ACL Injuries, Knee Surgery & Robotic Surgery — with Dr. Kow Ren Yi (ALTY)

In this episode of the Medifly Podcast, the host — a three-time ACL tear patient — speaks with Dr. Kow Ren Yi, a consultant orthopedic and robotic joint surgeon at ALTY Orthopedic Hospital in Kuala Lumpur, about when surgery is truly necessary, how to evaluate surgeons and treatment options, and what robotic technology can and cannot do. Dr. Kow Ren Yi explains the critical differences between joint-preserving and replacement surgeries, the importance of understanding the root cause before any revision procedure, and why techniques such as kinematic alignment and partial knee replacement remain underused despite strong evidence. The conversation also covers the long-term consequences of untreated ACL injuries, who genuinely benefits from stem cell therapy, and emerging research into weight management and gut health as tools for preventing osteoarthritis.

A Medifly Podcast Conversation with Dr. Kow Ren Yi, Consultant Orthopedic & Robotic Joint Surgeon, ALTY Orthopedic Hospital, Kuala Lumpur

Introduction

Kevin (Host): I've torn my ACL three times in my life. I've had two different surgical techniques. The third tear — my worst one — I chose to leave untreated. Which brings me to today, and a very important conversation about not just orthopedics, but something that has been impacting my health for a very long time.

My name is the host. I'm the co-founder of Medifly, and this is the Medifly Podcast. My guest today is Dr. Kow Ren Yi, Consultant Orthopedic and Robotic Joint Surgeon at ALTY Orthopedic Hospital in KL — one of Malaysia's first single-specialty orthopedic hospitals. Dr. Kow Ren Yi graduated as a top clinical specialist in his cohort with a Master's in Orthopedic Surgery. He is an active researcher with a growing body of published work on robotic joint surgery and has served as an editor at the Malaysian Orthopedic Journal.

From everything I've read of his public writing, he is one of those rare surgeons who actually talks openly about what medicine costs, when a scan is needed and when it isn't, and when technology genuinely helps versus when it is just marketing. That is honestly why I wanted him on the show.

Today we'll be covering:

1. What actually separates a great orthopedic surgeon from a good one
2. Where robotic surgery genuinely changes outcomes — and where it is overhyped
3. What happens long-term to knees that have been injured, repaired, and sometimes left alone
4. The questions every patient should be asking before they let a surgeon anywhere near their joints

The Doctor's Origin Story: From Personal Injury to Orthopedics

Kevin: Most surgeons pick their specialty based on something personal — a mentor, a pivotal case. What pulled you specifically into joints and orthopedics?

Dr. Kow Ren Yi: My experience is actually quite similar to yours. I personally experienced an orthopedic problem before — I had a fracture of the femur, the thigh bone, during my teenage years. That kind of hooked me towards orthopedics. Since I was young I had been doing some reading on it, because I myself experienced that problem. That got me into medical school in the first place, and in medical school I was already being exposed to bone and joint diseases. Since graduating as a medical doctor, I further specialised in orthopedics, becoming one of the younger surgeons in the field. My mentors specialised in arthroplasty — joint replacement — and that further enhanced my interest. That is how I ended up as an arthroplasty surgeon.

Why Research Matters in Clinical Practice

Kevin: You are clearly very busy with clinical practice, but you're still deeply involved in research and journal editing. A lot of surgeons drop the academic side when they go private. Is there a reason why you continue?

Dr. Kow Ren Yi: Clinical practice is very important, but your clinical practice all boils down to the underlying knowledge behind it. Whenever you are performing a surgery, you need a deep understanding of the knowledge, the skills, the know-how, and most importantly the physiology and underlying disease before you address the problem.

"What we are dealing with in diseases — only 20% of them are known. The other 80%, which is largely beneath the surface, are still unknown. So there are still a lot of things unknown in medical fields, especially in orthopedics."

This is why I am actively involved in research — to get to know more about diseases so that we are better able to help our patients.

