Episode 301 | Audit Your Knee Flexion: A Simple Assessment for ACL Rehab

What is up team and welcome back to another episode on the ACL Athlete Podcast. I have a quick question for you. Can you get your knee fully bent? Can you get your heel to your butt? The answer is going to depend on where you are in the process, especially if you are early in recovery or still trying to get that range of motion back.

This is something I want to talk through today because we see many people who think they have fully restored their knee flexion, but when we assess it, there is still a gap. That is what this episode is all about: knee flexion after an ACL injury or surgery, how far it needs to go, how much you should care about it, when to prioritize it, and how to test it yourself today. You can literally do this with a strap and your phone. You do not even need a strap for one of the assessments. I will also explain what to do when the test tells you something you did not expect, along with the thing I see people do most often to chase flexion and why I want you to do much less of it.

If you have heard Episode 297, where we discussed auditing your knee extension, think of this as its partner. The general principles are similar, but there are some differences in how we approach each. Flexion is typically more forgiving in some ways, but it can also be more deceptive. I want to cover those nuances, especially when it comes to priority and timing.

Let us start with where flexion sits on the priority list because I see many people putting it higher than it needs to be. Early on, the goal is a quiet knee. After an injury or surgery, getting the knee quiet is one of our primary objectives. If you are unfamiliar with what a quiet knee means, you can search the podcast for that phrase. I discuss it in detail in other episodes, including the different components of range of motion.

Range of motion is part of having a quiet knee. Within that category, extension is priority number one, and flexion, or bending your knee, is number two. Flexion matters, and we are going to gradually move it forward, but we are not sprinting toward it the way we do with extension. This is where I see many people fall into a trap, especially early after surgery when nobody has clearly communicated these priorities.

A lot of people have never heard of the quiet knee concept. They simply know they need to do their exercises. They show up to physical therapy and perform the usual quad sets, straight leg raises, heel slides, hip abduction and adduction, and side-lying lifts. These are the classic exercises in a post-operative ACL home program. We may use some of them, but we do not necessarily spend a lot of time on them before moving forward.

What is often missing is a clear target. People are not told exactly what they are working toward or the general time frame in which they should aim to restore it. Having those benchmarks gives you something to assess instead of relying solely on two or three physical therapy sessions a week and hoping everything stays on track.

The trap is that flexion is the more gratifying one of the two. Normal knee flexion for most people is around 140 to 145 degrees, so you can see progress constantly as you work toward that range. After an injury or surgery, your knee is usually positioned close to extension, somewhere around zero-ish degrees. You may be wearing a brace, or you may not have one, but your leg is generally close to straight.

With extension, you are fighting for a much smaller amount of range of motion, perhaps 10 to 15 degrees in total. It can feel small and boring, and people often assume they have it because their leg looks straight enough. However, they may not understand the difference between simply having a straight-looking leg and achieving true knee extension with a solid heel pop and quad set. That distinction is important.

Because bending the knee involves a much larger range of motion, people tend to pour more time into it. They may also feel hesitant to bend their knee initially after surgery or injury, so they put more attention into that movement. Meanwhile, they quietly assume the straightening part will take care of itself.

I am not saying to pick one over the other. I am saying to have a priority list and understand how much emphasis each one deserves. If your extension is clearly behind the other side, most of your range-of-motion effort should go there. You will still work on flexion, touch it regularly, and continue to make progress. But if we were to put these priorities on a scale, it would not be a 50/50 split. Extension would receive more attention.

Our goal is to get your extension matching the other side, including hyperextension, except for people who are incredibly hypermobile and have something like 15 or 20 degrees of hyperextension. For the vast majority of people without unusual range-of-motion differences, we want that extension to match the uninvolved side.

Once your extension matches the other side, including hyperextension, you can continue checking it to make sure it stays there. Look at your heel pop. Make sure your toes rise to the same height, your heel comes off the ground, and your quad contraction feels solid and locked in. Keep auditing that regularly, especially early in the process, but even later on. As your extension gets into a good position, flexion can receive more of your attention.

Again, you are not choosing one or the other. You are simply tipping the scale toward extension when it is behind. Flexion is still part of your daily work, but its progression is generally more gradual. If you have not checked your extension against the other side yet, start there and listen to Episode 297 to learn how to audit it.

