Blog Post

Interview With a Knee Expert: Dr. Sabrina Strickland

Dr. Sabrina Strickland, MD is an orthopedic surgeon at the world-renowned Hospital for Special Surgery (HSS). She specializes in treating conditions of the knee, particularly those affecting the patellofemoral joint (the joint between your kneecap and thigh bone). 

In fact, she is a co-founder of HSS’s Patellofemoral Center. She is an associate professor of orthopedic surgery at Weill-Cornell Medical College. Additionally, she has some legitimate athletic bona fides as she has skied most of her life and was a ski instructor in Colorado. She and her family continue to ski every year.

I got the chance to speak with her for a bit, so I asked her some questions that I think would be useful for our patients.

Zach: When someone gets knee pain, what should clue them in that it’s time to see a physician?

Dr. Strickland: First of all, if there’s an injury, an actual event, and it’s altering their gait or affecting their weight-bearing. Additionally, some people are bad at judging swelling, but certainly if it’s obviously swollen that should be an indication you need to get it checked out.


What’s the best advice you have for the average runner out there to prevent running-related knee pain and injury?

Most important is cross-train. I’m sure you see so many patients who just started running and all they do is run. I think they’re chances of actually succeeding in running a half or full marathon are much lower than people who do resistance training or some other types of exercise classes.

Check out some of Gotham PT’s favorite strengthening exercises for runners

You are an avid skier, and ski season could be considered “ACL season” for the number of ACL (anterior cruciate ligament) injuries that occur during that time. Is there anything people can do to prevent ACL injuries while skiing, or is it just bad luck?

I think the real answer to that is bad luck. Most of the injuries I see are not high-energy injuries, not that you can necessarily prevent high-energy injuries. Most of the ACL injuries I see are someone stopping mid-slope to wait for their kid and then they lose their balance, or they’re in the lift line, or it happens while getting off the chairlift. So much of the time it’s not a great story. Even at the higher levels, if you watch the Olympics, almost everyone on the US Ski Team has had one ACL reconstructed. For sports like soccer and basketball we can quote studies saying that pre-season ACL-specific training can reduce ACL rates. But for skiing, I don’t know of any such data. I field a question like this at least twice a year from ski magazines asking “What should you do to get ready for skiing?” Just like you wouldn’t just go run the marathon, I think it’s worth doing some pre-season or pre-ski trip conditioning. Quad strengthening or general lower body strengthening is a good idea. But trying to say that that is actually going to prevent injury? No I can’t say that. One big thing I do recommend before you go out the first time every year is make sure you get your bindings adjusted.


Chondromalacia patella sounds scary to a lot of people. How do you explain it to patients? How commonly do you see it in your patients with knee pain?

I say chondromalacia patella is just a nasty word for arthritis. It can be a tiny bit or arthritis or it can be fairly severe but it’s specifically arthritis affecting the front of the knee [patella].

In my practice, it’s pretty common. There are patients who have fairly severe chondromalacia and not a lot of pain. For example, we’ll see it on an MRI but they’re actually seeing me for a meniscal repair and didn’t even know about the chondromalacia. And there are others who have just mild chondromalacia but pain every time they go up and down the stairs. Especially in women it’s a very common diagnosis, and most of the time they can get better with physical therapy.


Does the presence of chondromalacia make you concerned for their future knee health? Do you recommend they change anything because of it?

No, but, number one, I would say a lot of patients can get better even if they have significant chondromalacia, even without surgery. Number two, if they’re a runner the only thing I tell them to change is to run on flat surfaces and not hills. It doesn’t mean they can’t run a hill in a race, but it would mean that in training I don’t think it’s worth running hills. And they don’t have to avoid all squats, but essentially I tell them to beware with squats and lunges and learn how to strengthen their quads without irritating the front of their knees. That’s ideally what they’ll learn in PT.


What are some things that you’re currently researching?

Most of my research is focused on the patella. One of the problems we have when trying to do biomechanical studies looking at the affect of different types of surgeries for patellar instability or patellofemoral arthritis is that the cadaver knee we get for testing is a healthy, normal knee. But we’re not operating on normal knees; we’re operating on arthritic knees and most them are dysplastic [shaped abnormally due to arthritic changes or natural variation]. So we’ve been studying the use of 3D printed knees in biomechanical studies. One of the great things about 3D printing is that we can 3D print an “abnormal” knee and use that in our studies to look at optimizing different surgical techniques based on the shape of the knee that we actually see in the operating room. Unfortunately, we can’t 3D print replacement knee parts or cartilage yet.


What’s the latest on stem cells for knee cartilage disorders?