Understanding the Patient: Joint Preservation vs. Joint Replacement

Kevin: If I am a patient coming in for knee or hip surgery, what is one question that is often overlooked?

Dr. Kow Ren Yi: It depends on the patient's profile. If we are looking from a younger perspective — and when we say young, we mean 50 years and below — then we are looking at joint-preserving surgeries. If we are talking about a patient who is 50 years and above, we are considering replacement surgeries. These are two very different patient profiles.

For younger patients, the issues are mainly ligament problems such as ACL tears, meniscus problems, and cartilage problems. When we examine the patient, we need to know what is the underlying problem causing the knee pain — and by addressing that root cause, then only can we address the problem properly.

For elderly patients aged 50 and above, we are looking at the stage of disease progression. If it is a mild-to-moderate stage, we try joint-preserving alternatives first. For those with very severe deformities affecting their activities of daily living, then we are talking about joint replacement surgery.

Robotic Surgery: Genuine Benefit or Overhyped Marketing?

Kevin: Robotic surgery is marketed very frequently — you see posters everywhere. Cut through all the marketing: when does robotic surgery genuinely change the outcome, and where is it honestly overhyped?

Dr. Kow Ren Yi: Robotic surgery definitely helps surgeons, but it is actually a tool that assists the surgeon — not one that replaces the surgeon. It depends entirely on how the surgeon uses the robotic system. It is just like a knife for a surgeon: if you use it correctly, you can perform a very precise surgery. But if you are not skilled enough, you might cut the wrong things.

"Robotics can provide a false narrative that the surgery will be perfect. It all boils down to the person behind the robotic system — which is the surgeon."

For myself, I am trained in four different robotic systems, which is how I understand the pros and cons of each. Depending on the patient's profile, I use different robots to help my patients. I have performed more than 300 cases using robotic systems, and that is how I gather experience.

The Advantage of a Single-Specialty Hospital

Kevin: ALTY is a single-specialty hospital — eight orthopedic surgeons under one roof, with weekly multidisciplinary case reviews including anaesthesiologists, physiotherapists, and cardiologists. Most private surgery happens in multispecialty hospitals with surgeons as solo operators. What does that structural difference actually mean for patient outcomes?

Dr. Kow Ren Yi: The single-specialty hospital concept helps our patients more because our patients are mostly of the same demographic, with the same kinds of problems, and they undergo the same types of surgeries. This means our supporting staff understand their disease progression and their rehabilitation protocols deeply.

In a general hospital, a physiotherapist is exposed to everything — heart disease, lung disease, upper limb, lower limb — so they need to know everything, but are an expert in nothing specific. In our hospital, our physiotherapists are trained to do that one task only: to help orthopedic patients recover. So our patients get specialised care not only from the surgeons, but from every member of the supporting team. That really helps outcomes.

ACL Tears: When to Operate, When Not To, and Understanding Revision Surgery

Kevin: I've torn my ACL three times and my meniscus once — right leg in 2017, left leg in 2020, and a third time in October 2023. When would you recommend a patient undergo surgery, and when would you recommend against ACL surgery?

Dr. Kow Ren Yi: When we encounter a situation like this, we are talking about revision surgery. The most important first step is to identify what caused the previous surgery to fail. There is no point repeating the same mistake — if you go for a revision surgery without understanding the root cause, the revision surgery may fail as well.

"You need to understand what caused it to fail in the first place — then only can we address the subsequent problem. There is no point if you repeat the same mistake."

Was it too fast a rehabilitation protocol? Was the graft size inadequate? Was there a fault in the mechanical alignment? These are all factors that must be addressed before embarking on revision surgery.

In a young patient like yourself, we try to preserve whatever native structures remain — in this case, the anterior cruciate ligament (ACL). The ACL is critical for maintaining knee stability. When the ACL is ruptured, the knee loses stability, and that instability causes two things:

1. Every time you walk or run, it causes damage to the surrounding structures — especially the meniscus and the cartilage.
2. Over time, this degenerative damage compounds and causes early osteoarthritis.

