Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up
BMJ 2016; 354 doi: https://doi.org/10.1136/bmj.i3740 (Published 20 July 2016) Cite this as: BMJ 2016;354:i3740
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Dear authors,
Thank you for this outstanding study, titled “Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up (1). Orthopaedic surgeons should encourage middle-aged patients with degenerative meniscal tear to undergo exercise therapy before they eventually proceed to surgery.
However, I would like to discuss a few important issues that might weaken the conclusions of this paper.
All 16 variables in the baseline scores are somewhat better in the meniscectomy group, indicating that there must be a selection bias. The result is that, although it is a randomised trial, the two study groups are not equal.
The power of patient reported outcome measures (PROMs) to distinguish between treatments have been questioned (2-4). One reason for this could be the presence of ceiling effects. Ceiling effects up to 36% have been reported for the KOOS (2, 4, 5), and the problem is that high ceiling effects reduce the responsiveness of an assessment tool in the high-end of the scale. In other words, if the PROM exhibits a high ceiling effect, it will not be able to detect differences between good results and very good results. In the present study, the baseline scores are higher in the meniscectomy group, therefore this group is even more sensitive for ceiling effects than the exercise group. In the discussion chapter you state; “Their better baseline status may have provided participants in the meniscectomy group with an advantage, and, if anything, better results at follow-ups would be expected.” This may be true only if no ceiling effect exists. If there is a ceiling effect, the opposite may result because it is less space for improvement underneath the ceiling for the meniscectomy group. However, ceiling effects differ between populations and are highly dependent on context, so to clarify this potential problem, could you please publish the exact ceiling effect at 2 years follow up for all subscores in KOOS?
The placebo effect in surgery is well known. However, the exercise group was offered training at the Norwegian Sports Medicine Clinic. The placebo effect of this context is unknown, but should probably not be underestimated.
Some endpoints in your study are based on muscle strength and performance tests. These tests have interesting properties and may be less prone to ceiling effects, but they are only surrogate endpoints for the true clinical result. A valid surrogate endpoint must be on the causal pathway between intervention and the true clinical outcome (6). The problem in the present study is that the surrogate endpoint is obviously in the pathway between exercise therapy and real clinical outcome, but probably not in the pathway between meniscectomy and real clinical outcome. Therefore, as long as the meniscectomy group was given written and oral instructions for simple home exercises, and the exercise group were offered supervised progressive neuromuscular and strength exercises over 12 weeks at a highly specialized centre, it is not surprising that the last group performs best in tests. It should be evident that if one study group of patients get specific strength exercises and the other not, specific strength testing is not a valid endpoint.
Consequently, in my opinion, the performance and strength tests are not valid outcome measures and it is hard to understand how this mistake has passed through the publication process of this otherwise very inspiring paper.
Eirik Aunan, MD
eirik.aunan@sykehuset-innlandet.no
Department of Surgery, Innlandet Hospital Trust
Lillehammer, Norway
References
1. Kise NJ, Risberg MA, Stensrud S, Ranstam J, Engebretsen L, Roos EM. Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up. BMJ. 2016;354:i3740.
2. van de Graaf VA, Wolterbeek N, Scholtes VA, Mutsaerts EL, Poolman RW. Reliability and Validity of the IKDC, KOOS, and WOMAC for Patients With Meniscal Injuries. Am J Sports Med. 2014;42(6):1408-16.
3. Hossain FS, Konan S, Patel S, Rodriguez-Merchan EC, Haddad FS. The assessment of outcome after total knee arthroplasty: are we there yet? Bone Joint J. 2015;97-B(1):3-9.
4. Aunan E, Naess G, Clarke-Jenssen J, Sandvik L, Kibsgard TJ. Patellar resurfacing in total knee arthroplasty: functional outcome differs with different outcome scores: A randomized, double-blind study of 129 knees with 3 years of follow-up. Acta Orthop. 2016;87(2):158-64.
