Various types of knee replacement surgeries are a popular choice for people with intractable knee pain. As the technology improves, it’s also becoming available to younger patients. It is a huge industry, delivering hundreds of thousands of knee replacements annually in the US, and millions globally.
That’s a lot of bionic knees.
This short article raises doubts and concerns about the efficacy of knee replacement.
Only you and your surgeon can decide if it’s a good idea for you, but I hope some of these points will contribute to that conversation.
Just one study of the right type
There’s a great deal of research on this topic, but almost none of the kind that we actually need to determine the efficacy of any treatment. Just one, in fact. And it only gets us halfway there: one prominent study that has directly compared surgery to doing nothing.1
The New England Journal of Medicine reported in 2015 that surgery was found to relieve pain better, but also had a lot more complications.
That’s roughly a tie between the pros and the cons. Which is not a particularly encouraging outcome. It isn’t definitive either (and no single study ever can be).
High-quality evidence to support the effectiveness of the procedure, as compared with nonsurgical interventions, is lacking.
~ Skou et al, 2015, New England Journal of Medicine
Still no placebo-controlled trials… for one of the most profitable procedures in the history of medicine
What if the pain relief reported by Skou et al wasn’t actually caused by the surgery? What if a fake surgery had the same effect? Just putting someone under, cutting them open, and then closing them up again?
There’s a strong possibility that the pain relief may have been entirely or substantially driven by placebo. Surgery can be an extremely powerful generator of placebo effects, because of the strong hopes it generates.
But there are no placebo-controlled trials of knee replacement at all yet, despite the existence of many analogous studies for other orthopedic surgeries… most of which have demonstrated that pain relief still occurs with sham surgery. Such research is quite a recent development.
The active ingredient of surgery is often faith, not what the surgeon actually does. This has been shown clearly enough now that it would be foolish to assume that knee replacement is any different.2345 It might be different. Some procedures, for some patients, clearly have value. But it’s not a safe assumption, not by a long shot.
So why does everyone seem to act like knee replacement is evidence-based?
If you browse scientific paper conclusions casually, it would be easy to think that everything in Knee Replacement Land is pretty great. Start reading more carefully, however, and the caveats are everywhere.
Even patient satisfication scores — which are grossly inadequate and misleading evidence even when done right6 — have been measured with a valid method in only 13% of more than 200 studies.7 A bad outcome measure measured badly… but that is the kind of data that’s being used to convince people that knee replacements are good medicine for arthritis.
It’s all much ado about nothing without properly controlled studies (fair tests between comparison to non-intervention and placebo groups). Without those, we cannot even know if knee replacement is efficacious. This is unambiguously true, science 101.
Orthopedic surgery as a profession has much to be ashamed of: decades of much lower standards for evidence-based care than have been considered normal in virtually every other part of health care, even long before evidence-based medicine got more rigorous in the 90s.8 They have been working in a little bubble of authority-based medicine, where RCTs have been considered unnecessary or impossible, both of which are absurd.9 It will probably take a new generation of surgeons to move beyond this.
It is difficult to get a man to understand something when his job depends on not understanding it.
~ Upton Sinclair
Is pain after surgery a complication or a normal side effect?
About 20% of patients who undergo knee replacement suffer from moderate to severe pain six months after the operation, and 16% were still in trouble at 12 months.10 The patients who suffered this unpleasant outcome were more anxious by nature (“trait” anxiety as opposed to “state”), had more pain before surgery than average, and expected more pain after.
A lot of patients with pain after surgery are told that it’s “normal.” This can be completely correct and fine in the short term, or incompetent evasion later on.
Increased persistent pain is always considered a complication. However it’s a bit complicated by the fact that some degree of post-surgical pain is normal — but exactly how much and for how long? At what point do you say that post-surgical pain is a complication rather than an expected side effect? There’s such a wide gray zone in there that, in general, pain levels in the first few months are rarely measured (or considered definitive). Instead, you measure pain levels many months or years after surgery. Increased pain at 3 months? Ambiguous. At 6 months? Starting to look like an adverse effect, but still ambiguous. A year? Definitely a complication.
Does knee replacement work? No one really knows, period — there simply isn’t enough of the right kind of evidence. It is effectively an experimental treatment.
Meanwhile, there is now substantial evidence that several similar surgeries cannot help people more than a sham.
If your surgeon reacts defensively to these concerns, seek a second opinion.
About Paul Ingraham
I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.
