Your knees and hips are your largest joints. They support your body weight and work in close coordination so that you can run for the bus, squat to lift a child, or play hoops.
Over time, many of us experience knee or hip pain, and physical therapy, pain-relief medication, minor surgery, or some combination of these provides relief. But for some, knee and hip problems become so intractable that a knee or hip replacement offers the best chance for a return to pain-free mobility.
Dr. Donald T. Reilly is an orthopedic surgeon at New England Baptist Hospital and a long-time member of the Harvard Health Letter's editorial board. He recently answered some questions about joint pain and replacement for Harvard Health Publishing' readers.
Which is easier to perform, a hip or knee replacement?
A hip replacement. An experienced surgeon could probably do a hip replacement blindfolded because you can feel everything, and components of the replacement are put right into the bones. But a knee replacement involves releasing ligaments, putting the components onto bone — and then getting things to balance out just right. The ligaments can be damaged or shortened by arthritis, so you really have to make sure the knee is stable. And the joint must flex and rotate.
And how about the results for patients?
A hip replacement is a much less painful operation. People are on crutches for a while, and then their hips feel normal. But it takes six months to a year to recover from total knee surgery, and even then, the knee just doesn't feel normal.
Why the difference?
The hip is really a much simpler joint. The knee has to balance off-center loads and move side to side. And with a total knee replacement, you are removing a lot of tissue and bone. Postoperative pain is higher with knees since the soft tissue affected by the surgery must stretch more than soft tissue around the hip.
So knee patients have to accept some limitations?
Running and jumping are out. What I say to my patients, in a joking fashion, is that the only time you are going to run is if a bus is going to hit you.
Aren't there partial knee replacements that involve only one side of the knee?
Yes, and they are easier to recover from. It is the perfect operation for the 85-year-old who only has a problem in one portion of his or her knee and minimal deformity. The worst candidates for partial knee replacements are the people who often get them — young athletic people. They recover fast. They feel normal. And then they end up loosening their partial replacement in no time.
How about less drastic fixes for knees?
I don't have much experience with Synvisc and the other viscosupplementation injections into the knee. I am sure they work reasonably well for some people, but you can't expect good results if you have severe arthritis, with bone rubbing on bone. Tears in meniscal cartilage can be trimmed, but that is for mechanical symptoms of buckling, not real arthritic pain. As for microfracture — putting very tiny fractures in bone to induce the growth of cartilage — the results have been very, very spotty.
And, yes, good physical therapy can help if the muscles around the joint are in good shape — but it's tough to get them in good shape, because the joint hurts.
And cartilage implants?
Well, it seems like you should be able to grow cartilage. But cartilage has no blood supply, so it doesn't heal from injury. And the mechanics of it, the way it is built — it's a very complex material. So far, artificial cartilage hasn't worked.
How many knee and hip replacements have you done?
In my career, several thousand.
So does practice make perfect? Surgical volume is supposed to mean better outcomes, right?
I think that's definitely true. The complication rate is lower. When you do it over and over, you have seen it all, so to speak. And that's even more the case when it comes to the hospital and the nursing staff and postoperative care, which are so critical to good outcomes.
Hip and knee replacement involve a lot of sawing and drilling, don't they?
Yes, they are real insults to the human body. But, like anything else, you can't exceed limits. You are working in a window where you don't want to do too much, but you don't want to do too little, either.
I had a patient a while back who did marquetry — elaborate wood inlay — gorgeous stuff. He said, "You guys must have fabulous tools." I told him no, they are primitive compared to what you have. When a piece leaves your shop, it's as good as it is going to be. But in my patients, I have something called healing, so after they leave my shop, there's improvement. In orthopedic surgery, the surgery starts the process. Healing finishes it.
Does experience working with tools help doctors going into orthopedic surgery?
I think it does. In fact, men used to have a real advantage because they grew up using tools. But that's not so true anymore. Women have started using tools more, and men are using them less, so it's now pretty even.
What can people do to avoid needing your services?
Stay active, keep your muscles strong, don't get obese, have good genes.
How about you — any chance you're headed for a hip or knee replacement?
My back may be an issue, but I think my knees and hips will be all right. My mother is 94 and she still walks a mile and a half two or three times a week.
So you think you are genetically gifted with good hips and knees?
Yes, that's the main reason. And I haven't had any serious injuries to my hips or knees.
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