Another important consideration is that your surgery sets the rules. If you are in a brace, have a restriction limiting you to 90 degrees, or have a meniscus repair with a bending restriction, that restriction is your ceiling at that point in recovery. You may need to unlock your brace to perform certain movements, but you should follow the specific instructions you have been given.

Some meniscus repairs come with range-of-motion restrictions depending on the surgeon’s preferences, the area of the meniscus that was affected, and the type of repair performed. You may be limited to 60 degrees or 90 degrees, or your range may gradually be increased each week. Everyone has different rules, and we have to respect them. We work with what the joint allows and within the restrictions of the procedure. If your limit is 90 degrees, then 90 degrees is where you work. You do not push beyond that without appropriate clearance.

You might be wondering why we need to care about flexion at all, especially if extension is the higher priority. The answer is that knee bending is important for your everyday function. You need it when walking, sitting in a chair, using stairs, and even getting on a stationary bike.

Without enough knee flexion, your body will find ways to work around the limitation. You may compensate without even realizing it. I see this when people start walking. Instead of bringing the leg through a normal gait cycle, they circumduct, swinging the foot around to get the leg forward because they cannot comfortably move through the amount of knee flexion they need.

These compensations can happen in different parts of your daily life. That is why we want to restore flexion gradually. It is a basic part of normal function, and it matters beyond just getting through your daily activities.

The bigger problem is that people often think they have full flexion when nobody has properly checked it. Maybe it was an important priority early in recovery, and they reached 120 or 130 degrees. But after that, there was no intentional work to restore the remaining range. It was assumed that the rest would come back with time.

A few months later, they have only recovered 80 or 90 percent of their range of motion. They assume it is fully there because they can do most of their daily activities without noticing a limitation. We see this often when people come to work with us later in the process and tell us they have full knee flexion.

Flexion can be more deceptive than extension because you may not regularly challenge the very end range. Unless you are someone who performs deep squats, practices yoga, or frequently gets down on the floor with your kids, you may not notice the limitation. Yoga, for example, can expose it because you need to sit back on your heels.

If you recover 80 percent of your flexion, you may not feel particularly limited in everyday life. But restoring the remaining range is still important for normal joint movement, joint stress, and your specific goals. It can affect activities such as sitting back on your heels, yoga, and squatting.

People also tend to shift their weight toward the uninvolved side when they do not have full flexion. Sprinting is another area where this limitation can have a significant impact. During a full sprinting cycle, your knee goes through substantial flexion. If you look at an elite sprinter, you will see the heel come close to the butt as the leg cycles through.

If you do not have that range, you may whip the leg around, rely more heavily on the other side, or limit your movement. This can affect your sprinting mechanics. I see hamstring strains in this context, particularly when people do not have the necessary range and control. There can be a trickle-down effect on athletic performance, gym-based activities, and everyday function.

What is the target? It is your other knee, not an arbitrary number on a chart. We use the uninvolved side as the baseline. Of course, this becomes more complicated when someone has injured both knees at different times and never fully restored the first one. We have people on our roster in that situation, where we are working on one knee while the other knee is also not a reliable reference.

However, after assessing enough knees, you begin to understand what normal movement and end range should look and feel like. We use that clinical understanding alongside the other side as our reference.

Here is what normal knee flexion should look like. Lie on your back and bring your heel toward your butt until your calf meets the back of your thigh. When those muscle bellies meet, the end feel should be soft and bouncy. It should feel like your calf and hamstring are coming together, similar to what happens when you bend your elbow and your forearm meets your biceps.

It should not feel like you are hitting a hard wall inside the joint. If you feel that kind of wall, it is something to notice and take note of because it may indicate a different issue.

There is one important distinction when assessing this movement. If you lie on your stomach or stand and pull your heel toward your butt, your quadriceps are being stretched because your hip is extended. You may run out of range for a reason that is not necessarily coming from the knee joint itself. It could be tension in the quadriceps muscle.

Some people notice this more than others, particularly those who have had a quadriceps tendon graft or generally have tighter muscles. They may feel the limitation in their quadriceps or hip flexors as they bring the heel toward the butt while standing.

When you are lying on your back, your hip is flexed, which reduces the stretch on the quadriceps. This allows you to isolate knee flexion a little more and assess the knee joint without the quadriceps being as much of a limiting factor. There is value in assessing both positions, but we want to understand whether the limitation is actually coming from the knee or from the tension created by the position of your hip.