5. Roos EM, Toksvig-Larsen S. Knee injury and Osteoarthritis Outcome Score (KOOS) - validation and comparison to the WOMAC in total knee replacement. Health QualLife Outcomes. 2003;1(1):17.
6. Fleming TR, DeMets DL. Surrogate end points in clinical trials: are we being misled? Ann Intern Med. 1996;125(7):605-13.
Competing interests: No competing interests
This is one of numerous other randomized trials which confirm that arthroscopic sugery does not supply any benefit treating knee pain resulting from degenerative meniscal tears and other cartilage demage other than severe osteoarthritis.
The task physicians are facing now is to support patients seeking to take personal responsibility by self administered exercise, discussing what will reach a better outcome and at least better self sufficiency than technical solutions. This is the key role physicians have to resume: they have to create a bearing and sustainable patient-doctor-relationship to get the patient acting. Physicians have to learn to be reluctant.
Competing interests: No competing interests
We thank Dr. Chitnavis for his interest in our recent publication.(1)
Dr. Chitnavis wonders if the reason why surgery was not superior in our study was that patients were not selected appropriately and suggest that “Those with focal joint line pain and tenderness associated with rotational irritability lacking significant chondral wear are good candidates for surgery”. We respectfully disagree, since our results suggest otherwise. Patients in both treatment groups suffered from these signs and symptoms to a similar degree and improved to a similar degree after having three months of twice weekly exercise therapy or arthroscopic partial meniscectomy. Unfortunately, we did not ask for joint line pain but we did ask for ‘pain when twisting or pivoting on knee’ and did assess chondral wear. ‘At least moderate pain when twisting on knee’ was similarly common in both treatment groups at baseline (61.4% vs. 62.9%) as were radiographic status and MRI-verified structural change.(1) Improvements were similar among all self-reported outcomes except ‘symptoms’ and in muscle strength were the exercise therapy group improved significantly more.(1)
Dr. Chitnavis also wonders what to do when the patient has failed ‘reasonable non-operative intervention’. We suggest raising the bar for what a ‘reasonable non-operative intervention’ program is. Exercise means very different things to different patients and medical practitioners. While for example soccer and running fits under the definition of exercise (“physical activity which is usually regular and done with the intention of improving or maintaining physical fitness or health”) it is inappropriate as treatment for knee problems. In this study we used ‘exercise therapy’ defined as “A regimen or plan of physical activities designed and prescribed for specific therapeutic goals. Its purpose is to restore normal musculoskeletal function or to reduce pain caused by disease or injuries”. We used specifically designed neuromuscular exercises and strength training exercises administered twice weekly for 12 weeks, individualized to the patient and supervised by a physical therapist. The number of repetitions and resistance of each strength training exercise were increased when possible to ensure progressive overload. The neuromuscular exercises were progressed by changing the support surface or including more challenging exercises.(2) It is reasonable to expect that exercise therapy is prescribed and supervised by professionals with the same level of expertise as surgical treatment.
Finally, we do agree with Dr. Chitnavis that randomized controlled trials are not without their own limitations and challenges. It is true that 17% of patients in the exercise therapy group opted for surgery. However doing so was not associated with any additional benefit.(1, 3)
References:
1. Kise NJ, Risberg MA, Stensrud S, Ranstam J, Engebretsen L, Roos EM. Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up. BMJ (Clinical research ed). 2016;354:i3740.
2. Stensrud S, Roos EM, Risberg MA. A 12-week exercise therapy program in middle-aged patients with degenerative meniscus tears: a case series with 1-year follow-up. The Journal of orthopaedic and sports physical therapy. 2012;42(11):919-31.
3. Kise NJ RM, Stensrud S, Ranstam J, Engebretsen L, Roos EM. 2016 [Available from: http://www.bmj.com/content/bmj/suppl/2016/07/19/bmj.i3740.DC1/kisn030744....
