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KneeHab: The Total Knee Arthroplasty

April 17th, 2010

KneeHab: The Total Knee Arthroplasty

Adam P. Carson, DPT, OCS

So, you’ve been told you need a knee replacement. It doesn’t sound appealing. You’ve had that knee a long time and aren’t that crazy about parting with it. It helped you through all those football games. It helped you run that 5k. It’s been with you kneeling at church for all these years. You proposed on that knee. Heck, that knee and you shared some good times with the kids “ridin’ that horsie!”. Somehow you’ve worn that knee out. Every step hurts. Getting off of the couch is murder. Your doctor took some x-rays and said something about “bone on bone” –whatever that means. Then the fateful words “knee replacement” came out of the doctor’s mouth. That sounds about as much fun as a root canal. Well, with the right preparation and and a little hard work, a knee replacement

can make your life easier and get you back on the right (and left) track.

On occasion, a total knee arthroplasty (the total knee replacement) can come as the result of trauma, but on the whole it comes from a knee wearing out over time due to the arthritic changes of life. A professor of mine in college told me that “if you live long enough, you’ll need a new set of knees”. This isn’t that inaccurate. The far end of the thigh bone (femur) has a tissue on it called cartilage that allows some shock absorption, assists with knee motion and structure, and works similarly to ball bearings at the knee joint. The leg bone (tibia) meets the femur at the knee joint and the upper-end has it’s own set of cartilage. The kneecap (patella) makes up the last bone in the joint and works as a pulley-of-sorts helping the muscle on the front of the thigh (quadriceps) straighten the leg, climb stairs, get up from the couch, walk, etc. This cartilage wears out over time because of the pressure on top of it, not unlike a pillow or mattress. You lay on a pillow for enough years, it’s not going to be as fluffy as it used to be. Factors that make the cartilage wear out include being overweight, prior knee injuries, being knock-kneed, working on your feet on hard floors for years, and having flat feet.

The surgery itself, as wild as this sounds, is carpentry. Medical-grade saws, chisels, and files sculpt the knee joint in preparation for the endoprosthesis (the knee replacement hardware) to be inserted to the knee joint. The leg is closed up. The doctor makes sure everything bends and straightens correctly. And lots of my clients think, at this point, the hard part is over. Well, the hard part has just begun.

Physical Therapy begins the next morning. The therapist gets you out of bed, you walk with the assistance of a walker, and begin work on bending the knee. The whole goal at this point is getting the client to the point that they can safely go home. Preliminary exercises are instructed including being able to tighten the muscle on the front of the thigh (the quadriceps), lifting the whole leg, and actively bending the knee. Most people are in the hospital for 3-4 days before going home. The hospital therapy staff makes sure you have a walker, and teaches you to get around safely at the house.

At home, the second phase begins. Before you get home, make sure someone has looked (or you look before you go to the hospital) over the house to make sure pathways are clear for getting to the bed, getting to the couch, getting to the toilet, make sure there are plenty of pillows at home, and that anything you might trip over is out of the way (lamp cords, area rugs, dog toys, etc.). Depending on your doctor, you will either have home health physical therapy or you’ll be referred directly to outpatient physical therapy. It’s not uncommon for us to receive a client the day after they were discharged from the hospital. The goal at this point of rehab: get the knee straight, make sure that it can bend, and gradually strengthen the knee. Depending on the surgeon, clients usually come to physical therapy 3 times weekly initially, and then tapering down to twice a week as therapy progresses.

How much range of motion should the knee have? It varies from person to person, but a good rule of thumb is that the knee should be able to get totally straight (0 degrees) and be able to bend at least 115 degrees. At 115 degrees, a client can walk foot-over-foot going up the stairs. At our office, we push for 120 degrees mainly because once therapy stops, the clients tend to lose a few degrees of bend. This way if you lose 5 degrees, the minimum 115 degrees is still present. The clients focus on how much bend they have. Yes, that is important, however, but getting the knee to 0 degrees and maintaining that is of utmost importance. If the knee does not get straight, the client ends up with a limp, and the life expectancy of the knee replacement is shortened.

The muscles around the knee do one of two things: they get weak or they get tight. The quadriceps weakens because of swelling and trauma. This is that particular muscle’s response to injury. The hamstring, the muscle on the back of the thigh, and the calf muscle each tighten in response to trauma and surgery. The physical therapy program that you undertake after surgery will be designed to strengthen the quadriceps, and stretch the hamstring and calf musculature.

Many of the exercises you perform will have three functions: strengthening the knee, increasing the knee’s range of motion, and balance. Your exercises will be open-chain (non-weight bearing) and closed-chain (weight bearing). The therapist will have you use a leg press, use a stationary bike, step up and down on a short-step, they might have you “drive” an office chair around backwards, stretch your muscles, lay on your stomach and stretch out the leg, lay on your back with your foot on wall and slide that foot up and down the wall causing that knee to bend. The exercises sometimes seem crazy but they all have a purpose: get that knee working and get you moving again! Another form of exercise you will probably do is practice standing on one leg: your balance will be messed up after surgery. Recovery of balance is essential to your knee replacement recovery.

Once most of your therapy goals have been met, usually 6-8 weeks, physical therapy will release you to a home exercise program. Keeping up with the home program is essential. The knee continues to heal over the course of a year. Swelling will continue, albeit lessening so, over that year.

How long does a knee replacement last? That varies from person to person. It should last you 15-20 years. How do you maintain it? How do you make it last longer?
Lose weight. The less weight pushing down on it, the less wear-and-tear on the new knee.
Wear good shoes and arch supports. The more shock-absorption that occurs in the feet, the less force that is translated to the knee.
Avoid kneeling on that knee.

Finally, how can all of this go easier? Can you get ready for the surgery? YES! If you know that a knee replacement is in your future, talk to your doctor about “prehab”. Go see a physical therapist to get an exercise program in place that will assist in getting the knee ready for the surgery. The stronger the knee is before surgery, and the better the knee bends and straightens before surgery, the easier the recovery afterward (not necessarily quicker). Start wearing arch supports in your shoes (off the shelf arch supports are fine). Start losing weight.

Recovery from knee replacement isn’t easy. The harder you work on it, the more reward you’ll get from it. It will teach you patience. Truthfully, knee replacements are a growing experience. There is a brotherhood and sisterhood among those that have the procedure. It’s not uncommon for clients at the clinic to pull up their pant leg and compare scars and tell war stories. Don’t be discouraged! You’ll get back on the right path and get back to your life. Who knows, you might want to get the other one done someday.

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