In this article, I am going to show you how to improve your knee extension and flexion range of motion after an injury or surgery!
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Knee Extension Range of Motion
Normal knee extension is typically 0°, meaning the knee is completely straight. In some cases, the knee may extend slightly beyond this into hyperextension.
Whether you’re recovering from an injury or surgery, the goal is typically to restore your knee extension to the same amount as your uninvolved side. This means if you can achieve 5° of hyperextension on your uninvolved side, then your goal is to regain 5° of hyperextension on your involved side. You’re aiming for symmetry.
If you’ve had surgery on both sides or your uninvolved side isn’t a good reference due to a prior injury, then I would recommend, at the very least, aiming to get the knee completely straight.
Restoring your knee extension as quickly as possible is a primary goal following most knee injuries and surgeries because getting your knee straight sooner makes walking and other activities easier. I’ll review two main options that will improve your knee extension, as well as reduce swelling and improve your function. These exercises are usually introduced within the first few days after an injury or surgery.
The easiest thing you should be doing throughout the day, every day, are quad sets. Straighten your leg as best as you can, then squeeze your quads (the muscles on the front of your thigh) by trying to push the back of your knee into the floor or surface you’re resting on. Hold for 10 seconds, relax, and repeat 10 times.
If your knee has limited extension after surgery, you can place a small towel under your knee for comfort. To progress the quad set, prop your heel on a towel or small object in order to move through more range of motion.
You can also do quad sets from a seated position. If you are sitting in a chair, on the couch, or on your bed, scoot forward to the edge, and straighten your leg as best as you can. From here, squeeze your quads for 10 seconds, relax, and repeat 10 times.
If you’d like to intensify the movement as your range of motion improves, you can use a strap to pull up on your foot, adding a calf and hamstring stretch while you perform the same quad contraction.
You should start these quad sets early and perform them as often as possible – multiple times throughout the day, every day. These are essential for restoring knee extension, reducing swelling, and improving function, which, again, will make walking and other activities easier. It’s hard to overdo these, so I can’t stress enough how important they are.
Another exercise most individuals will want to do, especially after surgery, involves propping your heel on a towel or object, trying to accumulate about 30-60 minutes a day.
Since some people might not tolerate this duration initially, it’s okay to break this up into 5-15 minute sessions, 2-6 times a day. Some individuals may even need more or less time depending on their injury, surgery, personal circumstances, or their physical therapist’s recommendations.
Over time, you can progress by increasing the frequency and duration, or by adding weight to increase the stretch, such as placing a small weight on your thigh or a bag over your leg.
As you gain more strength and control, here are 3 additional exercise options:
Option 1: Straight Leg Raise. Lie on your back with one knee bent, straighten the other by squeezing your quads, and lift until your thighs are in line with one another. Slowly control back down. An important milestone is being able to perform this movement with your knee completely straight. Once you can do that, build up to 3 sets of 10-20 repetitions.
Option 2: Banded TKE. Grab a moderate to heavy resistance band, securely anchor it to a sturdy object in front of you, and place the other end behind your knee. Push the back of your knee into the band by squeezing your quads, hold for 10 seconds, relax, and repeat 10 times. If you don’t have a band, you can also perform a similar movement by pushing the back of your knee into a towel, small ball, or another soft object against a wall.
Option 3: Retro (or Backward) Walking. Take a small step back, slowly lower your heel to the ground, and straighten your knee by squeezing your quads. This can be done in open space or on a treadmill for 5-15 minutes at a time.
I’ll discuss programming a bit later in this article, so for now let’s move on to exercises for improving knee flexion range of motion.
Knee Flexion Range of Motion
Normal knee flexion is typically around 135° or getting your heel to your butt, or very close to it.
In most cases, your goal is to restore the same amount of knee flexion as your uninvolved side, if feasible. For instance, after an ACL reconstruction, meniscus repair, or mild ligament sprain, this is a reasonable goal. In contrast, following a total knee replacement, achieving 135° of knee flexion may not be realistic or even necessary. To give you some context, many post-surgical protocols recommend restoring about 115-120° of flexion by 2-3 months after surgery.
