Frequent Mobility Exercises Added Only Four Degrees of Knee Flexion After Total Knee Replacement
Reduced range of motion is common after total knee replacement. Many people experience stiffness, swelling, and difficulty bending the knee, particularly during the first months after surgery. Limited knee flexion may make stair climbing, rising from low chairs, putting on shoes, and other daily activities more difficult.
⠀
A randomised controlled trial examined whether people with restricted knee flexion should complete self-directed mobility exercises eight times per day rather than twice per day. All participants were between six and 26 weeks after surgery and attended an 18-day rehabilitation programme.
⠀
The high-frequency group improved knee flexion by an average of 14.2 degrees, compared with 10.1 degrees in the lower-frequency group. The difference between the groups was therefore 4.1 degrees.
⠀
However, the additional range of motion did not produce clear benefits in walking capacity, sit-to-stand performance, pain, self-reported knee function, or knee-related quality of life. More daily exercise sessions may therefore provide a modest additional improvement in joint range without necessarily improving short-term function.
⠀
Why Can the Knee Become Stiff After Surgery?
After knee replacement surgery, the body responds with pain, swelling, and a normal inflammatory healing process. These factors may reduce muscle activation and make it uncomfortable to move the knee through its available range.
⠀
Postoperative mobility may also be influenced by the range of motion available before surgery. A person with severe preoperative stiffness may not regain unrestricted flexion immediately after the procedure.
⠀
Factors that may influence knee mobility include:
• Preoperative range of motion
• Pain and swelling
• Scar formation and tissue healing
• Muscle activation and strength
• Daily use of the knee
• Fear of bending or loading the joint
• Postoperative complications
⠀
Some people develop extensive scar tissue and persistent stiffness. Most experience gradual improvement through healing, activity, and rehabilitation.
⠀
How Much Knee Flexion Is Required?
The amount of flexion required varies between activities and individuals. Ordinary walking requires less movement than stair climbing, low chairs, or activities close to the floor.
⠀
A person may have measurable restriction but still manage essential daily activities. Another person may have greater range of motion but remain limited by pain, weakness, or poor confidence.
⠀
Approximate requirements may include:
Activity | Typical knee-flexion requirement |
Level walking | Approximately 60 degrees |
Stair climbing | Approximately 80–100 degrees |
Rising from a chair | Often around 90 degrees or more |
Low chairs or deeper squatting | Greater flexion required |
Kneeling or floor-level activity | May require substantial flexion |
⠀
These figures are approximate and are influenced by chair height, body proportions, strength, and movement strategy.
⠀
Who Participated in the Study?
The study included 83 people who had undergone total knee replacement. Their mean age was 65 years, and 70% were women.
⠀
Participants were between six and 26 weeks after surgery and had knee flexion of 105 degrees or less. The study therefore focused on people whose range of motion remained below the desired level during the early or intermediate rehabilitation phase.
⠀
Everyone attended an 18-day multidisciplinary rehabilitation programme. They therefore received additional treatment and exercise alongside the self-directed mobility exercises being compared.
⠀
Group | Participants | Planned frequency |
High-frequency group | 44 | Eight sessions per day |
Lower-frequency group | 39 | Two sessions per day |
⠀
The study compared different exercise frequencies rather than exercise versus no exercise.
⠀
The Exercises Were Self-Directed
Participants completed active knee-flexion and knee-extension exercises throughout the day without continuous supervision from a physiotherapist.
⠀
This approach has practical advantages. Mobility exercises generally require little equipment, and brief sessions can be distributed across the day. However, the outcome depends on whether the person remembers the exercises and moves through a sufficient range.
⠀
The high-frequency group actually completed an average of 5.3 sessions per day rather than the planned eight. The lower-frequency group completed an average of 1.7 sessions.
⠀
The real difference was therefore closer to five sessions versus two sessions per day.
⠀
Knee Flexion Improved in Both Groups
Both groups achieved meaningful improvements in knee flexion during rehabilitation.
⠀
Change in knee flexion | Result |
High-frequency group | 14.2 degrees |
Lower-frequency group | 10.1 degrees |
Between-group difference | 4.1 degrees |
⠀
The difference was statistically significant. This suggests that more frequent short mobility sessions may produce slightly greater improvement than approximately two daily sessions in people with restricted flexion.
⠀
Is a Four-Degree Difference Important?
Statistical significance does not automatically mean that the difference is large enough to matter in daily life. The relevance of four degrees depends on the person’s starting point and functional goals.
⠀
A few additional degrees may help someone who is just below the range required for a particular chair or stair task. For another person who remains limited mainly by weakness, pain, or balance, the difference may have little practical effect.
⠀
The absence of a clear difference in the functional tests suggests that the additional flexion did not produce a noticeable functional advantage during the short study period.
⠀
The most accurate conclusion is therefore that higher frequency modestly improved range of motion, while the clinical importance remained uncertain.
⠀
Walking Capacity Did Not Improve More
Participants completed the six-minute walk test, which measures how far a person can walk in six minutes. Performance is influenced by endurance, pain, strength, balance, and walking confidence.
⠀
Both groups improved, but there was no clear difference between them. The additional knee flexion in the high-frequency group did not enable participants to walk further than those completing fewer sessions.
⠀
Walking function is not determined by knee mobility alone. Level walking requires a relatively moderate amount of flexion, and other limitations may become more important once sufficient movement is available for stepping.
⠀
Sit-to-Stand Performance Was Also Similar
Researchers used the 30-second sit-to-stand test to record how many times participants could rise from and return to a chair.
