Information about hip and knee replacements

What is a hip replacement?

A primary total hip replacement is an operation performed when the existing native joint is giving pain and decreased function of the hip, usually due to degenerative (osteoarthritis) or inflammatory arthritis of the hip.

The hip joint is a ‘ball and socket joint’; therefore a total hip replacement entails removing the original ball and socket, i.e. head and neck of femur (ball), as well as refashioning the acetabulum of the pelvis (socket). A synthetic implant is then inserted into both the femur and pelvis thus making the new joint.

This is performed to relieve the pain that the patient has been experiencing, and increase the function of the hip.

The X-ray above shows a right total hip replacement in-situ. The ball and socket of the original hip have been replaced with cemented implants. By comparison the left hip shows mild to moderate signs of osteoarthritis.

What can I expect from my hip replacement?

Hip replacements are successful operations. 95% of patients are satisfied with the outcome. The majority of people can achieve good results for many years, having complete relief or a significant reduction in their pain. The main reason for performing surgery is to reduce levels of pain, but your function (and quality of life) should be expected to improve.

However, your hip replacement may not last for the duration of your life and over the years it can wear out leading to increasing pain and instability in your hip. When this happens you may need to have the hip replacement revised. The vast majority of hip replacements are still in place and working well at 10 years following surgery - only around 5% of patients will have had further surgery to revise their hip by this stage, but in younger and more active patients this may be as high as 15%. A large proportion of patients (around 60% to 70%) who live for 20 years following their hip replacement will still have their original implant in place.

Recovery after hip replacement

Most patients are in hospital for 2-3 days following a hip replacement operation. You can expect to get up and about on the day of your operation, initially walking with a frame and then crutches or a stick. You can discard your walking aid at whatever point you feel comfortable to do so. Hip replacements are painful to recover from and you are likely to have wound pain for a few weeks following surgery. You should be determined and commitment to the rehabilitation programme to optimise your outcome.

By 6 weeks you should expect to be getting back to most of your day-to-day activities, including walking comfortably, driving and desk-based work. By 12 to 16 weeks you should be getting back to all the activities you wish to do, and there should be no restrictions at this point. Patients with heavy jobs could return to full activities if all is well at this stage. Studies have shown that patients continue to improve for up to 12 to 18 months following their hip replacement so if its taking you a bit longer than expected don’t get disheartened.

We recommend against impact activities (such as running, playing football and completive racquet sport games) but swimming and cycling are good for you and your hip replacement, and you should be encouraged to do these as soon as you feel able, usually after 4 to 6 weeks following surgery. Your local physiotherapy team will provide you with exercises to do, and you should carry on with these as you recover.

How do hip replacements fail?

Failure of hip replacements generally occurs either in the first year after surgery as a result of infection (where your hip replacements may need to be removed) or mechanical issues (such as recurrent dislocations), or many years after surgery, as a result of the components wearing out and causing loosening (which leads to pain and instability). Other problems leading to revision include a fracture around the implant or (rarely) ongoing pain.

What is a knee replacement?

Patients who have osteoarthritis of the knee experience pain and decreased function of the joint, which can negatively impact on their quality of life and impact on their ability to work. During a Total Knee Replacement procedure the worn out osteoarthritic knee is removed and replaced using metal and plastic replacement.

The knee joint is comprised of the bottom end of the femur (in the thigh) and the upper end of the tibia (in the lower leg). In a total knee replacement both of these pieces of bone are completely removed, as well as some of the soft tissue in-between. In a partial or unicompartmental knee replacement only part of these pieces of bone are removed, as well as some of the soft tissue in-between.

In place of the native knee, metallic implants are cemented onto the cut surfaces of both the femur and tibia, with a highly durable plastic liner placed in between these keeping the two metal surfaces apart.

The X-ray above shows a left total knee replacement in-situ. The lower end of the femur and the upper end of the tibia have both been replaced by cemented implants, with a plastic liner lying in between these. By comparison the right knee (image on the left) shows evidence of osteoarthritis.

What can I expect from my knee replacement?

Knee replacements are successful operations and 85% (17 out of every 20) of patients are satisfied with the outcome. The majority of people can achieve good results for many years, having complete relief or a significant reduction in their pain. The main reason for performing surgery is to reduce levels of pain, but your function (and quality of life) should also be expected to improve. Unfortunately 10% (1 in 20) of patients may not be happy with their knee replacement. The reasons for this are not always clear but may be related to ongoing pain, stiffness, instability or a failure of the knee to do what the patient hoped it would.

Your knee replacement may not last for the duration of your life and over the years it can wear out leading to increasing pain and instability in your knee. When this happens you may need to have the knee replacement revised. The vast majority of knee replacements are still in place and working well at 10 years following surgery - only around 5-10% of patients will have had further surgery to revise their knee by this stage, but in younger and more active patients this may be as high as 15%. A large proportion of patients (around 60% to 70%) who live for 20 years following their knee replacement will still have their original implant in place.

Knee replacement types

Almost all knee replacements performed by the South Tees hip replacement team are ‘cemented’ total knee replacements. A total knee replacement involves replacing the worn bone on both the inside and outside of the joint between the bottom of your thigh bone (Femur) and the top of your shin bone (Tibia). The surgeon may also choose to replace the bone on the back of your knee cap; this decision is usually made during the operation. In England and Wales about 1 in every 3 people have this done, meaning 2 in every 3 do not require anything to be done to the knee cap.

Some patients may be offered a ‘partial’ knee replacement. Partial means only part of the knee is replaced, either the inside of the knee, the outside of the knee or just the knee cap joint. This is only suitable for those patients who have osteoarthritis (wear and tear) limited to one area of the knee. These partial knee replacements have a higher rate of failure than a total knee replacement and evidence of better relief of symptoms or restoration of function when compared to total knee replacement is limited.

How do knee replacements fail?

Failure of knee replacements generally occurs either in the first year after surgery as a result of infection (where your knee replacement may need to be removed) or many years after surgery, as a result of the components wearing out and causing loosening (which leads to pain and instability). Other problems leading to revision include a fracture around the implant or (rarely) on-going pain.