If you're preparing for or recovering from knee replacement surgery, you've probably heard your care team talk a lot about range of motion—but what does that really mean, and why does it matter so much?
Let’s break it down.
What Is Range of Motion?
"Range of motion" (or ROM) simply refers to how far your knee can bend and straighten. After surgery, it’s important for your new joint to regain as much movement as possible so you can walk, climb stairs, sit, and get back to the daily activities you enjoy.
Ideally, most people can achieve about 0° (fully straight) to 120° (a strong bend) of knee motion after surgery. This allows for a normal walking pattern and the ability to sit and stand comfortably.
Why It Matters After Knee Replacement
Restoring range of motion is one of the top priorities after a total knee replacement. Why? Because limited motion—often called stiffness—can become a major complication. According to a 2023 study published in The Journal of Arthroplasty, stiffness affects around 6.1% of patients after knee replacement surgery.
Patients who develop stiffness may struggle with basic movements, experience pain, and in some cases, need additional procedures like:
Manipulation under anaesthesia (MUA) – where the knee is moved while you're under sedation to break up scar tissue.
Reoperations such as arthroscopy or revision surgery to improve knee motion.
The High Cost of Stiffness
The same study found that stiffness doesn't just affect your recovery—it can be expensive.
Here are some eye-opening stats:
Patients with knee stiffness were over twice as likely to need a second surgery compared to those without stiffness.
On average, patients with stiffness faced treatment costs 1.5 to 7.5 times higher than those who recovered with good motion.
The cost of revision surgery in stiff knees could be as high as $65,771, significantly more than in non-stiff knees.
Even patients who didn’t require another surgery but had stiffness still spent nearly $4,000 more on rehabilitation, medications, and other treatments within two years.
In other words, keeping your knee moving isn’t just about comfort—it’s about avoiding complications, extra procedures, and financial stress down the track.
What You Can Do to Protect Your Motion
The good news is, you can take steps to protect and improve your knee’s range of motion:
Start early: Gentle movements and physiotherapy usually begin shortly after surgery.
Stay consistent: Stick with your exercises even when it's tough—your hard work will pay off.
Follow your rehab plan: Your physio or surgeon will tailor your recovery plan to your specific needs.
Speak up: If you feel your knee isn't bending or straightening the way it should, tell your care team early.
Bottom Line
Range of motion after knee replacement is crucial—not just for mobility, but also to avoid the high costs and risks linked to stiffness. With early action, consistent rehab, and the support of your healthcare team, you can give your new knee the best chance at a smooth, functional recovery.