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The knee joint is a hinge-type synovial joint, which allows for flexion and extension and a small degree of medial and lateral rotation. Extension of the leg, which is produced primarily by the quadriceps femoris (4 muscles located in front of the thigh) and connect the femur with the tibia, will be the subject of this article.
Most people are concerned with their ability to bend the knee (flexion) after surgery but it is just as important to gain full extension after surgery (ability to straighten the leg). Terminal knee extension is achieved when the angle of your leg is zero degrees when extended straight.
I will discuss reasons why some patients have less leg extension after knee replacement surgery and share a few exercises I was prescribed to increase my knee extension.
Why Care About Knee Extension
- Because the body may not work the way we want it to. This means we might not walk correctly and our body will be slightly out of balance (read about my experience walking two weeks after knee replacement).
- Because when one part of our body isn’t working right, other parts of our body compensate to help out and can risk injury.
- Because poor extension can result a fall or accident.
Reasons Why You Have Less Extension After Knee Surgery
You may have lost total extension in your knee prior to TKR.
The weakness of the quadriceps muscles can be due to less activity before TKR. You may have been in too much pain to exercise the muscles around your knee and that could cause significant muscle atrophy.
You can give your rehabilitation a big boost if you are able to strengthen the muscles in your leg prior to your TKR. Likewise, it is important to start strength training in your quadriceps as soon as possible after TKR.
Less than full extension can cause you to have an abnormal walking pattern. Limited knee extension will also affect other joints (especially the hip and ankle).
It also also limits the ability of the quadriceps muscles to function properly. Within 7 to 10 days after TKR, many people can get the knee entirely straight (full extension).
After TKR there is pain and swelling that can make it hard to exercise and difficult to achieve full extension. Swelling and pain after TKR are normal and may inhibit your range of motion somewhat, especially the first few days following your surgery (read about my range of motion after surgery).
The fluid and swelling will diminish as you apply ice, elevate, rest and exercise. As the swelling decreases you will find it easier to exercise and improve range of motion. Put don’t put your rehab off.
Be ready to start physical therapy on day one post surgery.
There is going to be pain and it is easy to give up and not follow your physical therapist’s plan, especially when they are not present. It’s going to be tough but the times when you are exercising without supervision and encouragement are the times that you need to really tough it out and stick to the program.
You may have not had total extension in your leg before TKR. Loss of extension may be the result of injury or prior knee surgery.
The loss of extension often occurs because the hamstrings in the back of your leg contract and the inactivity of the quadriceps causes them to become weak.
Just like your muscles, the ligaments and tendons around your knee may not be used to full extension. Through therapy and exercise they too will slowly strengthen and help with your extension, support and stability.
Knee surgery doesn’t guarantee “full” extension. Some surgeons and therapists may be content for you to come within a few degrees of zero.
Your health history, age and range of motion before surgery may be deciding factors. If you do experience a stiff knee after TKR you may need a more aggressive physical therapy plan to help with extension.
A manipulating procedure under anesthesia with no incision is another alternative. Your surgeon forcibly moves the knee to break up scar tissue that will improve your extension (learn how I massaged the scar after surgery).
Malpositioning of the implant can cause imbalance, but with specific tailor made knees today, the risk of malpositioning the implant is extremely low. Surgeons make an effort to balance the knee at the time of TKR.
This assumes that the knee is not too tight or not too loose so that it balances when the knee is both straight and when bent.
My Knee Extension After Surgery
My doctors and therapists told me to expect post surgery range of motion to be similar to my pre-surgery range of motion. I was able to reach full extension a few days after my surgery.
The flexion was the real challenge for me. My therapist included extension exercises along with my range of motion exercises.
I will share 3 extension exercises that I did to increase knee extension after surgery.
- Using a rolled towel that you can tape or a foam roll place it under your ankle while you lay flat on your back on a firm bed. Using gravity and some force of your own , flex and push down on the towel. Do 20 reps holding for 5 seconds each. Place the towel or roll under your knee and lift your foot up and hold, 20 reps for 5 seconds each.
- While watching TV or reading sit in a comfortable chair. Extend your leg so that your ankle rests on a footstool or coffee table allowing gravity to pull the knee joint down (straight). Do this as long as you can endure the uncomfortable feeling, then rest before continuing.
- Toe, ankle, and leg raises. I used the kitchen counter to balance. I did 30 toe raises with both feet and held them for a 4 second count. I then put my good foot behind my surgical calf and did 30 more 4 second count toe raises with my surgical knee. I did the same with the other leg. Next I balanced on my ankles and raised my toes 30 times for a 4 second count. Then I switched to one ankle at a time. Finally I balanced on one leg and keeping my leg straight I lifted my right leg to the right as high as I could 20 times. I then did the same with the left leg
I repeated all of the above for all of my 3 daily home therapy sessions.
While exercising it is okay to experience some paints as long as you can tolerate it.
Try doing extension exercises on a firm couch or recliner during TV commercial breaks or at the end of a book chapter.
After your incision heals try sleeping on your stomach with your legs straight and your toes off the mattress.
Regaining normal knee range of motion including full knee extension after TKR is critical for proper mechanics when walking, and returning to activities and sports.
The first few weeks are the most important for improving extension and flexion. Do your best to tolerate the pain and be diligent with your therapy.
If you have questions about your progress consult your physical therapist or surgeon.