People come to this appointment expecting to be told. They expect a threshold: a grade on the X-ray, a pain score, an age, a point at which the answer flips from no to yes. There is no such threshold, and any surgeon who implies otherwise is simplifying.
It is not the X-ray.
The X-ray establishes what the structure is doing. It does not establish what should be done about it. A systematic review of the literature found substantial discordance in both directions: a large proportion of people with clear radiographic osteoarthritis have no knee pain, and a substantial proportion of people with painful knees have unremarkable films.1
So a bone-on-bone X-ray in someone who walks the dog every day and sleeps through the night is not an indication to operate. And a moderate X-ray in someone who has stopped leaving the house may well be. Reading your knee X-ray sets out what the film does and does not show.
What the decision actually rests on.
Four things, weighed together rather than scored.
What you have stopped doing. This is the most useful single question in the consultation, and it is more informative than any pain scale. Not what hurts, but what you no longer do because of it. The person who has stopped bowls, stopped the beach walk, stopped going upstairs to their own bedroom, is describing something a number cannot.
Night pain. Pain that reliably wakes you, or stops you getting to sleep, is one of the more meaningful symptoms in knee arthritis. It tends to be a late-stage feature and it responds well to replacement.
What has already been tried, and for how long. A knee replacement is appropriate when non-operative treatment has been tried properly and has stopped working. Properly means a supervised strengthening programme for at least three months, not a handout and good intentions. See what to try before knee surgery, and injections and other procedures for where those fit.
Whether the operation can deliver what you want from it. This is where expectations get examined. A knee replacement reliably relieves arthritic pain. It does not produce a normal knee, it does not restore full flexion in most people, and it is a poor operation for someone whose main complaint does not come from the arthritis.
Why there is almost never urgency.
Knee arthritis is not dangerous. Waiting does not damage the knee in a way that makes the operation harder or the result worse, within reason. That means the timing is genuinely yours: around work, around a wedding, around the cricket season, around a carer's availability.
The qualification is the phrase "within reason". Waiting until you can barely walk has a cost, and it is not the knee. It is you. People who wait until they are housebound arrive deconditioned, with wasted quadriceps, a stiff joint and often weight gained during the years they stopped moving, and every one of those makes the recovery harder and the ceiling lower. Poorer function before surgery predicts poorer function after it.
So the honest framing is not "wait as long as you can". It is "wait as long as it is worth waiting", which is a judgement about your life rather than about your knee.
What being too early looks like.
There are patterns where the answer is not yet, and they are worth naming because they are common.
- Pain that does not match the imaging, which usually means the pain is coming from somewhere else. The hip, the lumbar spine and the patellofemoral joint all refer to places people call "the knee".
- Symptoms that have never been treated. A knee that has had no strengthening, no load management and no analgesia trial has not yet been treated.
- Wear confined to one compartment in someone young and active, where a partial knee replacement or a referral for an osteotomy may be the better answer. Professor Rodda does not perform osteotomy, and where that is the right operation the referral goes to a colleague who does.
- Expectations the operation cannot meet, most often about kneeling, or about returning to running.
How it is decided in the room.
Not by Professor Rodda alone, and not by you alone. The surgeon's job is to establish whether the operation is technically appropriate, what it would realistically achieve for you, and what the risks are in your particular case. Your job is to decide whether that trade is worth making, and it is a legitimate answer to say not yet.
People come back. A decision to wait is not a decision to be discharged, and the question is revisited whenever your answer to "what have you stopped doing" changes. The Oxford Knee Score is useful here precisely because repeating it in six or twelve months shows you which direction you are moving in, which a single consultation cannot.
References.
- Bedson J, Croft PR. The discordance between clinical and radiographic knee osteoarthritis: a systematic search and summary of the literature. BMC Musculoskelet Disord. 2008;9:116.
- Australian Orthopaedic Association National Joint Replacement Registry. Hip, Knee & Shoulder Arthroplasty Annual Report. Adelaide: AOA.
Common questions.
Does bone on bone mean I need a knee replacement?
No. The X-ray describes the structure, not what should be done about it. A large proportion of people with clear radiographic osteoarthritis have no knee pain. The decision rests on what you have stopped doing, whether the knee wakes you at night, and what has already been tried.
Will waiting make the operation harder?
Not the operation itself, within reason. What waiting changes is you. People who wait until they are housebound arrive deconditioned with wasted quadriceps and a stiff joint, and poorer function before surgery predicts poorer function after it.
Is there any urgency with knee arthritis?
Almost never. Knee arthritis is not dangerous, so the timing is genuinely yours to choose around work, family and the rest of your life.
What if I am told I am too young?
That is a judgement about lifetime revision risk rather than about your age as such. It is set out in am I too young for a knee replacement, along with what is worth trying first and which alternatives exist.
This page provides general information about a medical condition and a surgical procedure. It is not individual medical advice and does not replace consultation with a qualified practitioner. Outcomes vary between individuals and all surgery carries risk. A referral is needed for a consultation with Professor Daevyd Rodda; without one, you can start with the practice nurse practitioner, who can provide it.