So the clinical process for a revision case would be: first identify the root cause; second, examine for any associated injuries to the meniscus and cartilage; third, perform an MRI to evaluate radiologically; and then discuss the treatment plan — which in this case would be a revision ACL reconstruction.

Graft Options for ACL Reconstruction: Autograft, Allograft, and Synthetic

Kevin: The graft doesn't have to come from my own body?

Dr. Kow Ren Yi: Correct. When the ACL is ruptured, we perform a reconstruction surgery, meaning we replace the ACL with something new. There are a few graft options:

• Autograft: Harvested from your own body — either the patellar tendon or the hamstring tendon.
• Allograft: Harvested from a cadaveric donor. This is used when all autograft options have been exhausted, as in a revision scenario.
• Synthetic (Ligament Augmentation Device / Biobrace): Used in combination with an autograft when the graft size is inadequate. Generally, we want a graft diameter of at least 8 mm. If the harvested graft is smaller than that, the Biobrace is added to increase the diameter — because an inadequate graft size increases the risk of failure. That may, in fact, be one of the reasons for a previous ACL reconstruction failing.

What Does an Untreated ACL Tear Mean for the Future?

Kevin: Looking 20 to 30 years down the road, what does my knee look like at 55 or 65? Is there anything I can do now, at 32, to change that trajectory?

Dr. Kow Ren Yi: We need to look at this from two perspectives.

The first is the initial injury itself. The very first ACL tear is an insult to your knee — whatever damage has been done, even if you subsequently undergo a perfect surgery and achieve 100% return to sport, that first insult still carries a risk of developing osteoarthritis in later years, particularly in the 50s.

What is osteoarthritis? It is a degeneration of the knee joint where the cartilage on the thigh bone and the shin bone has already worn off. It is very common in the elderly population, especially those aged 55 and above — up to one-third of them will develop it. Given your history of injury, your risk is even higher.

By performing surgery, we can reduce that risk — not to zero, but meaningfully reduce it. When you sustain a second or third injury, those risks compound. An untreated ACL rupture leaves the knee unstable, which — as we discussed — damages the meniscus and cartilage over time, further accelerating the path to an osteoarthritic state.

"We want to delay the knee from getting into the osteoarthritic state as much as possible — because when you reach stage three to stage four, we are talking about replacement surgery."

Three Questions Every Patient Should Ask Before a Knee or Hip Replacement

Dr. Kow Ren Yi:

1. "Are there any alternatives?" A surgeon who does not offer any other alternatives does not know the problem well enough. You should understand the full spectrum of treatment options — from non-surgical approaches to minimally invasive procedures, all the way to the most invasive. The right treatment depends on the stage of disease.

2. "What are the pros and cons of each option?" Every patient is different — their medical conditions, their activity level, and their expectations all vary. Only when you can assess those factors together can you determine the most suitable treatment plan.

3. "Have you performed this specific procedure before, and can you show me outcomes?" A reputable, experienced surgeon will be able to share real case examples — clinical results, imaging, and patient recovery — so that you know what to expect. You can also search the surgeon's name online; a surgeon who is well known and reputable within the orthopedic community will have a visible, verifiable professional record.

Partial vs. Total Knee Replacement: A Crucial Distinction Most Patients Miss

Dr. Kow Ren Yi: When people talk about knee replacement, they almost always only talk about total knee replacement — where we replace the entire surface of both the thigh bone and the shin bone. This is indicated when the cartilage damage has involved all compartments of the knee joint.

What most patients — and many doctors — do not know is that there are joint-preserving surgeries such as partial knee replacement, where we replace only half of the joint. When we actually perform surgery, we find that in the majority of patients the cartilage wear is located only on the inner side of the knee joint — the outer side remains intact 90% of the time. If you perform a total knee replacement in that patient, you are replacing perfectly healthy cartilage unnecessarily.

The key advantage of partial knee replacement is that we preserve all the ligaments — most critically the ACL and PCL — retaining full joint stability without sacrificing intact structures.

