What happens during knee replacement surgery? A step-by-step guide

Knee replacement surgery is one of the most common and effective procedures for treating severe knee pain, particularly caused by arthritis. Many patients understandably feel anxious about what actually happens during the operation.

In this guide, consultant orthopaedic knee surgeon Mr Aadil Mumith outlines what to expect during knee replacement surgery, from admission to the operating theatre through to the completion of the procedure.

Before the operation: preparation and anaesthesia

On the day of surgery, patients are admitted to hospital and assessed by the surgical and anaesthetic teams. The knee to be operated on is marked, and final safety checks are completed.

Most knee replacement procedures are performed under either spinal anaesthesia (the patient is awake but numb from the waist down) or general anaesthesia (the patient is fully asleep). A nerve block is often used to help control pain after surgery.

Step 1: positioning and sterile preparation

In the operating theatre, the patient is positioned comfortably on their back. The knee is cleaned thoroughly with antiseptic solution, and sterile drapes are placed to maintain a clean surgical environment and reduce the risk of infection.

Step 2: making the incision

A straight incision is made over the front of the knee to allow access to the joint. The underlying tissues are carefully moved aside to expose the damaged surfaces of the knee.

Step 3: removing damaged bone and cartilage

The worn cartilage and a small amount of underlying bone are precisely removed from:

• The end of the thigh bone (femur).
• The top of the shin bone (tibia).
• Sometimes the back of the kneecap (patella).

Specialised instruments are used to ensure accuracy, alignment, and balance of the joint.

Step 4: placing the knee replacement components

The artificial joint, known as a knee implant, is then fitted into place. It typically consists of:

• A metal component attached to the femur.
• A metal baseplate on the tibia.
• A smooth plastic insert between them to allow movement.

These components may be fixed using surgical cement or designed to bond naturally with the bone over time.

Step 5: checking movement and stability

Before closing the wound, the surgeon carefully checks that the knee moves smoothly, remains stable throughout its range of motion, and is correctly aligned. Any necessary adjustments are made at this stage to optimise the function and longevity of the knee replacement.

Step 6: closing the wound

The incision is closed in layers using stitches or clips. A sterile dressing is applied, and in some cases, a drain is used temporarily to remove excess fluid.

After the procedure: recovery begins

Following knee replacement surgery, patients are taken to the recovery area where they are closely monitored. Most begin gentle movement and physiotherapy on the same day or the following day, which is essential for recovery.

Knee replacement surgery is a precise and well-established procedure designed to relieve pain and restore mobility. With modern surgical techniques and structured rehabilitation, most patients experience excellent outcomes and a significant improvement in quality of life.