Knee Replacement Recovery: More Means Better
Key insights: 60-second read
- More exercise equals more motion - People who did high-frequency knee flexion exercises (about 5 times per day) gained 14.2 degrees of flexion compared to 10.1 degrees in the low-frequency group (about 2 times per day) - a difference of 4.1 degrees.
- Even small improvements matter - A 4-degree gain in knee flexion can be clinically meaningful for everyday activities like sitting, standing, and climbing stairs.
- Both groups improved significantly - All participants benefited from the 18-day rehabilitation program, showing improvements in walking distance, strength, and quality of life.
- The "more is better" principle applies - Participants with worse knee flexion at baseline showed greater improvements, supporting the idea that those who need it most benefit the most from extra exercise.
- Real-world adherence matters - The high-frequency group averaged 5.3 sessions per day, not the planned 8. This reflects the reality of home exercise programs and the importance of setting achievable goals.
If you've had a knee replacement, you'll know that getting your knee to bend properly is one of its biggest challenges. You might have been told to do your exercises. But how much is enough? Does doing more actually make a difference?
A new randomised controlled trial published in Physiotherapy Research International (Mogensen et al., 2025) set out to answer this question. The researchers compared high-frequency versus low-frequency self-managed knee exercises in people who had restricted knee flexion (105 degrees or less) after a total knee replacement.
The findings are clear: more exercise led to more motion. The high-frequency group gained an average of 14 degrees of knee flexion, compared to 10 degrees in the low-frequency group - a difference of 4 degrees.
While 4 degrees might not sound like much, it can make a real difference in everyday activities like getting out of a chair, climbing stairs, or even riding a bike.
"In individuals with reduced joint mobility after TKA, high frequency self-managed knee flexion exercises were associated with a positive change in flexion compared with low frequency." - Mogensen et al., 2025
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What the study found
Researchers recruited 83 people who had undergone a total knee replacement within the previous 6 to 26 weeks and had limited knee flexion (105 degrees or less). All participants took part in an 18-day inpatient rehabilitation program.
They were randomly assigned to one of two groups:
- High-frequency group (HF): Asked to do their knee flexion and extension exercises eight times per day
- Low-frequency group (LF): Asked to do their knee flexion and extension exercises two times per day
Both groups did the same exercises - just at different frequencies. The exercises were simple and could be done at home with no special equipment: standing on stairs to bend the knee, lying on a couch with the leg on a frame, and sitting exercises to improve extension.
Data from Mogensen et al. (2025) .
The high-frequency group achieved an average of 5.3 sessions per day (not the full 8 they were asked to do). The low-frequency group achieved 1.7 sessions per day - close to their target of 2.
Both groups improved significantly in secondary outcomes like walking distance, leg strength, pain, and quality of life. But there was no significant difference between the groups on these measures. This suggests that the basic rehabilitation program was effective for overall function, but the extra frequency specifically helped with knee flexion.
How the study worked
The study was conducted at a rehabilitation centre in Spain affiliated with the Danish public healthcare system. All participants were admitted for an 18-day inpatient program.
The exercises were simple and easy to replicate at home:
Flexion exercises (choose one):
- a) Staircase flexion: Stand on stairs with the operated leg two steps up. Move your body forward until you feel a stretch, keeping your knee aligned with your foot.
- b) Böhler frame flexion: Lie on your back with the operated leg on a knee flexion frame (or a rolled towel). Use the other foot to gently press the operated foot down into more flexion .
Extension exercises (choose one):
- c) Heel prop extension: Sit or lie with a rolled towel under your heel. Actively press your knee down into extension.
- d) Chair extension: Sit on a chair with the operated leg extended forward. Use your hands to apply gentle pressure above the knee to improve extension.
Each exercise was performed for 10 repetitions per session, holding the end-range position for 10 seconds, with a 3-5 second pause between repetitions.
In addition to these specific exercises, all participants received a standardised rehabilitation program: daily 45-minute supervised group sessions, gym-based strength training, and educational sessions.
Why this matters for you
After a knee replacement, regaining movement is critical. Achieving approximately 110 degrees of knee flexion allows you to perform routine activities of daily living: sitting and standing from a low chair, walking, climbing stairs, and cycling.
But not everyone gets there. Some people end up with stiff knees that limit their function and quality of life. This study focused on exactly that group - people who were struggling with limited flexion weeks after surgery.
The key message is this: doing more exercises can help you get more movement. The high-frequency group gained an extra 4 degrees of flexion compared to the low-frequency group. While 4 degrees might seem small, it can be clinically meaningful. Some studies suggest that a change of 3 to 6 degrees can be important for people with knee osteoarthritis.