"A lot of patients don't know about partial knee replacement because even doctors themselves, most of them don't know how to do it. So they skip this treatment — they give injections multiple times until the knee becomes so severe that they do a total knee replacement. They skip this stage altogether because they don't know how to perform it."

In patients who have undergone partial knee replacement, 95% can walk on the same day or the following day.

Stem Cells and PRP: Who Actually Benefits?

Kevin: A lot of people travel abroad — to Thailand and elsewhere — to get stem cell injections after surgery, hoping to heal faster. What is your view on that?

Dr. Kow Ren Yi: Stem cells do help — but you need to understand the underlying basis before applying any treatment. We are again looking at two cohorts.

For younger patients, we are trying to preserve and regenerate native structures. This is where treatments like stem cells and PRP (Platelet-Rich Plasma) are applicable. These are regenerative and rehabilitative in nature — they stimulate inflammation, which in turn promotes cartilage regrowth. This is appropriate for younger patients.

For older patients, particularly those aged 55 and above, these treatments are generally not effective. Their metabolism is slower and their regenerative capacity is much lower compared to younger populations.

So stem cells, PRP, and prolotherapy are not very effective in the elderly population. The key is knowing for whom these treatments are indicated — they should not be given indiscriminately to all patients.

Dr. Kow Ren Yi's Current Research: Kinematic Alignment in Knee Replacement

Kevin: Can you tell us more about the research you are particularly interested in?

Dr. Kow Ren Yi: I am mainly involved in research dealing with hip and knee diseases. I am a member of a research group analysing knee phenotypes and how robotic surgeries assist patient recovery. I am particularly interested in how different alignment techniques affect patient outcomes after knee replacement.

In conventional total knee replacement, surgeons typically use mechanical alignment — restoring the joint to a precise 90°/90° angle at the thigh bone and shin bone, producing a very straight knee. However, studies show that 98% of the population do not naturally have this exact 90°/90° alignment. This is why many patients, even after a technically successful total knee replacement, experience pain and an unnatural feeling in the knee.

The technique I practise is kinematic alignment — restoring the knee joint based on the patient's own native anatomy, rather than a standardised geometric target. My initial results show that patients who undergo kinematic alignment have less pain, faster recovery, and a more natural feeling in the short term after surgery. Robotic systems support this by enabling bone cuts accurate to 0.01 mm — because the precision of the bone cut determines exactly where the metallic implant sits.

The Future of Orthopedics: What Patients Should Know

Kevin: Looking five years ahead, what is coming in orthopedics that most patients don't yet know about?

Dr. Kow Ren Yi: I am quite hopeful about the future.

The first development is in weight management. New injectable and oral therapies for obesity have shown great promise. Weight control is critical for joint health — reducing body weight reduces the stress and forces transmitted through the hip and knee joints. Some patients with osteoarthritis have even become asymptomatic — pain-free — after significant weight reduction.

The second emerging area is gut health and the microbiome. Most people focus on supplements like chondroitin and glucosamine — which are building blocks for cartilage. But what is less understood is what triggers the inflammation that leads to osteoarthritis in the first place. Early studies are pointing toward the role of gut flora, and how probiotics may help prevent or reduce that inflammation. This is still at an early stage, but it represents an exciting shift toward preventive medicine — preventing osteoarthritis before it develops.

Closing Remarks

Kevin: Dr. Kow Ren Yi, thank you very much. I came into this conversation with my knees in mind, and I'm leaving with a much better understanding of what it means to have knee surgery and what the next 20 years might look like for me.

For anyone listening who wants to learn more about Dr. Kow Ren Yi's work, he is at ALTY Orthopedic Hospital in Kuala Lumpur — I'll link everything in the show notes. And if you've been putting off a joint consultation, or are researching surgeons for a family member, this is exactly what Medifly exists for. We don't match patients to hospitals — we match patients to the right surgeon for their specific case. Find us at metafly.ai.

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