People often ask for numbers, so here is a general ballpark. These targets are based on research, data we have collected, and useful clinical benchmarks. They are not rigid rules. Your surgery, graft type, repairs, and other individual factors can influence your progression.

Assuming there are no restrictions, we would like to see your flexion moving toward 90 degrees by around two weeks and 120 degrees by around four weeks. These are broad targets for several reasons. If you are not hitting them, that does not mean you are behind or doomed. Plenty of people progress more slowly, while others reach these targets sooner.

What matters most is steady, gradual progress. We need to look at your subjective symptoms, objective measurements, and the trend over time. How does the knee feel from day to day? What does the range of motion look like? Is it improving week after week and month after month? That overall picture is much more important than whether you hit an exact number on a specific date.

We use 90 degrees by two weeks and 120 degrees by four weeks as general benchmarks. Once you reach 120 degrees, the urgency to push flexion decreases. At that point, you can perform most of your rehabilitation, training, and daily activities without as much compensation. From there, people typically continue gaining range gradually.

We are not trying to jam the knee into a full bend as quickly as possible. Some people want to go all out and force the range, so we have to be intentional about educating them. That is not the goal with flexion. Extension is different. We want to restore full extension as soon as possible, but flexion is a more gradual process.

This brings us to the idea of microdosing. Rather than doing one long session of range-of-motion work, spread your work across your waking hours. You might perform five to eight short sessions of five to ten minutes each. Every session is also an opportunity to check in with your knee.

How did the knee feel before the session? Did it flare up after your last workout or range-of-motion session? Have you spent a long time on your feet? Did you have a particularly demanding day? All of these factors can influence how much work your knee can tolerate at that moment.

Adjust the next session based on the feedback you receive. If the knee feels good, you may nudge it a little further than the previous time. You are not trying to win the entire process in one session. The goal is to create a compounding effect through frequent, small doses of movement.

You are giving the knee a steady stream of small requests and allowing its response to guide your next step. Should you push a little further, or should you back off? Maybe you planned to do ten minutes of range-of-motion work, but you have already spent the last hour standing in a meeting and your knee is bothering you. In that situation, you may need to reduce the session and let things settle.

This can be difficult if you grew up with a no-pain, no-gain mindset. It is especially challenging for competitive, type-A people who are used to working hard and pushing through discomfort. I understand the mentality of embracing the suck, particularly if you have a sports background. But in the early weeks of ACL rehabilitation, that approach can backfire.

In many cases, no pain, no gain does not apply well to managing a surgical rehabilitation process or a chronic injury. That is a very different context from working to improve your fitness, physical capacity, or sports skills when you are not injured. When you push too hard, the knee can flare up. You may lose a day or two, sometimes longer, because you have entered a cycle of irritation and increased symptoms. You can end up further behind than you would have been if you had performed smaller, steady sessions and adjusted based on the feedback from your knee.

Now let us get into the actual assessment. You will need a strap, belt, or towel, a floor, and your phone. The whole process should take around five to ten minutes.

First, remember that this is a test, not a stretch. You are collecting information. If you force your knee into a bigger range just to get a better number, that number does not mean anything. You may also flare up the knee, which is not worth it. If your surgeon has restricted how far you can bend your knee or whether you can kneel, follow those restrictions and skip anything you have not been cleared to do.

You also need to consider donor-site discomfort. If you had a patellar tendon graft, for example, or you have discomfort at the front of your knee, that may influence how you approach the assessment.

Test one is the passive heel slide. Lie on your back and loop the strap around your foot. Use the strap to bring your heel toward your butt. Let the strap do the work rather than actively bending the knee yourself.

Notice three things: How far does the heel go? What stops it? And does the knee have a soft, bouncy end feel, or does it feel like you are running into a wall or experiencing tightness inside the joint? Take note of what you feel, then perform the same assessment on the other leg so you have a reference.

Test two is the active heel slide. Stay in the same position, but remove the strap. This time, slide your heel toward your butt using your own hamstrings. Notice where the heel stops, whether it matches the other side, and whether you experience the same symptoms or something different.

The passive assessment tells us what range the joint can access or allow at that moment. The active assessment tells us what you can actually control with your muscles, particularly your hamstrings.

Test three is the tall kneeling rock back. This is the assessment that I would say gives us the most information and insight. Get on both knees and sit tall. Ideally, position your phone behind you so you can record the movement.