Even more importantly, people with the worst flexion at the start of the study showed the greatest improvements. This means that if you are struggling, extra exercise might help you the most.
Key point
"A significant (p = 0.004) correlation of r = 0.311 was observed between a lower baseline flexion and a greater improvement." - Mogensen et al., 2025
A physio's perspective: the more you move it, the better
When it comes to joint recovery - especially after surgery - the more you move it, the better it gets. As annoying as this phrase is - motion is lotion.
This study suggests that the people who do their exercises - tend to do better.
But here is the nuance. It is not just about doing any exercise. It is about doing the right exercise at the right frequency. The exercises in this study were specific: they targeted end-range flexion and extension. They were done multiple times a day. They were simple and could be done anywhere.
The study also shows that the high-frequency group didn't quite reach the target of 8 sessions per day - they averaged 5.3 . This is realistic. It shows that even if you don't hit the target perfectly, you can still get benefits. Consistency matters more than perfection.
"In my clinical experience, the more you move it, the better it gets. I have seen this with knees, shoulders, hips, and backs. Movement begets movement. Motion is lotion." - Grant Frost, Musculoskeletal Physiotherapist
Practical tips for knee replacement recovery
Based on this study and my clinical experience, here are some practical tips for anyone recovering from a knee replacement:
1. Do your exercises frequently, not just once a day. The study showed that doing exercises multiple times a day (5-8 sessions) was more effective than doing them once or twice. Spread them throughout the day.
2. Focus on end-range. The exercises in this study were designed to push the knee to its end-range of motion. This is where the gains happen. Don't just go through the motions - work on getting a little further each time.
3. Expect some discomfort. The study noted that pain or tightness at end-range during exercises could occur and that temporary knee irritation might be experienced immediately after exercise. This is normal. The key is that the irritation should subside before the next session .
4. Use simple, equipment-free exercises. You don't need expensive equipment. A staircase, a chair, and a rolled towel are enough. The exercises in this study were designed to be accessible and easy to integrate into daily life.
5. Track your progress. The study used a logbook to monitor exercise frequency. Keeping a simple record can help you stay accountable and see your progress over time.
6. Don't neglect extension. Both groups improved their knee extension, but the extension exercises were done less frequently than the flexion exercises. Good extension is just as important as flexion for walking and standing.
7. Stay active overall. The basic rehabilitation program - including walking, strength training, and balance exercises - also contributed to improvements. The specific flexion exercises were an addition to a comprehensive program, not a replacement for it.
Frequently asked questions
How often should I do my knee exercises after a replacement?
This study suggests that doing knee flexion exercises 5-8 times per day is more effective than doing them once or twice a day. However, the high-frequency group averaged 5.3 sessions, not the full 8. Aim for multiple sessions throughout the day rather than one long session.
Is pain during exercise normal?
Some pain or tightness at end-range is normal and expected. The study noted that temporary knee irritation might be experienced immediately after exercise, but it should subside before the next session. If pain is severe or persistent, consult your physiotherapist.
How long does it take to see improvement?
In this study, participants showed significant improvements over 18 days. The greatest improvements typically occur in the first 4-6 weeks after surgery, but this study shows that even people who are 14 weeks post-surgery can still make meaningful gains.
What if I can't do the exercises because my knee is too painful?
Start gently. The study noted that pain levels were generally low after surgery, suggesting that pain was not the main barrier. If pain is limiting you, speak to your physiotherapist. They can help you modify the exercises or address the underlying cause of the pain.
This study provides clear evidence that doing more knee flexion exercises may lead to better knee motion after a total knee replacement. The high-frequency group gained 14.2 degrees of flexion compared to 10.1 degrees in the low-frequency group - a difference of 4.1 degrees.
While 4 degrees might not sound like much, it can make a real difference in everyday activities. And for people who are struggling with stiff knees, the extra effort is worth it.
The key message is simple: the more you move it, the better it should get. Movement begets movement. Motion is lotion. If you have had a knee replacement, do your exercises frequently, push to end-range, and stay consistent. Your knee will thank you.
If you would like personalised guidance on your knee recovery or any other aches and pains, I am here to help.
- Grant
Living With Persistent Pain?
If your pain has lasted longer than expected, feels disproportionate to injury, or hasn't responded to standard treatment, you may benefit from a broader approach. Learn more about our knee pain physiotherapy services in Port Macquarie.
Want personalised guidance?
If you would like help making sense of your aches, pains, or ongoing symptoms, you can book with Grant either in Port Macquarie or via telehealth.
Disclaimer: This information is for educational purposes and does not replace individualised medical advice. If you have persistent pain or other concerning symptoms, consult a qualified healthcare professional. This blog post summarises a published research study; the original source should be consulted for full methodological details.
