Normal pain versus warning signs after knee replacement

Go to the emergency department or call 108 now if you notice these

Some symptoms after knee replacement need immediate care. Go to the nearest emergency department or call 108 for an ambulance if you suddenly feel breathless or have chest pain. These can be signs of a blood clot that has travelled to the lungs. Do not drive yourself; ask someone to drive you or call 108. Bring any medicines you are taking with you.

Call 108 or go to the emergency department if you have severe pain and swelling in your leg and you are having difficulty breathing or chest pains. This combination of symptoms is a medical emergency. If you are alone and cannot reach a phone, ask a neighbour or passer-by to call for you.

Sudden inability to move your foot or a cold, pale, or blue foot also needs emergency care. These can mean a blocked blood vessel. Do not wait to see if it improves. Call 108 straight away.

What normal pain and swelling look like in the first weeks

After knee replacement, it is normal to have pain around the operated knee and along the shin and thigh bones. You will feel pain from the surgery itself and as the body heals. Most people have pain and discomfort for a few weeks, which improves over time. Night pain that affects sleep is common, and very few people sleep through the night at six weeks.

Swelling of the operated knee, calf, and ankle is normal. Swelling often increases in the first few days after surgery. It may take a few months to fully resolve and can be managed with regular ice, elevation, and keeping active. Apply ice packs for no longer than 20 minutes at a time after exercise.

Bruising may appear around the knee, track down to the ankle, or show in the thigh. A numb area on the outer side of the knee is normal due to the incision and may remain permanently in a small patch. Weakness is expected and it takes a few months to build muscle strength and confidence. Take pain relief regularly so you can move and do your exercises.

Most people have pain and discomfort for a few weeks, which improves over time.

Wound healing: normal changes versus signs of infection

Mild redness, warmth, and a small amount of wound ooze are normal parts of healing. The wound is usually closed with metal clips that are removed after about two weeks. Some heat around the new joint can be expected.

Contact your care team if:

• The dressing leaks blood or fluid
• The area becomes increasingly hot and painful
• The wound looks open
• Or you develop a fever and feel unwell

Spreading redness, increasing heat, persistent leakage, or a high temperature with flu-like symptoms and redness around the wound are signs that need same-day assessment. A wound infection is usually treated with antibiotics. If the infection spreads deep into the joint, further surgery may be needed.

Calf symptoms that may mean a blood clot

A blood clot in the leg (deep vein thrombosis) is a known risk after knee replacement because of how blood flows and clots after surgery.

Symptoms include throbbing or cramping pain in the calf, behind the knee, in the thigh or in the groin.

Swelling in one leg, warmth, redness or darkening of the skin, and swollen veins that are tender to touch are also warning signs.

If you notice any one of these symptoms, contact your care team or go to the emergency department the same day. A clot can move to the lungs and become life-threatening.

To reduce the risk, your doctor may suggest compression stockings or anticoagulant medicines. Wear stockings as advised and tell the team if they feel too tight or leave deep red marks. Keep moving within your limits and do your prescribed exercises. If you are unsure whether your calf symptoms are normal, call the hospital ward for advice.

Sudden giving-way, loud clicks or new instability

It is normal to feel some weakness in the leg for a few months after surgery as the muscles rebuild strength. A sudden buckle or the knee giving way when you put weight on it is different from general weakness and may mean the joint is unstable.

A loud click or pop that comes with pain or a feeling that the knee has moved out of place should be checked promptly. If you cannot bear weight on the leg at all, do not force it; ask someone to help you sit down and keep the leg elevated.

These mechanical symptoms can happen if:

• A ligament is stretched
• If the joint surfaces are not tracking smoothly
• Or if there is a loose fragment inside the knee

They are not an emergency unless the knee looks deformed, the leg is numb or cold, or you have severe pain that does not settle with rest and your usual pain relief. In those cases, go to the nearest emergency department or call 108 for an ambulance.

For a giving-way episode without those emergency signs, contact your surgeon or the hospital ward the same day. They will decide whether you need an earlier clinic review, an X-ray, or a change in your physiotherapy plan. Until you are seen, use your walking aid for every step and avoid twisting or pivoting on the operated leg.

Fever and painkillers: what to do if you feel unwell

A temperature of 38°C or higher after knee replacement can be a sign of wound infection or a deeper joint infection. If you have a fever together with increasing redness, heat or ooze from the wound, or if you feel hot, cold or shivery, contact the hospital ward or your surgeon straight away. Do not wait to see if it settles.

Keep taking your regular pain relief unless your doctor has told you to stop a specific medicine. Stopping painkillers suddenly can make it harder to move and do your exercises, which slows recovery.

If you are unsure whether a particular tablet is safe with a fever — for example, if you are on blood-thinning medication — phone the ward or your doctor’s office for advice before you take the next dose.

If you have been prescribed stronger pain medication, continue it as directed and tell the care team about the fever when you call. Bring a list of all your medicines with you if you are asked to attend the hospital.

When to contact your surgeon or the hospital ward

Call the ward or your surgeon’s office during working hours if pain is getting worse despite regular pain relief, ice and elevation. Increasing swelling that does not improve with rest and leg elevation, or new swelling that appears weeks after surgery, should also be reported.

Wound concerns that need a same-day call include:

• Dressing leaking blood or fluid
• The wound edges gaping open
• Spreading redness or heat around the incision
• Or persistent ooze that does not stop after a fresh dressing

Numbness that spreads beyond the small patch on the outer knee, or a change in colour or temperature of the foot, should be mentioned immediately.

If you feel you are not progressing — for example, you cannot bend the knee further after several weeks, walking distance is not improving, or you are struggling with the exercises — ask for a review. The typical follow-up is around six weeks, but you do not have to wait for that appointment if something feels wrong. Keep the hospital’s ward number handy and have your discharge summary or medication list ready when you call.