We were part of a multi-center trial looking at stem cell injections for arthritis because we use them in clinical practice, meaning we use them to optimize cartilage healing in the operating room and we also do stem cell injections in the office. There hasn’t been a lot of data so far. It’s amazing how commonly stem cells have been used without a lot of data. But what we know from our study is that they’re safe, meaning they aren’t making patients worse. And some patients feel substantially better. They could be useful for someone who is younger but with early arthritis who wants to remain active but is way too young for a knee replacement. We’re looking for better answers for people with arthritic pain but whose joints aren’t bad enough to warrant a replacement yet.


So as a knee surgeon you probably do a lot of knee replacements.

I do predominantly patellofemoral replacements, which is not a common operation, but a specialty of mine. Ninety percent of those patients are women. They are able to get much higher range of motion afterwards as compared to a total knee replacement and the knee feels more normal to the person. They’re able to go back to many more sports than one would with a total knee replacement. And not just because I tell them it’s okay, but because they feel like they can do it. People are back to kickboxing, competitive cycling, and certainly skiing and tennis and things that we’d let them do even with a total knee. But even though it may be safe, a lot of people with a total knee replacement just don’t feel comfortable doing higher impact sports. It feels a lot more natural when you have a partial versus a total knee replacement.

Patellofemoral replacements only replace part of the groove and the backside of the kneecap, leaving all other knee ligaments and cartilage in place.

Here’s one I hear a lot from patients: Why does a knee replacement hurt so much more than a hip replacement?

Such a good question. I think the front of the knee and the soft tissue around the patella that you have to cut through to get into the knee—the quadriceps tendon—I think is just that much more sensitive. Often people are able to tolerate pretty severe hip arthritis before they seek help. They’ll have really end-stage hip arthritis before they start to think, “whoa now this is hurting me a lot.” And on an x-ray you’ll see that there is terrible arthritis there. Whereas with knee arthritis people tend to be living with pain for much longer before they finally get a replacement.

I think there’s a lot more nerves around the front of the knee. I think you have to bend your knee through a much larger range of motion for ambulation compared to the hip. So just to walk, the knee is expected to do a lot more movement in the beginning right after surgery compared to a hip that doesn’t have to move quite as much. Also with the hip, we don’t really cut through muscles. However, even a “muscle-sparing” knee replacement procedure involves cutting muscle. It’s still pretty traumatic, it’s a lot more invasive than hip replacements.


Could it be that the synovium [joint lining] around the knee is more innervated?

I think so. There’s just a lot more nerve fibers in the front of the knee. I tell patients that even if all I did was just make the incision they would still have a lot of pain. For example, for a cartilage procedure for the trochlea the only thing I do that should hurt is the incision. Because the rest of the procedure just involves putting new cartilage in place [cartilage has no sensation], and I’m not doing anything to the sensitive bone. So the only thing that should really cause pain is the incision and yet those patients still have a fair amount of pain afterwards.


Why does the knee continue to swell long after surgery and even when we assume most of the healing is complete?

I think it depends on what’s happening in the knee. For example, with an ACL once you get over the acute inflammation your body is still turning that tendon into a ligament and that’s an active process. So, naturally, that healing and remodeling will involve some amount of inflammation. There was a study that just came out looking at rotator cuff repairs and patients who were put on Celebrex—which is a very specific anti-inflammatory—had a much lower healing rate. So I try to avoid having patients use anti-inflammatories after surgery, especially in the first six weeks. That study showed healing rates actually were substantially lower if we got rid of the inflammation. Even though inflammation is annoying it’s a part of the natural healing process. I still tell patients to control it with ice and by elevating it, but don’t get too upset about it. This is just part of what your body has to do to heal and remodel it.


It’s always nice to pick an expert’s brain when you have a chance. Hopefully you, the reader, got some good information out of this interview. To sum up:

  • Cross-training for runners is a good idea.
  • There’s no silver bullet to protect your knees while skiing, but you can’t go wrong getting strong.
  • Chondromalacia is a common finding on imaging and its severity is not very well correlated with pain. Even if you’ve got it bad, you can still be active.
  • There are some exciting breakthroughs on the horizon involving stem cells to treat knee cartilage disorders. Hopefully they really are shown to be effective (and insurance starts to cover them if so).
  • The fact that the knee is so well innervated and we ask a lot of it right after surgery may help explain why total knee replacements are quite painful early on.
  • Inflammation is natural and necessary to heal.

Thanks Dr. Strickland!

Knee pain can be debilitating if left untreated. If you’ve been dealing with something for a while and it doesn’t seem to be getting better, then let us help you find out what’s going on and what can be done. You can start just by talking to one our physical therapists here:

Arrange a 15-minute phone consult with a PT to find out how we may be able to help you!

Or click the image for some free tips about knee pain.