I’m going to review 7 options of varying levels of difficulty. If you don’t have restrictions, these can usually begin within the first few days after an injury or surgery.
However, keep in mind that certain surgeries will have restrictions for a set duration of time to protect the surgically addressed structures. For example, after a meniscus repair, your surgeon may restrict knee flexion to no more than 90° for a month or longer.
Option 1: Heel Slides. The first (and probably most popular) option is heel slides. While lying on your back, slide your heel toward your butt, bending your knee as much as you can. Hold the end position a few seconds, then slowly straighten your knee, and repeat. You can place your foot on a slider if you’re on carpet, a towel if you’re on a hard surface, or simply hover your heel just above the ground.
To increase the intensity, wrap a towel or strap around your foot, slowly slide your heel toward your butt, and then gently pull on the towel or strap to help bend your knee further. These heel slides can be performed for 2-3 sets of 10-20 repetitions.
Option 2: Recumbent Bike. Position the seat further back and begin with partial revolutions, moving your knee in and out of as much flexion as tolerable. Once you’re able to complete full revolutions, gradually move the seat forward to expose the knee to more flexion.
You can also follow a similar progression on a stationary bike. Start with the seat at a higher level and do partial revolutions. As your mobility improves and you can complete full revolutions, move the seat down to further challenge and increase your knee flexion.
This can be done daily for 5-30 minutes, gradually increasing the duration as tolerated. Early on, you may only manage 5 minutes a day, but as your tolerance improves, you can slowly work up to 20 minutes or more.
Option 3: Scooting Knee Flexion. Sit in a chair with your foot flat on the ground, then use your arms to scoot your hips forward, which will help bend your knee further. Perform for 2-3 sets of 30-60 second holds.
Option 4: Seated Heel Slides. Sit on the edge of a chair and place your foot on a slider if you’re on carpet or a towel if you’re on a hard surface. Gently slide your foot backward, trying to bend your knee as much as you can. You can use your other leg to provide gentle overpressure if desired. Hold the end position for a few seconds, then return to the starting position. Repeat for 2-3 sets of 10-20 repetitions.
The next two options involve a component of kneeling, which might not be comfortable or realistic for everyone, especially soon after surgery when the wound is healing and is more sensitive to pressure.
The first kneeling option is a kneeling progression. Start on your hands and knees and gently rock your butt back toward your heels as far as comfortable. To progress, perform a tall kneeling rock back, where you transition from a tall kneeling to a low kneeling position. Finally, if you want to bias one knee, start in a half kneeling position and sit your butt back to your heel. Hold the end position for a few seconds and repeat for 2-3 sets of 10-20 repetitions.
For any level, you can place a small towel behind your knee which may make the bottom position more comfortable and allow you to move into more knee flexion.
The second kneeling option is called a couch stretch. Set up in a half kneeling position with your back foot resting on a bench, chair, or couch. Gently rock backward, trying to bring your butt toward your heel. Aim for 2-3 sets of 30-60 second holds or 10-15 repetitions, moving slowly in and out of your end range.
The last exercise option is squats, which everyone will incorporate at some point in their recovery to improve range of motion, strength, and tolerance to weight-bearing knee flexion.
Depending on your injury or surgery, you will likely start with mini squats and progress to regular squats over time.
Some individuals might even work their way up to heel elevated squats. By elevating your heels on plates, wedges, or another object, you’re able to squat even lower, especially if you build up to holding a weight in your hands. Aim for 2-3 sets of 5-15 slow and controlled repetitions.
Knee Range of Motion Exercise Recommendations
Before I discuss programming, I have two important recommendations:
First, while regaining range of motion may feel uncomfortable at times, it should never be unbearable. If you’re gritting your teeth or holding back tears during the exercises, it can be counterproductive, as the resulting pain and swelling can delay your progress.