- PS Knee Surgery Sure is Useless! — Evidence that arthroscopic knee surgery for osteoarthritis is about as useful as a Nerf hammer
- PS Should You Get A Lube Job for Your Arthritic Knee? — Reviewing the science of injecting artificial synovial fluid, especially for patellofemoral pain
- PS MRI and X-Ray Often Worse than Useless for Back Pain — Medical guidelines “strongly” discourage the use of MRI and X-ray in diagnosing low back pain, because they produce so many false alarms
- PS Placebo Power Hype — The placebo effect is fascinating, but its “power” isn’t all it’s cracked up to be
- PS Does Cartilage Regeneration Work? — A review of knee cartilage “patching” with autologous chondrocyte implantation (ACI).
- Surgery: The ultimate placebo (book), by Ian Harris (book review).
What’s new in this article?
2019 — New section: “Is pain after surgery a complication or a normal side effect?”
2019 — Publication.
- Skou ST, Roos EM, Laursen MB, et al. A Randomized, Controlled Trial of Total Knee Replacement. N Engl J Med. 2015 Oct;373(17):1597–606. PubMed #26488691. ❐ BACK TO TEXT
- Louw A, Diener I, Fernández-de-Las-Peñas C, Puentedura EJ. Sham Surgery in Orthopedics: A Systematic Review of the Literature. Pain Med. 2016 Jul. PubMed #27402957. ❐ PainSci #53458. ❐
A review of a half dozen high quality tests of four popular orthopedic (“carpentry”) surgeries, all showing a lack of efficacy compared to placebos. As of 2016, this review is the best single academic citation to support the claim that “sham surgery has shown to be just as effective as actual surgery in reducing pain and disability.” It’s also an eyebrow-raiser that Louw et al could find only six good (controlled) trials of orthopedic surgeries, and all of them were bad news.BACK TO TEXT
- Thorlund JB, Juhl CB, Roos EM, Lohmander LS. Arthroscopic surgery for degenerative knee: systematic review and meta-analysis of benefits and harms. BMJ. 2015;350:h2747. PubMed #26080045. ❐ PainSci #53297. ❐
A review of nine studies presenting strong collective evidence that meniscectomy is a futile surgery for most patients, and with significant risk of harms to boot. For a good plain language overview of this topic, see Kolata.BACK TO TEXT
- Siemieniuk RA, Harris IA, Agoritsas T, et al. Arthroscopic surgery for degenerative knee arthritis and meniscal tears: a clinical practice guideline. BMJ. 2017 May;357:j1982. PubMed #28490431. ❐ PainSci #52778. ❐
These guidelines “make a strong recommendation against the use of arthroscopy in nearly all patients with degenerative knee disease … ” regardless of “imaging evidence of osteoarthritis, mechanical symptoms, or sudden symptom onset.” The authors believe this is the last word on the subject: “further research is unlikely to alter this recommendation.”BACK TO TEXT
- Blogs.BMJ.com [Internet]. Jevne J. The sexy scalpel: unnecessary shoulder surgery on the rise; 2015 Jan 27 [cited 19 Feb 20].
An excellent short opinion piece by Jørgen Jevne in the British Medical Journal about unnecessary shoulder surgeries, with broad applicability to other orthopedic surgeries.BACK TO TEXT
- Satisfaction measures are basically formalized anecdotal evidence, a popularity contest for treatments. It is practically the opposite of rigorous evidence. Human beings are routinely “satisfied” with treatments for a thousand reasons other than actual treatment efficacy, and have proven this again and again throughout medical history with astonishing examples of enthusiastically endorsing treatments that were actually hurting them, even killing them. See Popular but Weird & Dangerous Cures. BACK TO TEXT
- Kahlenberg CA, Nwachukwu BU, McLawhorn AS, et al. Patient Satisfaction After Total Knee Replacement: A Systematic Review. HSS J. 2018 Jul;14(2):192–201. PubMed #29983663. ❐ PainSci #52400. ❐ BACK TO TEXT
- Harris I. Surgery: The ultimate placebo. NewSouth Publishing; 2016. This excellent book by an orthopedic surgeon explores this shameful history in considerable detail. It’s fascinating and mostly easy enough reading even for patients. BACK TO TEXT
- Wartolowska K, Judge A, Hopewell S, et al. Use of placebo controls in the evaluation of surgery: systematic review. BMJ. 2014 May 21;348:g3253. PubMed #24850821. ❐ PainSci #53841. ❐ From the abstract: “Placebo controlled trial is a powerful, feasible way of showing the efficacy of surgical procedures. The risks of adverse effects associated with the placebo are small. In half of the studies, the results provide evidence against continued use of the investigated surgical procedures. Without well designed placebo controlled trials of surgery, ineffective treatment may continue unchallenged.” BACK TO TEXT
- Rice DA, Kluger MT, McNair PJ, et al. Persistent postoperative pain after total knee arthroplasty: a prospective cohort study of potential risk factors. Br J Anaesth. 2018 Oct;121(4):804–812. PubMed #30236242. ❐ BACK TO TEXT