful to patients in the wrong hands. So it’s not necessarily about the principles of minimally invasive procedures. If we’re going to get to get to a place where people feel normal after a knee replacement, we have to respect and honor the soft tissues.”
Refining Future Research Approaches
In their paper, Dr. Shah and colleagues call for further research into intraoperative management of synovium and other soft tissues. “We don’t have excellent, well-controlled studies to answer questions about these tissues, to understand more effectively the relative weight and emphasis on variables such as patellofemoral stuffing,” he says. “Every knee is different. Some are knock-kneed, bow-legged, worn in both directions, or only in the patella. Some have very limited range of motion, some are full and loose. Some people have naturally loose ligaments, some are super tight. You can’t compare; they are like apples and giraffes.
“But let’s say we were able to design studies where we had the same type of arthritis, similar range of motion, similar phenotype of knee, similar angles for the joint, and then just change one variable,” he continues. “In a perfect world, we would have that level of study or a good basic science version that we can use to answer these questions. We’re still struggling with the design to get a very rigorous, well-controlled trial.”
At NewYork-Presbyterian/Columbia, Dr. Shah and his colleagues create a culture of innovation and collaboration to give patients the best outcomes possible. “The fact that we’re doing so much synovial research at a very basic science level with the bioengineers is a real tribute to our program, our hospital, and our university,” he remarks. “The surgical translation of that basic work is something you can’t get without having that experience. We have a group of really innovative thinkers who question all the foundational tenets of knee and hip replacement so that we can use every surgery and outcome as a valid piece of data, learning and growing from each case. We’re at an academic institution, we’re researchers by nature, we’re surrounded by innovative and creative people in the university, and we’re asking these questions on a daily basis.”
We have a group of really innovative thinkers who question all the foundational tenets of knee and hip replacement so that we can use every surgery and outcome as a valid piece of data, learning and growing from each case.
— Dr. Roshan Shah
“It all contributes to a more evolved experience for knee replacement, compared to the traditional experience offered elsewhere,” Dr. Shah concludes. “The nice thing about NewYork-Presbyterian is they’ve embraced technology and allowed us to reach that next level of precision. Things like robotics, sensor technology, and custom implants all contribute to our ultimate goal of giving people a normal experience and not a many months-long recovery.”