This leads to the second recommendation: closely monitor and manage your symptoms. In the early days and weeks after a knee injury or surgery, it’s crucial to find the right balance of exercise, activity, and movement that will improve your symptoms and function without overdoing it. For example, you might want to rush off your assistive device as quickly as possible, but crutches, walkers, and canes are meant to help offload the knee temporarily. Discontinuing an assistive device before you’re ready can also be counterproductive.
Restoring your range of motion is going to be a lot easier if your pain and swelling are managed appropriately. Along with the recommendations just mentioned, other options for managing symptoms include compression, ice, and elevation, if desired.
Programming Knee Range of Motion Exercises
So, how do you put all of this information together to create a structured program?
Well, your exercise selection and rate of progression will vary based on numerous factors including your injury or surgery, function, tolerance, symptoms, access to equipment, and goals. I will show you 4 examples to illustrate what I mean, but keep in mind that your unique circumstances should be discussed with your surgeon and physical therapist.
1. You are recovering from an ACL reconstruction.
In this case, exercises can usually be started in the first few days after surgery. To help restore knee extension, the heel prop exercise can be performed for 5-15 minutes, 2-6 times a day while the quad sets should be done as often as possible every single day. For knee flexion, you might ride a stationary bike for 5-10 minutes every day and perform the assisted heel slides for 2-3 sets of 10-20 repetitions, 2-3 times a day.
As your range of motion, symptoms, and tolerance improves, you can progress the volume and intensity of exercises. For instance, you might add a weight to the heel prop exercise and increase hold times to 10-15 minutes, start performing straight leg raises, and ride the bike for longer durations, all while continuing with the assisted heel slides until full knee flexion is achieved. You’ll likely be doing other exercises relevant to ACL rehab as well.
Your goal is to restore the same amount of knee extension and flexion as your uninvolved side (assuming it’s feasible) as soon as possible. Typically, regaining your knee extension will take a few weeks, while restoring full knee flexion may take about 2-3 months or longer.
2. You recently had your meniscus repaired.
Your programming will eventually look very similar to the previous example, but there is one major difference – your surgeon may place a restriction that prevents you from bending your knee past 90° for a month or more. This means that until your restrictions are lifted, you may be limited in your exercise selection and range of motion.
3. You had a total knee replacement.
Again, your programming may look similar to the ACL example, however your timeline, expectations, and end goals might differ. For instance, while your goal is to restore full knee extension, it’s important to understand that achieving full knee flexion may not be realistic or even necessary. There are some surgical protocols that recommend reaching about 115-120° by 8-12 weeks, but this may not be the case for everyone.
4. You experienced a minor knee injury a few days ago while practicing jiu jitsu.
If you notice knee swelling, active exercises like the heel slides and supine quad sets can be used early on to reduce your swelling and regain your range of motion. Over the next couple of weeks, you might decide to perform banded TKEs to improve knee extension strength and control, while also working on kneeling and deep squats to build tolerance to end-range knee flexion and better prepare for your return to sport.
Exercises like the heel props don’t necessarily need to be included since your range of motion will likely improve as your swelling goes down and your tolerance improves.
Summary
Here are the 3 main takeaways I want you to know about restoring your knee range of motion after an injury or surgery.
1. Keep exercises tolerable, try to minimize flare-ups and increases in swelling, and follow the post-operative restrictions and recommendations from your surgeon and physical therapist.
2. In most cases, your goal is to restore the same amount of knee extension and flexion as your uninvolved side.
3. Perform these exercises early and often within tolerance. The sample programs I provided might seem like a lot, but regaining your knee range of motion is extremely important for improving symptoms, restoring function, and ensuring the rest of rehab goes smoothly.
If your range of motion remains restricted after a certain period of time, it may be recommended to follow up with your surgeon. For example, someone struggling to regain at least 0° of knee extension by 4-6 weeks after an ACL reconstruction may need further evaluation.
Lastly, for those who are planning to have surgery, the exercises reviewed in this article can be used to help prepare you for both the procedure and the post-operative rehabilitation process.
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