Unfortunately, this is something we hear in 10-15% of patients after they have had a knee replacement, which they had hoped was going to relieve them of all their knee symptoms. The big question is what can be done about it and perhaps more importantly, what should be done and what should not be done. Our patients are always told before surgery that the outcomes are not all perfect, but it is not what you want to hear and most people think that that will only happen to someone else. If you are unlucky enough to be in the group that have persistent symptoms, your surgery will not have met your expectations and you will be hopeful that someone can put it right for you. Bear in mind that full recovery from a knee replacement may take 12-18 months to happen, so try to be patient.
Figure 1 shows an X-ray of right total knee replacement and a left medial partial knee replacement.
Having been in consultant practice as a knee surgeon and surgical trainer for 24 years, I am often asked to give a second opinion. As a result, perhaps the most challenging group of patients I see are patients who are dissatisfied with the outcome of their knee replacement surgery. So here’s what I do…
Firstly, there is no rush. I need to hear your story right from the beginning. What were the symptoms that led to you opting to have a knee replacement in the first place? How long had they progressed over? What else had been tried in terms of treatment? How did the surgery and immediate post-operative period go? What has happened to the pain since? Is it the same pain of different? etc. etc. I need to know what surgery was done, who did it, where and when. Preferably I would like the operation notes and the x-rays and scans that were done before and after surgery. The full story often points to the cause more than the subsequent examination and investigations. This takes time – you need to tell your story and I need to hear it.
Secondly, I will carry out an examination of your knee, observing the way you walk and function on it and carefully assess both your hips and lower back as both are known to give knee pain known as “referred pain”. This could have been the cause of your pain all along or could have developed since surgery.
Thirdly, I will review the investigations that have already been done and decide whether any new investigations are needed. These may be blood tests, plain x-rays, CT scans, MRI scans or occasionally an isotope bone scan (an injection of a weakly radioactive substance that is taken up by bone and picked up in a scanner). Thus it may be that you go off to have these investigations and we meet for a follow-up appointment to discuss the results.
If I can find a definite cause for your pain, it will point me in the right direction to treat you with some chance of success. It is much harder if i do not find a specific cause for your persistent pain. If your muscle strength is poor and if your gait pattern is poor as a result, some well guided rehabilitation with a quality physiotherapist maybe all you will need to get the full benefit from your surgery.
Broadly speaking, there are four reasons why I would consider doing further surgery:-
To diagnose and/or treat infection.
To correct something that is in the wrong position (malalignment or malpositioning).
To manage instability of the knee.
To correct a component that has become loose or excessively worn.
Deep infection complicates about 1-2% of knee replacements and is the complication surgeons most fear. We take a number of actions in primary surgery to prevent it happening but whatever we do, there is still a risk. Infection may present itself acutely (in the first weeks or months following surgery). These are usually obvious and are caused by the bacteria that cause most acute infections elsewhere in the body and need aggressive early treatment. The more indolent, chronic grumbling infection is less obvious but remains one of the causes of a poor result from surgery. Bacteria that do not usually cause acute infection, many of which reside on or in our bodies all the time causing us no harm, can “infect” artificial joints. This infection causes pain and sometimes stiffness of the joint. The bacteria form a film on the metal and plastic components out of reach of our own immune systems and of any antibiotics. They will usually, but not always, promote an inflammatory response that we can pick up on blood tests. Sometimes there will have been a minor problem with the early healing of the surgical wound which allows the bacteria access to the joint.
To confirm or refute infection as the cause, we may aspirate your joint (draw fluid off with a needle) or carry out an arthroscopy and biopsy of the joint (keyhole surgery under general anaesthetic). If we grow bacteria, we have a positive diagnosis. If we do not, we have evidence against it being the cause but cannot categorically say that it is negative.
If infection is confirmed, I will discuss the options for treating this, which may involve suppressive but not curative antibiotic treatment but may involve complex revision surgery to cure it.
If the investigations show something definitely out of position or incorrectly placed, I can discuss with you what options there are for correcting that and the likely chances of success. It may be that small adjustments can be made. It may be that only a full revision is the option.
Whilst the surgery in knee replacement is carried out on the bones, it is the soft tissues that make the knee work – the muscles, tendons and ligaments. If the soft tissues are deficient or the “balance” of them is wrong, you may suffer from true instability of the joint. Again the options for treatment can be discussed.
Knee replacements come in two broad types. Some are cemented into the bone and some rely on bony ingrowth to fix them to your bones (uncemented). Loss of fixation and/or wear of the plastic or metal components are the most common causes of failure of knee replacement in the longer term, but sometimes we see a component becoming loose much earlier. This may be due to poor fixation or possibly due to uncommonly high forces being applied to it. The forces that go through your knee on a daily basis are related to your weight, degree of activity and coordination of muscle control. A minor malpositioning of your components may lead to earlier failure whereas larger errors of positioning will lead to earlier failure for the same reasons. This is the commonest reason overall for revision knee replacement surgery. The diagnosis is made on x-rays and/or CT or isotope scans mentioned above.
Figure 2 shows a sound left total knee replacement and a grossly loose right total knee replacement. Don’t worry, they don’t all look this bad!
Figure 3 shows a revision total knee replacement – you will see the metal components are much bigger and extend further down the bone to get solid fixation.
If you do not have evidence of any of these four things (infection, malalignment, instability or loosening), you are unlikely to be helped by further surgery. If we find a cause for your pain away from your knee, such as your hip or lower back we can treat these. However, we are left with a group of patients in whom we are unable to explain the persistent pain. This is especially true in those patients in whom the initial pre-operative pain that led to the surgery is still present after the surgery. In these cases, perhaps the arthritis was not the cause of the pain in the first place but we were unable to find another cause? I do not have any magic answers for this group. We sometimes have to accept that the result of the primary surgery is poor. Further surgery is likely to result in a worse result and should be avoided. I often refer these cases to a specialist pain clinic service but also tend to keep you under review with me with regular x-rays in case we do pick up subtle signs of loosening of the components that puts you into one of the four groups above.
When deciding whether to have revision surgery done, it is prudent to remember that whilst revision surgery has a good success rate when done for the right reasons, it is major surgery and the risks of complications following revision surgery are higher than they were the first time round regardless of the indication for the re-do surgery. It is not a decision to undertake lightly. Be sure to understand the consequences of not undergoing surgery as well as those of undergoing surgery when making your decision. We are here to help you with that decision but the final decision is always yours.
Richard Dodds OBE FRCS Orth.
Consultant Orthopaedic Surgeon
Reading Hip and Knee Unit
31st July 2018.