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How old is too Young for Hip and knee arthroplasty

Nearly every day I consult I would see a patient in their 40's or early 50's with bone on bone arthritis of the knee and less commonly the hip.

Unfortunately, the easiest operation for me to perform on these patients is a total joint replacement (Arthroplasty). Why?- Because the surgery has predictable results including pain relief.

However, is this the morally, ethically and scientifically the right thing to do?

The answer is very complex. My longest consultations are with these patients. I need to spend a long time explaining to them what their options are.

1. Non Operative

  • Analgesia
  • Weight Loss (A medical issue in itself which has shown to increase the risk of developing osteoarthritis in these younger patients)
  • Activity Modification
  • Alternate therapy – Physio, acupuncture, massage therapy etc.

2. Operative

  • Salvage non-arthroplasty options e.g. HTO (realignment surgery) for the knee, which shifts the weight to the outside of the knee, thus preserving the inside of the knee for as long as possible.
  • Arthroscopy clean out (Research is now proving that this is not acceptable practice)
  • Minimally invasive bone preserving Arthroplasty e.g. UKR (half a knee replacement)

The last option is a Total Knee Replacement. (Replacement of all 3 compartments – inside, outside and the front of the knee)

So How Old is too young?

The youngest patient I have done knee replacement is 42 yrs. old. He was an electrician working on the windmills out west. He had a family and was the sole income earner. He came to see me with severe deformity (bent) knees, pain, swelling and stiffness. He had pain was able to deal with it (Bushy- she’ll be right mate). Functionally, he could not climb the ladder to get up the windmill and was feeling very unstable and could possibly fall over.

He was about to lose his livelihood. He was going to lose his house and family. In this case, we had no option but to proceed with total knee replacement surgery.

I also have an anecdote of patients in their 40’s to early 50’s whom I see with mild, early arthritis but want to run marathons, or are overweight or refuse to take analgesia. Essentially these patients need to optimise their function and make a few lifestyle changes to avoid Knee or Hip replacement surgery.

Why not replacement??

As I mentioned, I would love to perform hip and knee replacements all day, every day. I have some amazing state of the art equipment to utilise with and the results are terrific in the short to medium term. But what about the long-term? The need for further revision is required when the patient would be in their 60’s to 70’s, and there is only so much bone that can be removed before there are no options left.


A person in mid 60’s will be 75-80 years of age before his/her knee wears out. If you have followed my previous post – I have to resect some of your bone (not much with navigation technique) to replace it with metal and plastic.


There are 2 issues here-

  1. I have taken some of your bone away
  2. I have put plastic (soft) material between chrome cobalt and titanium.

So as you move the knee and since you are young, you will move it a lot more than a 65-70-year-old. As you move the plastic undergoes a wear process and releases very minute plastic particles in the knee joint. These particles have nowhere to go. However, the body detects that there is something foreign in the knee joint floating around. It sends its soldiers, the white cells to fight this foreign enemy. Usually, this foreign enemy is either virus or bacteria and the usually this war is won by the body.

This time the enemy is non-biological. The white cells in an attempt to kill the plastic will ingest (engulf) it but are unable to kill it and it the process the white cell releases all the toxic enzymes as it dies into the knee joint. These enzymes really have no effect on the metal or the plastic but it now starts to dissolve the bone behind the knee replacement and so the knee comes loose and the patient starts developing pain again.


This leads to revision knee replacement. The surgery is then repeated and the process starts all over again. If there is an active infection, sometimes this surgery takes place in two stages over a period of 6 – 12 months.

If you are 65, your knee may last 10-15yrs. If you are 45, it will last for 5-10 yrs. This is directly related to the activity level of a 45 year. old when compared to a 65-75-year-old.

At some stage, there won’t be enough native bone to fix the revision knee into. This is a catastrophic disaster. The only option is a Tumor Prosthesis, which is not ideal and not indicated for the young.

I hope I have given some food for thought for the young arthritis sufferers. Have a good think about your options. If your life is an absolute misery, and you are about to lose your livelihood because of your hip or knee pain, then replacement is an option for you as well. You must understand the consequences of your decision (In collaboration with your surgeon).