Slowly rock your butt back toward your heels. Try not to use your hands, although it is fine to use them for support if you need to. You can place your hands on the floor, a chair, or another surface in front of you while you are still working through the movement. Eventually, though, we want you to be able to perform it without relying on your hands.

Watch the video and ask yourself four questions. Does your butt reach your heels? Does your hip or pelvis stay level, or does it shift? Is your weight distributed evenly between both sides? And how does each knee feel compared with the other?

A common compensation is for the involved side to unload slightly. As you rock backward, your butt may rise a little on that side, while your pelvis shifts and leans toward the uninvolved leg. You might not even notice that you are taking weight off the involved knee.

Pay close attention to the pelvis. Does it stay level, or does it shift? Is the pressure even through both knees, or are you quietly moving away from the involved side? Also notice whether you feel more pressure or discomfort at the front of the involved knee. Can you sit back and relax, or does the position feel noticeably different from the other side?

If you can sit all the way back, with no gap, no pelvic shift, no weight transfer toward the uninvolved side, and the same feeling in both knees, that is a great sign. That is what we are looking for when we assess full knee flexion.

So why do so many people think they have their flexion back when they do not? There are two common reasons. First, they can get their butt to their heels, so they assume they are done. But look at how much work it takes compared with the other side. If one knee moves effortlessly and the other requires effort, force, or a lot of strategy, those knees are not functioning the same way yet.

Second, the compensation can be almost invisible from your own point of view. You rock backward, quietly unload the involved side, and shift your pelvis a little. It feels like you have reached the same position, but the video shows something different. You will not necessarily see this from the front, which is why I want you to film the movement from behind.

I have seen people come in thinking their flexion was fully restored, but the reasons for the limitation vary. Sometimes their approach to rehabilitation was not appropriate. Sometimes swelling remained high. When we change the strategy, range of motion can improve significantly. That is a clinical observation, and it is one of the reasons I want you to assess your movement instead of assuming everything is back.

Other people make enough progress early on that flexion moves to the back burner. They reach a point where it does not limit most of their daily activities, so they continue with the rest of rehabilitation without ever having the end range properly assessed again. They may eventually graduate from physical therapy or run out of insurance visits with 80 or 90 percent of their flexion restored, but not all of it.

There is another consideration for people who have had a hamstring graft. We need to look at how well you can control your hamstrings in deeper knee flexion. This is not just about moving from full extension to 90 degrees. We are also interested in what happens as your heel gets closer to 110 or 120 degrees and you actively contract your hamstrings.

With a hamstring graft, part of the medial hamstring is harvested as the donor tissue. This creates weakness at the donor site and can also affect the deeper ranges of motion that the hamstrings help control. We need to assess this more closely, particularly in athletes who rely on sprinting and other movements that require substantial knee flexion.

I have had hamstring grafts on both sides, so this is something I have experienced myself. I still have some residual weakness, and I have a history of hamstring strains. Before, I did not fully understand why. Now, working in this space, I understand the importance of assessing deeper knee flexion and hamstring strength after a graft.

The research supports this concern. A randomized controlled trial by Tashiro and colleagues found that hamstring strength was significantly lower at 70 degrees of knee flexion or more after tendon harvest. The loss was greater when two tendons, the gracilis and semitendinosus, were harvested compared with just one.

A more recent study by Hu and colleagues found a strength deficit at 90 degrees of approximately 38 percent when two tendons were harvested, compared with about 25 percent when one tendon was harvested. These deficits are important to assess, especially in deeper knee flexion. For athletes who sprint frequently, we need to make sure they can regain the necessary strength and control to move through that full flexion cycle.

Otherwise, they may compensate or place more stress on the hamstrings. This is another reason why restoring knee flexion is not simply about being able to touch your heel to your butt. We also need to understand what you can actively control in that range.

Now let us talk about how to interpret your results and what to do next. Think of three categories: green, yellow, and red.

Green means your tests match the other side. You have a soft end feel, your hips and pelvis stay level, your weight is even, and both knees feel the same. That is great. Continue checking your range of motion periodically, then shift more of your attention toward the other priorities in your rehabilitation.

Yellow means you are close, but something is still off. Your pelvis shifts, there is a gap between your butt and heels, your weight moves toward the uninvolved side, or you feel more pressure at the front of the involved knee. You may also notice that your active heel slide stops short of your passive heel slide.