Competing interests: No competing interests
We thank Dr. Twyman for his interest in our recent publication.(1)
We agree with Dr. Twyman that horizontal cleavage tears, also called degenerative meniscal tears, are unlikely to benefit more from surgery than exercise therapy. This is what we showed in our study, a finding in line with the findings from the other randomized studies(2-7) where knee arthroscopy was compared or added to other treatments performed in different age groups, in patients of different physical activity levels, in patients from different countries and cultures, and in those with or without radiographic signs of osteoarthritis.(8)
We studied middle-aged patients with prolonged knee pain. The presence of a degenerative meniscal tear was confirmed by MRI. Patients over 60 and those with osteoarthritis were not included. Likewise, and notably, patients younger than 35, those presenting with a bucket handle tear on MRI, and patients whose knee problems originated from a significant trauma in sports were not included in our study.(1) The mean age of participants in our study (∼ 49 years) is representative of the current mean ages of patients having knee arthroscopy for a degenerative meniscal tear in Sweden (47 years) and Finland (52 years).(9) In Denmark, the overall mean age for patients having meniscal surgery is 47.(10) The most common patient having meniscal surgery is middle-aged and patients younger than 35 years old are a minority and nowadays constitute only 25% of those having meniscal surgery compared to 35% a decade ago.(10) Our study included younger, slimmer and more physically active patients compared to most previous studies, but did not include the young with traumatic tears. We welcome rigorous studies studying the subgroup of young patients with a traumatic tear to expand our understanding of this complex area.
Dr. Twyman is concerned about selection bias in our study and is of the opinion that “It would not be unreasonable to conclude the 23% who declined to enter the exercise arm of this study, 52 of the 226 eligible, realising exercise would not resolve their mechanical symptoms self-selected themselves out and opted for an arthroscopy.” While it is true that more patients (n=52) declined trial participation because they were not willing to undergo exercise therapy than those refusing surgery (n=17), our results do not substantiate the belief that exercise therapy would not resolve mechanical problems. Quite on the contrary, mechanical symptoms like catching, grinding and clicking were relieved following 3 months of twice weekly exercise therapy and further improvement was seen during the two years. Actually, at the final follow-up at 2 years the improvement in the subscale score evaluating ‘symptoms’ was significantly greater in the exercise therapy group than in the arthroscopy group.(1)
Our study, as all rigorously performed randomized controlled trials, applied an intention-to-treat analysis where all patients randomized were included. Excluding the single patient with grade 3 osteoarthritis, or this patient combined with the two patients having osteotomy did not change the results.
Lastly, we would like to point out a misunderstanding. The sport and recreation score was not significantly better in those who had arthroscopic surgery. On the contrary, the only statistically significant self-reported treatment group difference at 2 years was for symptoms (swelling, grinding, clicking, catching, range of motion and stiffness) where the exercise therapy group reported a 5.3-point greater improvement on a 0-100 scale.(1)
References:
1. Kise NJ, Risberg MA, Stensrud S, Ranstam J, Engebretsen L, Roos EM. Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up. BMJ (Clinical research ed). 2016;354:i3740.
2. Gauffin H, Tagesson S, Meunier A, Magnusson H, Kvist J. Knee arthroscopic surgery is beneficial to middle-aged patients with meniscal symptoms: a prospective, randomised, single-blinded study. Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society. 2014;22(11):1808-16.
3. Herrlin S, Hallander M, Wange P, Weidenhielm L, Werner S. Arthroscopic or conservative treatment of degenerative medial meniscal tears: a prospective randomised trial. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. 2007;15(4):393-401.
4. Herrlin SV, Wange PO, Lapidus G, Hallander M, Werner S, Weidenhielm L. Is arthroscopic surgery beneficial in treating non-traumatic, degenerative medial meniscal tears? A five year follow-up. Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA. 2013;21(2):358-64.
5. Katz JN, Brophy RH, Chaisson CE, de Chaves L, Cole BJ, Dahm DL, et al. Surgery versus physical therapy for a meniscal tear and osteoarthritis. The New England journal of medicine. 2013;368(18):1675-84.
