Life with a knee replacement: 25 patient questions
Why does the knee hurt at night? Can I have an MRI? How can implant instability be recognised, and how many years will the implant last?
After knee replacement, attention gradually shifts from the first steps to longer-term life with an implant. Questions arise about unusual sensations, investigations, possible complications and permitted activities.
Below are answers to another 25 questions about knee replacements that patients search for online.
Contents
Why does my knee hurt at night?
What should I do if my knee hurts after a fall?
Why have numbness or pins and needles developed?
Why is fluid accumulating in the knee?
What does implant instability feel like?
How can implant loosening be recognised?
Can the implant shift out of position?
Can an infection develop around the implant?
When is revision surgery needed?
How long does the implant last?
Can I have an MRI?
Do I need regular X-rays?
What materials is the implant made from?
Which components make up the implant?
What does “total knee replacement” mean?
What is a unicompartmental knee replacement?
How is the implant fixed in place?
How much does the implant weigh?
Can both knees be replaced at the same time?
How long should I wear compression stockings?
Can I replace stockings with an elastic bandage?
How long will I need sick leave?
When can I swim?
Can I run with a knee replacement?
Can I drink alcohol?
Why does my knee hurt at night?
Night pain may reflect the tissues' response to daytime loading, continuing inflammation or an uncomfortable leg position. These sensations are fairly common early after surgery.
If pain increases, appears suddenly after a settled period or is accompanied by redness and marked swelling, contact a doctor.
What should I do if my knee hurts after a fall?
After a fall, stop putting weight on the leg and assess whether you can move it and bear weight. Severe pain, deformity, rapidly increasing swelling or inability to walk may indicate damage to bone or implant components.
An examination and X-ray are needed in this situation. Do not try to exercise the knee through pain on your own.
Why have numbness or pins and needles developed?
A small area of reduced sensation near the surgical scar may result from division of small skin nerve branches. This area often becomes less noticeable over time.
Spreading numbness, foot weakness, marked burning or loss of sensation require further assessment.
Why is fluid accumulating in the knee?
A reactive effusion may persist inside the joint after surgery: fluid produced in response to the procedure and loading. A small amount of fluid does not necessarily indicate a complication.
Repeated or rapid increases in knee swelling, especially with pain, redness or fever, require investigation. Joint aspiration is performed only when prescribed by a doctor.
What does implant instability feel like?
The patient may feel the knee giving way, shifting or failing to support body weight. Recurrent swelling and uncertainty when turning may accompany this.
Ligament condition, component position or other changes may be responsible. Examination and weight-bearing images are needed for diagnosis.
How can implant loosening be recognised?
Possible signs include gradually increasing pain when walking, pain at the start of movement and deterioration in knee function after a period of stable well-being.
Loosening can be confirmed only through investigation. The doctor assesses component position and compares new images with previous ones.
Can the implant shift out of position?
A correctly placed implant should not change position during normal daily activity. Displacement may occur after a serious injury, damage to surrounding bone or loss of component fixation.
Sudden pain, deformity or inability to bear weight require urgent medical attention.
Can an infection develop around the implant?
Infection can develop not only soon after surgery but also much later. Rarely, bacteria reach the implant through the bloodstream from another source of infection.
Signs may include increasing pain, swelling, redness, wound drainage and fever. Do not delay investigation of these symptoms.
When is revision surgery needed?
Another procedure may be needed for component loosening or wear, deep infection, marked instability or a fracture near the implant.
Pain alone does not mean that the implant must be replaced. The doctor first establishes the exact cause of the symptoms.
How long does the implant last?
Modern knee replacements often function for 15–20 years or longer. Longevity depends on age, body weight, loading, bone quality and implant type.
Elapsed time alone is not an indication for replacement. A stable, functioning implant does not require another operation.
Can I have an MRI?
A modern implant is not usually an absolute contraindication to MRI. Before the examination, tell the doctor and imaging staff about the metal implant.
Metal may interfere with images near the knee. Special MRI sequences or another diagnostic method may be used to examine this area.
Do I need regular X-rays?
Follow-up images help assess component position and surrounding bone. Some changes may develop before the patient feels pain or instability.
The surgeon sets the follow-up schedule. New symptoms may mean an X-ray is needed before the scheduled appointment.
What materials is the implant made from?
The main components are usually made from metal alloys, with a medical-grade polyethylene insert between them. Some designs use other modern coatings and materials.
Components are selected according to anatomy, bone quality and individual circumstances.
Which components make up the implant?
A total knee replacement includes femoral and tibial components, with a polyethylene insert between them. In some cases, the joint surface of the kneecap is also replaced.
The implant does not replace the whole leg or the entire knee: it replaces damaged joint surfaces.
What does “total knee replacement” mean?
Total knee replacement replaces the joint surfaces of the femur and tibia across all the main compartments of the knee.
“Total” describes the extent of joint surface replacement. It does not mean removing the whole knee together with its ligaments and muscles.
What is a unicompartmental knee replacement?
A unicompartmental implant replaces only one damaged compartment. The other compartments, ligaments and much of the patient's own tissue are preserved.
This option is not suitable for everyone. It is used for limited osteoarthritis when the other joint compartments and ligaments meet the necessary criteria.
How is the implant fixed in place?
Special bone cement is most often used in knee replacement to secure the components to the prepared bone.
Cementless implants are also available. The method is selected according to bone quality, implant model and the surgical plan.
How much does the implant weigh?
There is no single value: weight depends on component size and model. The patient does not usually perceive the implant as a separate heavy object.
A feeling of heaviness after surgery is more often related to swelling, muscle weakness or temporary changes in walking than to the implant's weight.
Can both knees be replaced at the same time?
Simultaneous replacement is possible for some patients, but it places greater overall demands on the body. Careful assessment of the heart, blood vessels and other organs is therefore needed.
In many cases, operations are performed one after the other. The choice between simultaneous and staged treatment is made individually.
How long should I wear compression stockings?
Duration depends on blood clot risk, mobility, other medical conditions and prescribed medicines. There is no single interval for all patients.
Stop wearing stockings according to the treating doctor's instructions, rather than only how you feel.
Can I replace stockings with an elastic bandage?
An elastic bandage provides appropriate compression only when applied correctly. A loose bandage will not have the required effect, while an overly tight one may impair circulation.
Do not replace prescribed stockings with a bandage on your own. Agree any substitution with your doctor.
How long will I need sick leave?
Duration depends on the work and individual recovery. Office work can usually be resumed sooner than physical work, prolonged standing or constant walking.
The treating doctor decides when sick leave can end after assessing knee condition and the ability to perform work duties safely.
When can I swim?
You may use a pool after complete wound healing. You must also be able to move confidently on wet surfaces and enter the water safely.
Start with gentle swimming without sudden movements. Discuss appropriate activity with the doctor beforehand.
Can I run with a knee replacement?
Running places repeated impact loads on the implant and surrounding bone. Walking, swimming, cycling and other lower-impact activities are therefore usually recommended.
Regular running and jumping may accelerate component wear. Any possible exceptions should be discussed individually with the surgeon.
Can I drink alcohol?
Alcohol can interact with pain medicines, anticoagulants, antibiotics and other drugs. It also impairs coordination and increases the chance of falling.
While medication continues, discuss alcohol with your doctor. Moderation also matters after medicines have been stopped.
A knee replacement is designed for long-term use and a return to active everyday life. It still requires sensible loading and periodic medical follow-up.
New or increasing pain, the knee giving way, rapidly increasing swelling, wound drainage or inability to bear weight are reasons to consult a specialist without waiting for the next scheduled appointment.