This is where I think most people fall. They tell me they have their flexion back, but when we look more closely, they are only about 80 percent of the way there. They can rock back and feel like they have reached the position, but the video shows the pelvis shifting. That is not a failure. It is information we can use.

In most of these cases, people can restore the remaining range. If you have reached 120 degrees, or even 125 to 130 degrees, and you are not running into a significant hard wall, there is a good chance you can continue making progress with the right prescription, frequency, and consistency. It may not happen in a week, but people can regain their flexion even when they are weeks, months, or years out from surgery.

We have worked with people who are one, two, three, five, and even ten years out from their injury or surgery and have never fully restored their knee flexion. They may think that the opportunity has passed. In reality, with consistent work, appropriate progression, and attention to how the knee responds, they can still make meaningful improvements.

Red means we need to look more closely at what is limiting the movement. If passive bending is limited, I look at the joint first. Is there swelling? Is the knee guarding? Are the surrounding muscles, such as the hamstrings, quadriceps, or calves, protecting the joint? We also need to consider how the knee has been managed in terms of overall loading.

If passive flexion is available but active flexion is limited, I think more about muscle control and strength, particularly the hamstrings and their ability to work in deeper ranges of motion.

If you fall into the yellow category, here are four rules to follow.

Rule one: Do not crank on it. I want to repeat that. Do not crank on your knee. This means forcing it into more bend while you are awake, whether you are doing it yourself, someone is leaning on it, or your physical therapist is applying force.

That is different from a manipulation under anesthesia or MUA, which is a procedure performed by a surgeon while you are asleep. It may be used to address restrictions related to scar tissue. I will come back to that shortly.

When someone forces the knee into a deeper bend, they might temporarily gain some range of motion. It may look better when measured immediately afterward, but the knee can flare up a few hours later. The surrounding muscles may begin guarding, and the range can rebound. You end up taking one step forward and one or two steps backward.

That back-and-forth is what forcing the range can create. In my clinical opinion, cranking on the knee is not what gets it to full flexion, and it is not something we endorse at The ACL Athlete.

We have worked with some of the most challenging flexion cases as a team. The knees that eventually regained their range did so through gradual, tracked work and frequent, smaller doses. Some took months, but they got there. The same principle can apply to extension, although we see this issue more often with flexion.

Rule two: Frequency over intensity. Instead of doing 30 minutes of flexion work once a day, or an hour once or twice a day, break it into smaller sessions. Depending on your schedule and how your knee responds, that might mean three to five sessions a day or even six to ten sessions.

You might start with five to ten minutes per session, spread throughout the day. Each short session gives you feedback. Is the knee flared up from rehabilitation, a long day on your feet, or something you pushed too hard earlier? You can use that information to adjust the next session.

You are essentially learning to auto-adjust based on the feedback from your knee instead of following the exact same routine regardless of how you feel. One large dose may push you too far, leaving you waiting for the knee to settle down. Microdosing allows you to nudge the range forward, see how the knee responds, and make adjustments along the way.

Rule three: Play the one-degree-a-day game. In the first few days, you may see bigger jumps in range of motion. That is common. I am not saying you will gain exactly one degree every day from the moment of surgery. Instead, this is a useful mindset, particularly after you have reached 90 degrees.

Getting to 90 degrees happens relatively quickly for many people. After that, think about gaining one degree at a time rather than trying to get another 10 or 15 degrees in a single day. If you are at 120 degrees and working toward 140 or 145 degrees, even a one-degree-a-day mindset means you could get there over approximately 20 to 25 days.

That does not mean progress will follow a perfectly linear pattern. Your range will fluctuate, and you will be doing other things in rehabilitation that influence how your knee responds. The point is to nudge the range forward gradually instead of feeling like you need to force a major improvement by the end of every week.

Small, consistent doses tend to be better tolerated than large, intense bouts of stress. Give your knee frequent opportunities to move into the range without repeatedly forcing it into a position it does not tolerate well.

Rule four: Get the swelling down. When your knee bends, the pressure inside the joint increases. A swollen knee can feel like a tight balloon, and that swelling can limit your range of motion no matter how hard you work.

