Low-level Laser Treatment does not Improve Healing after TPLO Surgery in Dogs

I have been covering the subject of low-level, or “cold” laser treatment for many years. While there is some plausibility to the idea that laser light might have beneficial effects on tissue, very little convincing evidence of actual benefits in real patients. This is not surprising since the majority of good ideas that look promising on paper or in the lab fail to ever turn into safe and effective clinical treatments. Real life is more complicated than the research lab.

There have been very few clinical trials in dogs and cats, and most have had significant methodological limitations, so we can’t have much confidence in their findings. These findings, such as they are, have been mixed, with little consistent or compelling evidence of real-world benefits.

While this doesn’t mean lasers can’t be useful, it does mean that claims made for them by proponents, and the widespread use for many problems in dogs and cats, are based primarily on theory and anecdote, not on reliable research evidence. For something that is promoted as a dramatic breakthrough and is heavily marketed and widely used, it is surprising that it has been so difficult to actually demonstrate the supposedly amazing benefit in controlled research.

Another study has recently been published which follows up on the laboratory research suggesting laser might improve healing of bone and soft-tissue wounds. This is a well-conducted study with a reasonable number of patients, good control for bias and error (randomization, blinding, placebo controls, etc.), and reasonably reliable outcome measures. To steal my own thunder, it doesn’t look very good for laser therapy.

Renwick SM. Renwick AI. Brodbelt DC. et al. Influence of class IV laser therapy on the outcomes of tibial plateau leveling osteotomy in dogs. Veterinary Surgery. 2018: epub before print.

About a hundred dogs undergoing a TPLO (a common orthopedic surgery for cruciate ligament disease) were randomly assigned to receive laser treatments or placebo laser after the procedure. Though it’s not entirely clear if the people conducting the actual treatment were blinded to whether they were giving actual laser or placebo, everyone else (owners, surgeons, staff reading x-rays, etc.) appears to have been. The study used a couple of questionnaires to evaluate owners’ perceptions of comfort, function, and wound healing and had a surgical specialist evaluate the healing of the cut in the bone made as part of the procedure. Overall, none of these outcome measures showed any difference between real and fake laser treatment.

A subset of one questionnaire, looking at gait, did show a statistically significant difference between the treatments. This is not surprising since it is common for at least one outcome measures compared to show a statistical difference between treatments when many things are measured and compared. However, without a consistent pattern of such difference across outcomes, and with the difference in this particular measure being so small it is doubtful that it would be meaningful to the patients in terms of their comfort or function, the study provides pretty strong evidence against any value of laser therapy in these patients.

The authors, not surprisingly, emphasize the one small difference seen and suggest this might provide at least “mild clinical justification” for using lasers in patients undergoing TPLO. Personally, I think it is more reasonable to view the difference as a statistical fluke and to emphasize the failure to find any benefit in all the other measures evaluated, as well as the failure to show strong results in other clinical trials. Of course, there are many different techniques for using laser therapy, and proponents can always claim any single negative study is only negative because the technique used wasn’t quite right. This is the kind of “Yes, but….” Argument that supports the use of a lot of therapies even when clinical trial results consistently fail to find benefits. It is a reasonable argument up to a point, but eventually the failure to find positive effects does begin to suggest that there are none to find.

Absence of evidence can be evidence of absence once we’ve tried hard enough and long enough to find support for a scientific hypothesis. I don’t think we have reached that point yet with cold laser, and I do think more research is justified. However, it would be worthwhile for veterinarians and animal owners to be mindful that all the time and money being spent on laser treatment has so far not been proven worth it by good research, and in fact the balance of the evidence is not that encouraging.


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22 Responses to Low-level Laser Treatment does not Improve Healing after TPLO Surgery in Dogs

  1. This post was interesting and really timely for me. I happened to be reading about low level laser therapy for dogs with pyoderma and came across some clinical trails (past and present) that implied a good level of success.

    I’m glad I came upon your thoughts because it reminds me to think more critically.

  2. Jen Ehlers says:

    Agreed. We just had our 3 year old lab at a vet orthopedic specialist due to a “cyst” on a toe joint. Turns out it’s swelling due to a possible sprain….(poor guy hasn’t exhibited any signs of pain, so we feel especially bad for him!). She is suggesting splinting, with possible laser use to speed healing. Looks like we’ll splint without the laser–I don’t need the extra cost and time if there isn’t evidence to support it. He’s also been given gabapentin (which I’m not sold on) and carprofen (which does seem reasonable to hopefully reduce swelling).
    Sigh. It’s tough to find really good science-based care sometimes. Plus, I think we all want our pets to feel better, so it’s easy to get sucked into approaches that don’t work.

