Why Is My Knee Still Stiff After Knee Replacement?
- Tom Morgan, Chartered Physiotherapist
- Aug 9
- 3 min read
Stiffness after knee replacement is extremely common, particularly in the first weeks. The joint has undergone major surgery, swelling restricts movement and the surrounding muscles can remain protective and weak.
What matters is not whether the knee feels stiff today. It is whether the overall trend is gradually improving.
Swelling is a major cause of stiffness
A swollen knee often feels tight before it feels painful. The fluid around the joint makes bending physically harder and can also inhibit the quadriceps.
Swelling typically peaks early and then reduces over weeks to months rather than disappearing in a few days.
Your knee may be stiffest at certain times
Many people notice more stiffness first thing in the morning, after sitting for a long time or later in the day when swelling has accumulated. This fluctuation is common.
Pain can make you guard the movement
If bending has been painful, you may naturally stop short of the available range. Regular, tolerable movement helps prevent this protective pattern becoming established.
Pre-operative movement matters
Someone who entered surgery with a very stiff arthritic knee may not follow the same range-of-movement timeline as somebody who had much better movement beforehand. Recovery should be judged against your own starting point.
Want the full knee replacement recovery plan?
Keep working on both flexion and extension
Heel slides, cycling when appropriate and progressive functional exercise can help flexion. Extension work and quadriceps activation help the knee regain straightening.
A programme focused on only one direction can leave an important deficit unaddressed.
Do not mistake more pain for better stretching
Aggressively forcing the knee is not automatically more effective. If an exercise causes a large inflammatory flare, the additional swelling can make the joint feel even stiffer afterwards.
Strength affects how the knee feels
A weak knee can feel stiff or reluctant even when the passive range is reasonable. As quadriceps and hip strength improve, many movements begin to feel smoother and more confident.
How long can stiffness last?
Some stiffness and swelling can remain for several months. Range of movement is usually becoming increasingly established through the first six months, with final range often well established by six to twelve months.
When does stiffness need review?
If the knee is becoming progressively stiffer rather than more mobile, if flexion remains very restricted and is limiting important activities, or if you lose movement you had previously gained, contact your physiotherapist or surgical team.
When should you seek further advice?
Recovery is rarely a perfectly straight line, but new or rapidly worsening symptoms should not simply be pushed through. Contact your surgical team, GP or physiotherapist if pain, swelling, movement or function is moving in the wrong direction rather than gradually improving. Seek urgent medical attention for symptoms such as sudden breathlessness or chest pain, marked one-sided calf swelling, a hot increasingly red joint with fever, sudden loss of function, or other symptoms your surgical team has told you require urgent review.
Want the full knee replacement recovery plan?
This article provides general information and does not replace advice from your own surgeon, physiotherapist or medical team. Recovery varies between individuals and any specific restrictions or weight-bearing instructions from your surgical team should take priority.
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