⠀
Both groups improved, but higher exercise frequency did not provide an additional benefit.
⠀
Sit-to-stand performance depends on:
• Thigh and hip strength
• Chair height
• Movement speed
• Balance during the transition
• Pain and confidence
• Ability to load the operated leg
⠀
Greater flexion may help when range is severely restricted. Once a minimum range has been achieved, strength and movement control may become more important.
⠀
Pain and Self-Reported Function Were Similar
Pain was measured using a numerical rating scale, while knee function was assessed with the Knee Injury and Osteoarthritis Outcome Score. This questionnaire includes pain, symptoms, activities of daily living, and knee-related quality of life.
⠀
Both groups improved, but there were no reliable differences between them.
⠀
More frequent sessions therefore did not cause greater pain, but they also did not produce better pain relief or self-reported function than the lower-frequency programme.
⠀
The findings do not support the idea that completing only two daily mobility sessions necessarily produces worse short-term pain or overall knee function during this rehabilitation phase.
⠀
The Study Examined Frequency and Total Exercise Exposure
The high-frequency group moved the knee more often throughout the day. Frequent movement may have reduced the amount of time the knee remained in one position and provided repeated stimulation of the tissues.
⠀
However, the study did not establish that total exercise time, repetitions, and intensity were identical apart from frequency. The group completing more sessions may also have received a larger total training dose.
⠀
The result may therefore reflect:
• More frequent periods of movement
• More total repetitions
• Less time with the knee held still
• Greater attention to mobility
⠀
The study cannot identify which factor was most important.
⠀
More Sessions Are Not Appropriate for Everyone
Some people tolerate frequent short sessions well. Others may experience increased pain, swelling, or irritation when the dose is raised too quickly.
⠀
The response should be assessed both during the exercise and later in the day. A moderate and temporary increase in discomfort may be acceptable, while clear and persistent deterioration may indicate excessive loading.
⠀
The programme may be adjusted through:
• Fewer repetitions per session
• Less force at the end of the range
• Longer rest periods
• Fewer daily sessions
• Alternating movement and elevation
• Adjustment according to swelling and daily symptoms
⠀
The objective is consistent progress rather than forcing the knee as far as possible during every session.
⠀
Mobility Exercises Should Be Combined With Functional Rehabilitation
Knee flexion is important, but rehabilitation after total knee replacement should also address strength, balance, walking, and activity tolerance.
⠀
A broader programme may include:
• Active knee flexion and extension
• Strength training for the thighs and hips
• Sit-to-stand exercises
• Walking practice
• Stair training when relevant
• Balance exercises
• Gradual increases in daily activity
⠀
Mobility work should support functional goals. Spending a large proportion of rehabilitation time pursuing a few additional degrees may be less useful when strength or walking capacity is the main limitation.
⠀
When Should Persistent Stiffness Be Assessed Further?
Recovery varies, but movement should generally improve over time. When progress stops, the physiotherapist may need to assess exercise dosage, pain, swelling, and technique.
⠀
Medical assessment may be required when there is:
• Rapidly increasing pain or swelling
• A hot, red knee with systemic illness
• Wound discharge or healing problems
• Sudden loss of previously achieved movement
• New inability to bear weight
• Severe persistent restriction despite rehabilitation
⠀
Increasing exercise frequency should not delay assessment of possible complications.
⠀
Important Limitations
All participants attended an 18-day inpatient or residential rehabilitation programme. Results may differ for people exercising independently at home without extensive support.
⠀
Only people with flexion of 105 degrees or less between six and 26 weeks after surgery were included. The findings may not apply to the immediate postoperative period or to people who already have good mobility.
⠀
Participants did not fully complete the planned frequency. The actual comparison was approximately five versus two sessions per day rather than eight versus two.
⠀
Follow-up was short, so it is unknown whether the four-degree difference remained after several months.
⠀
Participants knew their group allocation, and adherence was based on self-report.
⠀
The trial was primarily designed to assess knee flexion. Smaller differences in secondary functional outcomes may have been missed.
⠀
What Do the Findings Mean in Practice?
The study supports the use of several short daily mobility sessions when restricted knee flexion is a clear rehabilitation problem.
⠀
The expected additional benefit should remain realistic. More frequent exercise produced approximately four extra degrees of flexion but no documented improvement in pain, walking, sit-to-stand performance, or self-reported function.
⠀
Frequent sessions may be useful when the exercises are well tolerated and mobility is the main limitation. If they increase swelling, consume excessive time, or replace strength and functional training, the dose should be reconsidered.
⠀
Summary
A randomised controlled trial included 83 people with knee flexion of 105 degrees or less between six and 26 weeks after total knee replacement.
⠀
Participants were assigned to self-directed knee-flexion and knee-extension exercises planned either eight or two times per day during an 18-day rehabilitation programme.
⠀
The groups actually completed an average of 5.3 and 1.7 sessions daily. Knee flexion improved by 14.2 degrees in the high-frequency group and 10.1 degrees in the lower-frequency group, producing a 4.1-degree difference.
⠀
There were no clear differences in knee extension, walking capacity, sit-to-stand performance, pain, or self-reported knee function.
⠀
Frequent mobility exercises may therefore provide a modest additional improvement in knee flexion, but the study did not show that the extra range improved short-term function.
⠀
Sources
Mogensen, L., Rasmussen, T., Rasmussen, J., & Molsted, S. (2026). Efficacy of active exercises to improve range of motion in knee joint after total knee arthroplasty: A randomized controlled trial. Physiotherapy Research International, 31(3), e70228. https://doi.org/10.1002/pri.70228
⠀