  3. H Case says:

    My dog had 2 laser sessions before a TPLO procedure, it reduced the swelling and made the surgery much simpler to perform. He has had several laser sessions post surgery and the improvement can be seen after each treatment. His recovery has been exceptionally fast and as he’s an old dog, I don’t think this could be explained as just co-incidence. I would recommend laser to anyone pre and post TPLO surgery. It may well be good for other conditions but I only have experience of TPLO surgery. After all it’s been trialled and used on humans in the UK’s National Health Service since the 1980’s with great success, so why shouldnt it be as successful on animals.

  4. skeptvet says:

    How do you know the surgery was “simpler to perform?” What does this mean?

    How do you know the laser is why he recovered quickly? Could it not have been any one of the other dozens of variables that differ between patients and procedures?

    Unfortunately, there are many explanations for the differences we see between patients and between specific surgeries besides the one that we may tend to think about or focus on, which is one of the many reasons such anecdotes can’t be trusted:

    Why Anecdotes Can’t Be Trusted

  5. Bill says:

    Have your read the following study. If so your thoughts?


  6. skeptvet says:

    Looks interesting. Unfortunately, I can’t find a full-text copy, so I can’t evaluate it fully. Can Vet J usually makes articles open access after a blackout period, so hopefully eventually I’ll be able to get the study report and assess it. Thanks for the link!

  7. mark carlson says:

    Brennen, once again kudos for your efforts. Have you reviewed the Can Vet J study yet? Just had the salesman for Companion lasers in today and he mentioned there is a new study being published on laser therapy of degenerative myelopathy and another treating cutaneous mast cell tumors (after gold nanoparticle injection). According to him therapeutic lasers are the rage in the human field. Is it common for MDs to embrace questionable technology and insurance to pay for it without some decent evidence? How is it they are using this without reliable oversight? Are the universities that are using this sold on it or just testing the waters?
    Thanks again and keep up the good work.

  8. skeptvet says:

    I haven’t seen the Can Vet J study. Can you post a link?

    Skepticism and critical thinking are pretty uncommon, in medicine and generally. If someone hears a positive anecdote or sees a small pilot trial or pre-clinical lab study that looks good, they often “try out” the therapy, and then confirmation bias makes it look like it works. MDs are a bit more constrained by evidence and things like regulations/insurance reimbursement than we are, but the type of problems are the same.

  9. Angie says:

    Dear Skeptvet,

    I have always said that I wish a vet could measure or actually see pain in pets. Too bad I didn’t know about this before my pups passed away. What are your thoughts?


  10. skeptvet says:

    The claims the company makes go WAY beyond any actual scientific evidence. There are a couple of studies looking at digital thermal imaging and pain or lameness, but they are small and have significant limitations. The technology has been around for decades and has never really been found useful enough to become widely used, which doesn’t suggest it’s all that great. It would be interesting to see some robust studies, but for now, there is a lot less evidence supporting this than there is for validated pain scales, such as the CSU or Glasgow scales. I don’t think you missed a big opportunity to care for your pets more effectively but not using this.

  11. Kelly Butz says:

    I’m getting ready to send my dog for TTA Surgery for a partially torn ACL. I’ve had feedback from people who say to try acupuncture and laser therapy instead of surgery. Thoughts?

  12. skeptvet says:

    There is no reliable evidence that either of these treatments provides significant benefits for CCL disease in dogs. The data are limited, but what exists is not encouraging. If medical therapy (pain control, weight control, possibly physical therapy) are not sufficient, surgery seems more likely than either of these methods to help your dog be comfortable and functional.

    Good luck!

  13. Jackie says:

    Here’s the full text link, please update either way. I really would love to read your thoughts on this.
    Thank you!


  14. skeptvet says:

    Thanks for the link. It is an encouraging study if the results are repeatable. Methodology seems generally sound, though as always there are a few weak points. As the authors note, small study. Also, there was a significant difference in the NSAID use between the groups.Half of the laser group were taking meloxicam, while only 1/10 of the control group used this medication. If for some reason this was a more effective treatment than the other NSAIDs, that alone would create the impression of a benefit.

