Knee Fracture / Injury

Introduction

Total knee replacement is a common operation to replace a knee joint that is damaged or worn away (usually by arthritis or injury) with an artificial one. It’s a good option if the pain cannot be controlled with other methods such as physiotherapy or pain killers.

Knee anatomy

The knee joint is like a hinge and is made up of three parts which include the thigh bone (femur), shin bone (tibia) and kneecap (patella). Where the bones meet they are covered in a hard, slippery material called cartilage that helps them slide over each other easily but if the cartilage is damaged by injury or worn away by arthritis, for example, it can make the joint painful and stiff.

Prosthetic knees

A new knee joint is made of metal and plastic and can last for up to 20 years.

It’s also possible to have a partial knee replacement which resurfaces only the inner or outer half of the knee but this is only suitable for people with arthritis in one half of the knee. Total knee replacements are more common.

Surgical procedure

The operation itself usually takes up to two hours under general anaesthesia so that the patient is unconscious. It’s also possible to have the surgery under spinal or epidural anaesthesia in which all feeling from the waist down is blocked.

The procedure itself starts with a single cut (10 to 30cm long) down the front of the knee. This exposes the kneecap which is moved to one side to reach the knee joint. Mr Hull then removes worn and damaged bone and cartilage from both the end of the thigh bone and the top of the shin bone. The surfaces of these bones are shaped to fit the artificial knee joint.

A metal and plastic knee replacement implant is then attached to function as a new knee joint. Depending on the condition of the cartilage underneath the kneecap, Mr Hull may also replace the kneecap surface with a plastic part. This is called patellar resurfacing.

Mr Hull uses the cemented Genesis II knee replacement from Smith and Nephew.  This is a well proven knee replacement, with excellent long term results (UK national joint registry shows only 2% of Genesis II knees required revision at 7 years, some of the best results available - View)

Mr Hull will then close the wound with stitches or clips and cover it with a dressing. The knee is also tightly bandaged to help minimise swelling.

Risks and complications

It’s good to be aware that there can be complications with this surgery, although serious ones are rare. As with all operations, there is a possibility of a reaction to the anaesthetic, excessive bleeding, developing a blood clot and wound infection. A general anaesthetic may also make you feel temporarily sick after the operation.

Specific to knee replacements, there’s a small chance of infection around the prosthesis and sometimes this requires another operation to clean out the knee. Blood clots are another possibility, especially given that you won’t be able to move around much at first. To help prevent this, we will give you blood thinners.

Other less common concerns which nevertheless you need to be mindful about include pieces of fat in the bone marrow becoming loose, which can subsequently enter the bloodstream and get into the lungs, potentially causing serious breathing problems.

Nerves in the knee area may also be injured from swelling or pressure and can cause some numbness.  It is common that there is a small patch of numbness on the outside of the shin bone after surgery.

Occasionally following surgery the knee replacement becomes very stiff, necessitating another small operation to improve the range of motion.

In the long term the knee replacement may wear out, requiring the surgery to be redone.  This is an especially important consideration for younger patients.

Preparing for surgery

Mr Hull will talk to you about how best to prepare for surgery which may include stopping taking any anti-inflammatory medications such as aspirin to reduce the risk of blood clots and stopping smoking if you are a smoker to minimize the risk of infection.

If you're having a general anaesthetic, you will be asked to follow fasting instructions. This means not eating or drinking, typically for about six hours beforehand.

Mr Hull may also ask you to wear compression stockings to help prevent blood clots forming in the veins in your legs.

Recovery

After the operation, you will need to rest until the effects of the anaesthetic have worn off. You may not be able to feel or move your legs for several hours after a spinal or epidural anaesthetic.

You may need some pain relief to help with any discomfort and it is also likely that we will give you an injection into your abdomen to help prevent blood clots forming in your legs, and possibly a short course of antibiotics to help prevent infection.

Our physiotherapist will also guide you daily about how to exercise to aid your recovery, exercises which you must continue for about two months when back at home.

Normally patients need to stay in hospital for about three to five days following surgery. Once at home, it should be possible to walk around and even manage the stairs with the help of walking aids such as crutches or a stick for the first few weeks. It’s also important to raise the leg and support the knee when sitting down to help prevent swelling in the leg and ankle.

You’ll probably be able to go back to work after six to 12 weeks, as long as the work isn’t too active and doesn’t exert the knee. Driving is best left until you can comfortably perform an emergency stop and certainly for at least 6 weeks.

Further information

For further information please contact Mr Peter Hull FRCS, Consultant Trauma & Orthopaedic Surgeon.