Joint Replacement Surgery (Hip/Knee)

Joint replacement surgery is an operation in which a damaged hip or knee joint is removed and replaced with an artificial joint, called a prosthesis, made from metal, ceramic, or strong plastic.

In a healthy joint, smooth cartilage (the slippery tissue that covers the ends of bones) lets the bones glide past each other without pain. When that cartilage wears away or is destroyed by disease, the raw bone surfaces grind together, causing severe pain and stiffness. During the operation, the surgeon removes these damaged surfaces and fixes a prosthesis in their place. The prosthesis recreates the smooth, rounded shape of the original joint so the bones can move again without grinding.

Joint replacement is considered when the hip or knee joint has been so severely damaged that pain and loss of movement cannot be controlled by other means. The most common reason is advanced osteoarthritis (a condition where joint cartilage gradually breaks down), but several other conditions can also lead to the same level of damage.

• Osteoarthritis (cartilage breakdown due to age or long-term wear) that no longer responds to physiotherapy or pain medication
• Rheumatoid arthritis (an autoimmune disease that attacks the joints) causing severe joint destruction
• Post-traumatic arthritis — joint damage that developed after a fracture (broken bone) or serious injury
• Avascular necrosis (bone death caused by poor blood supply to the joint) in the hip
• Severe hip fracture in older adults where repair alone is unlikely to restore function
• Bone tumours affecting the hip or knee joint, in selected cases

This surgery is not suitable for everyone. A surgeon will usually advise against it in certain situations.

• Active infection anywhere in the body, including in the joint itself — surgery is typically postponed until the infection is fully treated
• Severe medical conditions (such as uncontrolled heart disease) that make a long operation under anaesthesia too dangerous
• Very young, highly active patients in some cases, because prostheses have a limited lifespan and may need to be replaced again later
• Severe obesity that significantly increases the risk of complications — weight loss may be recommended first
• Poor bone quality that cannot hold the prosthesis securely in place

Joint replacement is a well-established operation, but like any major surgery it carries recognised risks that your surgical team will discuss with you beforehand.

• Deep vein thrombosis or DVT (blood clots forming in the leg veins) — one of the most common concerns after this surgery; blood thinners and early movement are used to reduce this risk
• Pulmonary embolism (a blood clot that travels to the lungs) — a serious but less common complication
• Surgical site infection, either in the skin wound or, more rarely, deep around the prosthesis
• Prosthesis loosening — the artificial joint gradually becomes less firmly fixed to the bone over years
• Dislocation — the ball-and-socket components of a hip replacement can shift out of position, particularly in the early weeks after surgery
• Leg-length difference — in hip replacement, one leg may be slightly longer or shorter than the other after the procedure
• Nerve or blood vessel injury near the joint, causing numbness, weakness, or, rarely, reduced circulation
• Stiffness or limited range of motion in the replaced joint despite physiotherapy
• Wear of the prosthesis components over time, which may eventually require a revision (repeat) operation
• General anaesthesia risks, including breathing difficulties and reactions to anaesthetic medicines
• Delayed wound healing, particularly in patients with diabetes or those who smoke

Good preparation helps reduce complications and supports a smoother recovery. In the weeks before surgery, the medical team will give specific instructions, but there are several things that are typically expected of the patient.

Lifestyle adjustments before surgery usually include stopping smoking as early as possible, since smoking slows wound healing and raises infection risk. Alcohol is usually restricted in the days leading up to the operation. If the patient takes blood thinners, anti-inflammatory medicines, or certain supplements, the doctor will advise on which to pause and for how long. Patients with diabetes will have their blood sugar monitored carefully in the run-up to surgery.

Fasting requirements are given by the anaesthesia team. In most hospitals, patients are asked to stop eating solid food several hours before the operation and to stop drinking even clear fluids a shorter period before. The exact times vary, so the team's written instructions should be followed carefully.