I believe many people could do a fraction of the range-of-motion work they are currently doing, get their swelling under control, and end up with better extension and flexion. I see this with our athletes. Sometimes they reduce the amount of work they are doing, but once we get the knee quiet and calm, their quad set, extension, and flexion improve.

When swelling and pain decrease, the muscles can function more effectively, and there is less pressure inside the joint. That creates a better environment for the knee to move through its available range.

One way we track swelling is with the sweep test, also called the stroke test. You sweep upward along the inside of the knee and then downward across the top of the kneecap on the outside. You then look at the inside of the kneecap for a small dip or sulcus and observe whether fluid returns.

There is a grading scale for the sweep or stroke test that you can use to track swelling over time. You do not necessarily need to be perfect at grading it yourself, but you should understand the trend. Swelling assessment is part of your range-of-motion plan, and load management is one of the biggest factors we address.

When should you stop managing this yourself and bring someone in? I would say you should always have a qualified professional involved, ideally a physical therapist or coach who understands ACL rehabilitation. But there are some specific situations where we need to create more urgency.

First, if you are still below 90 degrees during the first six to eight weeks, that deserves attention. This is a general guideline, and every case is different. If you are stuck at 60 or 70 degrees during the first four to six weeks, your physical therapist should be assessing the situation and helping establish clear expectations.

You want to look at passive and active range of motion, your symptoms, the details of your procedure, and the trend over several weeks. Slow but steady progress can be acceptable. However, if you have been sitting at 60, 70, or 90 degrees for weeks without any meaningful improvement, we need to investigate further.

Second, if you repeatedly hit a wall with your flexion, get it assessed. Third, if you remain stuck at 90 degrees beyond eight weeks, I want more insight from your surgeon.

Fourth, around the three-month mark, we need to look more closely at the overall picture. If your progress has not moved toward the general benchmarks of 90 and 120 degrees, we may start asking whether additional imaging is necessary.

This is not an automatic decision based on time alone. We need to consider the full clinical picture before bringing up imaging. Have you been doing the appropriate work? Have you managed your overall loading so the knee is not constantly flared up? What have your symptoms been doing? What does the range-of-motion trend show?

We do not want you to spend another three months simply hoping things will improve if there are patterns suggesting that we need more answers. Sometimes additional imaging is appropriate, but imaging itself is not a shortcut. It needs to be considered alongside your symptoms, rehabilitation history, and objective measurements.

Here is the honest part: some knees are just difficult. For some people, flexion returns, but it takes months. A smaller group may need a procedure to get past a persistent mechanical limitation, such as scar tissue. There may also be an issue with a meniscus repair or another problem that needs to be investigated.

In some cases, the restriction is related to scar tissue, and the surgeon may consider a manipulation under anesthesia or a surgical clean-out of the scar tissue. That decision belongs to the surgeon. Many people do continue making progress without a procedure, even if they are slower responders. The important thing is to identify whether you are someone who needs further assessment or someone who simply needs more time and the right rehabilitation approach.

The way we make that distinction is through tracking. This is where objective measurements become so important. It is surprising how often people do not know their range-of-motion numbers or whether their physical therapist is tracking them.

Imagine a company saying it made more money this month but having no numbers to support the statement. Or imagine someone in the hospital being told that their white blood cell count is high without being given an actual measurement. How would you know what that means? Is it a normal finding, something that needs attention, or something more serious?

We need numbers to give context to our decisions and determine what the plan and exercise prescription should look like. It is mind-boggling to me when people do not have objective measurements associated with their range of motion, symptoms, and, when appropriate, quadriceps and hamstring strength.

These measurements should be a standard part of ACL rehabilitation. We need numbers supported by research and measured through valid and reliable processes. We should be tracking symptoms, range of motion, swelling, and the trend over time. Strength should also be included when the athlete is at the appropriate stage to assess it.

That full picture helps us decide whether you should continue working gradually on your flexion or whether we need to pursue the next steps to understand why it is not progressing. Without measurements, you are essentially guessing. You might rush into a procedure you did not need because there was not enough context, or you might wait too long before pursuing a procedure that was necessary.

This is why I want you to have the tools and information to support conversations with your surgeon or physical therapist.

For your follow-up assessment, the tall kneeling rock back should remain one of your main checks. Early in the process, you can formally audit your flexion weekly. Once things are moving well, revisiting it every two to four weeks should be enough, and you may need to check it less often later in rehabilitation as long as everything continues to look good.