    Also, the way effect was measured was a bit unusual- success at reducing existing NSAID dose 50%. If the dogs were on an appropriate dose to begin with, there is no reason to reduce it unless there are adverse effects. And it is likely that a lower dose would be less effective. If laser reduces pain, why would it not be an adjunct to NSAID rather than a “replacement” for half the NSAID dose? This isn’t how I expect it is used in the real world.

    The authors list a number of other limitations to the study. All studies are imperfect, of course, so nothing unusual about this one in that respect. What would be stronger evidence would be other research groups repeating these findings consistently. Let me know if you see such evidence. Thanks again!

  15. Jill says:

    There is a huge amount of evidence regarding laser from human studies so its not strictly correct to say that evidence of effect doesn’t exist.

  16. skeptvet says:

    I’m pretty sure if your read carefully, I didn’t say “evidence of effect doesn’t exist” for humans. However, the level of evidence for recommended uses in veterinary patients is minimal and poor quality.

  17. Ewen Bennett says:

    The Skepdoc looking at human studies also concluded that

    “The use of therapeutic lasers by veterinarians and medical doctors is not warranted by the existing scientific evidence. As the Mayo Clinic says, “the question of whether these treatments offer hope, or are merely hype and hokum, is unanswered.”[x]”



  18. art malernee dvm says:

    came across this cruciate twitter this morning.


    When i did cruciate surgery i did not include in the informed consent that cruciate surgery does not repair the cruciate ligament. Someone should do a study to see what clients whose dogs and people who have had cruciate surgery themselves know about the cruciate repair surgery they paid for. I would guess that tplo clients are most likely to know the cruciate ligament surgery does not repair the ligament. A osu football player made a touchdown Saturday after having a record four cruciate surgeries. Would be nice to know the surgery techniques used. Was it just a clean up surgery that placebo fake incision surgery has not been shown to help over medical treatment long term but still done. From looking at this twitter picture you get the idea that the ligament will heal on its own without surgery. People know bones heal together when broke. People who pay for cruciate surgery need to know that is not going to happen to cruciate ligaments.

  19. Jill says:

    Thats because the studies are poorly conducted snd underpowered. Evidence from thousands of human studies proves the effect at tissue level. I think you know that.

  20. skeptvet says:

    “Effect at the tissue level” is not the same as clinical efficacy, which is why we run clinical trials for specific conditions we wish to treat. Lots of therapies look great in preclinical research, or in one species, and fail in real-life patients or in another species. If you read my articles on LLT closely, you will see that I reference both the promising positive evidence from lab studies and non-veterinary species, but that is only part of the story, and failure to prove efficacy in veterinary species and conditions can’t just be waved off as “underpowered studies.”

  21. Arthur Malernee dvm says:

    Medicare/ Medicaid and pet insurance is still paying for these unproven knee treatments even when we know they don’t work.

    From nyt. My favorite newspaper medical reporter A Knee Surgery for Arthritis Is Called Sham


    popular operation for arthritis of the knee worked no better than a sham procedure in which patients were sedated while surgeons pretended to operate, researchers are reporting today.

    The operation — arthroscopic surgery for the pain and stiffness caused by osteoarthritis — is done on at least 225,000 middle-age and older Americans each year at a cost of more than a billion dollars to Medicare, the Department of Veterans Affairs and private insurers.

    It involves making three small incisions in the knee; inserting an arthroscope, a thin instrument that allows surgeons to see the joint; and then flushing debris from the knee or shaving rough areas of cartilage from the joint and then flushing it.

    In the study, to be published today in The New England Journal of Medicine, investigators at the Houston Veterans Affairs Medical Center and Baylor College of Medicine report that while patients often said they felt better after the surgery, their improvement was just wishful thinking. Tests of knee functions revealed that the operation had not helped, and those who got the placebo surgery reported feeling just as good as those who had had the real operation.

    “Here we are doing all this surgery on people and it’s all a sham,” said Dr. Baruch Brody, an ethicist at Baylor who helped design the study.

    The study dealt only with arthroscopic surgery for osteoarthritis, not with other common knee operations.

    After learning of the results, Anthony J. Principi, the secretary of veterans affairs, said yesterday that the study would “change the practice of orthopedic medicine in the United States.”

    But Veterans Affairs Departmentofficials stopped short of saying they would no longer pay for the surgery. Medicare and private insurers typically review such studies before deciding whether to change their reimbursement practices.