Before the operation date, a number of tests are usually ordered to make sure the patient is safe to have surgery under general or spinal anaesthesia (anaesthesia injected into the spine to numb the lower body). These commonly include:

• Blood tests to check for anaemia (low red blood cell count), kidney function, blood clotting, and blood sugar
• ECG (electrocardiogram) to assess heart rhythm
• Chest X-ray to check the heart and lungs
• X-rays of the affected hip or knee to plan the size and fit of the prosthesis
• Blood pressure measurement and general physical examination
• Urine test to rule out a urinary infection before surgery

On the day of surgery, the typical sequence of steps is as follows, though the exact order can vary between hospitals:

• 1. The patient is admitted and identity and consent forms are confirmed.
• 2. A nurse prepares the skin over the joint — this usually involves cleaning and sometimes shaving the area.
• 3. An intravenous (IV) line is placed in the arm to deliver fluids and medicines during surgery.
• 4. The anaesthesia team administers either general anaesthesia (the patient is fully asleep) or spinal anaesthesia (the lower body is numbed while the patient remains awake or lightly sedated).
• 5. Antibiotics are given through the IV line just before the incision (cut) is made, to reduce infection risk.
• 6. The surgeon makes an incision over the hip or knee, moves aside the surrounding muscles, and exposes the damaged joint.
• 7. The damaged bone and cartilage surfaces are carefully removed using surgical instruments.
• 8. The prosthesis components are shaped, fitted, and fixed to the prepared bone — either with bone cement or by pressing them firmly so bone grows into them over time.
• 9. The joint is tested through its full range of motion to confirm stability.
• 10. The incision is closed in layers with stitches or staples, and a dressing is applied.
• 11. The patient is moved to the recovery room to wake up and be monitored.

Recovery from joint replacement takes place in stages — from the hospital ward, to home, to gradual return to normal activity. Most patients stay in hospital for several days, though the exact length depends on how the recovery progresses and the type of joint replaced. During the hospital stay, nurses monitor for early complications such as blood clots, infection, and unusual pain. A physiotherapist (a specialist in movement and rehabilitation) usually begins gentle exercises within a day or two of surgery — early movement is important to prevent blood clots and to help the joint begin working again.

• Pain management: the team will manage pain with appropriate medicines in the days after surgery; patients are encouraged to report pain honestly so it can be controlled well
• Blood clot prevention: blood thinners and compression stockings (tight socks that squeeze the leg to keep blood moving) are typically used for several weeks after surgery
• Wound care: the surgical wound is kept clean and dry; dressings are changed according to the hospital's schedule, and any signs of infection — increased redness, warmth, swelling, or discharge — should be reported immediately
• Weight-bearing: how much weight can be put through the operated leg varies; the physiotherapist will guide the patient on using walking aids such as crutches or a walking frame
• Hip dislocation precautions (for hip replacement): patients are usually advised to avoid certain positions — such as crossing the legs, bending the hip past a right angle, or twisting — for several weeks while the soft tissue heals around the new joint
• Physiotherapy at home: exercises given by the physiotherapist need to be continued after discharge; in many cases, outpatient physiotherapy sessions are arranged
• Follow-up appointments: the surgeon will schedule check-ups to examine the wound, review X-rays of the new joint, and monitor progress — these are usually at a few weeks, then a few months after surgery
• Return to driving: this is only permitted once the operated leg has enough strength and reaction speed; the surgeon will advise on timing
• Return to work: desk-based work may be possible after several weeks; physical jobs that involve standing, walking, or lifting take considerably longer
• Long-term care of the prosthesis: patients are advised to tell any future doctor or dentist about their joint replacement, as some medical and dental procedures require antibiotics beforehand to protect the artificial joint from infection
• Lifestyle: maintaining a healthy weight reduces stress on the new joint; high-impact activities such as running or jumping are usually discouraged long-term to reduce wear on the prosthesis