You do not need to create a separate routine for this. You are already performing range-of-motion work on most days, so you can continue checking how the knee responds. The formal recheck is simply a recorded snapshot that allows you to compare your movement over time.

Use the same setup each time. Position your phone behind you, and add a second angle from the side if possible. Look at five things: Is your pelvis level? Is the pressure equal through both knees and heels? Does your butt touch your heels without a gap? Can you sit comfortably in that position? And does the knee feel the same as the other side?

Write down the date, record a yes or no for each item, and add any relevant notes. Include your swelling grade as well. Take a baseline video today. When you compare it with another video a few weeks later, you may notice things that you cannot reliably identify just by how the movement feels.

That tracking log is also something you can bring to your surgeon or clinician if your progress is not moving forward. You will have objective information and visual evidence rather than relying entirely on how you think the knee feels.

In my experience, when people stop cranking on the knee, switch to frequent smaller doses, manage their swelling, and control their overall loading, their flexion often responds positively. That means paying attention not only to your rehabilitation exercises but also to how much you are walking, how long you are standing, and how much stress you are placing on the knee throughout the day.

I cannot control the biological factors involved if something like scar tissue begins to form. But you can create a much better environment for recovery by managing your symptoms, swelling, pain, and overall loading during those first four, six, and eight weeks. You also need an appropriate exercise prescription.

A lot of people tell me they are doing their flexion exercises, but when we look more closely, they are not necessarily doing the right exercises in the right sequence. Sometimes the dosage is simply off. They are doing things ad hoc, performing intense bouts, or holding certain positions longer than they need to.

The way I look at this is through dosage. When we talk about medicine, the difference between something that helps and something that becomes harmful often comes down to the dose. If you titrate the dose too low, it may not be effective. If you push it too high, it can become counterproductive.

That level of detail is essential in ACL rehabilitation. The prescription, how the exercises are programmed, how they are structured throughout your day, and how they fit into the bigger picture all matter. Many people collect exercises from Instagram, TikTok, YouTube, or their physical therapist and end up with a hodgepodge of movements without a clear plan.

But the knee and the body respond to specific stimuli. We have to be intentional about how we apply those stimuli by understanding the human body, the ACL rehabilitation process, and the individual context of the person. That is where the dosage becomes so important.

As we bring this to a close, here are the five main takeaways:

First, extension comes first and flexion comes second, but both should be addressed regularly. We are not choosing one over the other. We are following a priority list.

Second, your target is your other knee. Look for your heel to reach your butt, your calf to meet your hamstrings, and a soft, bouncy end feel. Use the strap-assisted heel slide, the active heel slide, and the tall kneeling rock back with a video recorded from behind to assess your movement and pelvic position.

Third, do not crank on your knee. Use smaller, frequent doses of range-of-motion work. Think about the one-degree-a-day mindset rather than trying to force large gains in a single session.

Fourth, get the swelling down. Manage your overall loading and pay attention to how your knee responds throughout the day.

Fifth, pay attention to the trend in your measurements. If you are below 90 degrees during the first six to eight weeks, stuck at 90 degrees beyond eight weeks, or not progressing toward the general benchmarks during the first three to four months, bring your surgeon and physical therapist into the conversation. Track your range of motion, symptoms, and swelling so you have objective information to share.

Your homework is to perform these three tests and record your tall kneeling rock back. If your pelvis shifts, there is a gap, or the movement does not look like the other side, you have identified something that needs attention.

I would encourage you to work with a qualified physical therapist who understands how to address this type of limitation. It is not simply a matter of doing a towel exercise, rocking back onto your heels, or forcing the knee to bend. There are many nuances involved. We need to assess the limitation properly and determine what will help remove that bottleneck and move your recovery forward.

The dosage is going to be key. If you found this helpful, please reach out and let me know. If you found it confusing, reach out and let me know. I wanted to give you a deep dive into knee flexion so you can assess it yourself and, just as importantly, avoid panicking if you have not restored it within the first couple of weeks.

I hope this helps you audit your knee flexion and make sure you get it back. I do not think getting 80 percent of the way there in ACL rehabilitation is the goal. You need to get back to who you were before the injury, and honestly, even better than that. With the right guidance, that is very doable.

If you need any help, please reach out to us. We are here to help. Otherwise, I will catch you in the next episode. This is your host, Ravi Patel, signing off.