    The 180 participants in the study were randomly assigned to have the operation or to have placebo surgery in which surgeons simply made cuts in their knees so the patients would not know if they had the surgery.

    After they recovered from the procedures, most patients said their knee pain had improved, and they continued to say they were better for the two years that the researchers followed their progress. But Dr. Nelda P. Wray, who is chief of the section of health services research at Baylor, said, “On the objective scale, no one was better at any time point.”

    Some orthopedists interviewed about the study said they had wondered for some time about the operation’s effectiveness. Dr. Kenneth Fine, an orthopedic surgeon at the George Washington University School of Medicine, said the procedure had long seemed to do nothing for patients’ underlying arthritis.

    “There are pretty good success rates in terms of patient satisfaction,” Dr. Fine said, “but I have always been skeptical.”

    Dr. William J. Tipton Jr., executive vice president and chief executive of the American Academy of Orthopedic Surgeons, also said he had questioned the operation.

    “I’m both a patient and a physician,” Dr. Tipton said, explaining that he has osteoarthritis. “My knee is buckling now, but I’m not going to have arthroscopy done. I recognize that it’s not going to help.”

    Still, he said he would like to see the study repeated before doctors decided whether to do the operation.

    “Gradually,” Dr. Tipton speculated, “physicians would say to their patients: `I know you’ve seen a lot about arthroscopy, but you know what? It doesn’t work very well for osteoarthritis of the knee.’ ”

    But a past president of the orthopedic surgeons’ academy, Dr. Douglas Jackson of Long Beach, Calif., said that the study’s population, mostly men in a veterans’ hospital, was not typical of what he had seen in his private practice, but that he would tell his patients about their experience.

    The research began when an orthopedic surgeon at the Houston veterans’ hospital, Dr. J. Bruce Moseley, who is now the team physician for Houston’s two professional basketball teams, approached Dr. Wray suggesting a study that would compare washing the knee joint with washing and scraping in patients with arthritis.

    Dr. Wray had a bolder idea.

    “She said, `How do you know that what you are seeing is not a placebo effect?’ ” Dr. Moseley recalled. “My response was, `This is surgery.’ She said, `I hate to tell you this, but surgery may have the biggest placebo effect of all.’ ”

    Placebo studies of surgery are almost never done. Many doctors consider them unethical because patients could undergo risks with no benefits. Working with Dr. Brody, the ethicist, the group tried to make the placebo treatment no more dangerous than daily life. Still, of 324 consecutive patients who were asked to participate, 144 declined.

    For those who agreed, the day of surgery meant being wheeled into an operating room while neither they nor any of the medical staff knew what their treatment would be. When they were on the operating table, Dr. Moseley, who did all the operations, opened a sealed envelope telling him whether the patient was to have the surgery or not.

    Those in the placebo group received a drug that put them to sleep. Unlike those getting the real operation, they did not have general anesthesia.

    Dr. Moseley made small cuts in their knees to simulate an operation. He bent and straightened the knee and asked for surgical instruments, just in case the patient was partly conscious. An assistant sloshed water in a bucket to make the sound of a knee being flushed clean.

    The paper in The New England Journal is accompanied by two editorials. One, by Sam Horng and Dr. Franklin G. Miller of the National Institutes of Health, asks whether placebo surgery is unethical. The controversy, they wrote, comes because doctors assume that patients in clinical research should not be put at risk if they cannot benefit, and placebo surgery involves risk.

    But, they say, clinical research is different from medical therapy; its aim is not to help those in the study but to help future patients.

    To be ethical, they say, a study with placebo surgery must meet three criteria: it must not place patients at undue risk; the benefits of learning whether the surgery works must be worth any potential risk to the patients; and the patients must give informed consent.

    In the current case, they wrote, all those objectives were met and the study “exemplifies the ethically justified use of placebo surgery.”

    In the second editorial, Dr. David T. Felson of Boston University and Dr. Joseph Buckwalter of the University of Iowa note that if there were large beneficial effects from the surgery, the study should have found them.

    “Although the study may not have been large enough to permit the detection of any small effects,” they wrote, “the data presented do not suggest that there were any.,”

    In a telephone interview this week, Dr. Felson, a professor of medicine and a rheumatologist by training, praised the research but said it remained to be seen whether doctors and patients would abandon the procedure.

    “There’s a pretty good-sized industry out there that is performing this surgery,” Dr. Felton said. “It constitutes a good part of the livelihood of some orthopedic surgeons. That is a reality.”

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