6. Sihvonen R, Paavola M, Malmivaara A, Itala A, Joukainen A, Nurmi H, et al. Arthroscopic partial meniscectomy versus sham surgery for a degenerative meniscal tear. The New England journal of medicine. 2013;369(26):2515-24.
7. Yim JH, Seon JK, Song EK, Choi JI, Kim MC, Lee KB, et al. A comparative study of meniscectomy and nonoperative treatment for degenerative horizontal tears of the medial meniscus. The American journal of sports medicine. 2013;41(7):1565-70.
8. Thorlund JB, Juhl CB, Roos EM, Lohmander LS. Arthroscopic surgery for degenerative knee: systematic review and meta-analysis of benefits and harms. BMJ (Clinical research ed). 2015;350:h2747.
9. Mattila VM, Sihvonen R, Paloneva J, Fellander-Tsai L. Changes in rates of arthroscopy due to degenerative knee disease and traumatic meniscal tears in Finland and Sweden. Acta orthopaedica. 2015:1-7.
10. Thorlund JB, Hare KB, Lohmander LS. Large increase in arthroscopic meniscus surgery in the middle-aged and older population in Denmark from 2000 to 2011. Acta orthopaedica. 2014;85(3):287-92.
Competing interests: No competing interests
We thank Dr. Joshi for his interest in our recent publication.(1)
We certainly agree with Dr. Joshi that the finding of a degenerative meniscal tear on MRI is no cause for treatment, surgical or non-surgical, and that the common use of MRI in middle-aged and elderly patients with chronic knee pain is costly and unwarranted. The increasing accessibility to MRI is indeed a likely contributor to the current high rate of arthroscopic knee surgery in the middle-aged and elderly population since once a tear is shown, it begs to be treated even in the absence of a proven cause of symptoms.
Asymptomatic MRI-verified meniscal tears are common in the population(2) and the poor correlation between symptoms and MRI findings is well established, also in orthopedic populations(3, 4). Rather it is pain, mechanical symptoms, impaired function and the resulting reduction in quality of life that drives the patient to seek treatment, and where the expectation of relief lies. Our study showed equal improvement between treatment groups in these aspects, except for ‘symptoms’ which were significantly more improved in the exercise therapy group.(1) Neither clinical assessment nor patient symptoms could differentiate a group improving more from surgery. We therefore disagree with Dr. Joshi’s statement that “A good clinical assessment correlated with detailed patient symptoms is a good enough for the surgeon to decide which patient needs an arthroscopy”.
Dr. Joshi also states that “…with exercise therapy alone the torn meniscus continues to cause obstructive symptoms…” and “Any pt between age group 35 to 60 would never want to continue doing sporting activities knowing the fact that a meniscal tear is sitting inside their knee”. We allow ourselves to point out that these statements are opinions only. Fact is that exercise therapy was associated with immediate and sustained relief in mechanical and other symptoms. In the exercise therapy group the percentage of participants who reported ‘at least moderate problems with their knee catching or hanging up’ decreased from 24% at baseline to 6% at 2 years. Similar improvements were seen for ‘at least moderate grinding, clicking and other noise’ (decreased from 59% to 29%) and ‘at least moderate pain when bending knee’ (decreased from 58% to 16%). In addition, ‘at least moderate problems with swelling and stiffness’ decreased (49% to 14% and 49% to 10%) after exercise therapy.
Participants in our study were younger, slimmer and more physically active compared to previous studies. They were also eager to return to physical activity. The HUNT activity index, measuring frequency, duration and intensity of their physical activities, improved with 1.4 points in the exercise group compared with 0.9 in the knee arthroscopy group.
Surgeons, GPs, physiotherapists and others who meet these patients in their medical practice can comfortably inform about these facts when engaging their patients in shared decision making about their treatment. As suggested by Dr. Finnikin in a rapid response(5) to the accompanying editorial(6) “shared decision-making should begin in the GP surgery and continue through the patient’s treatment. Given the research findings, it would be difficult to see why patients who are adequately supported in the decision making process would be choosing surgery over physiotherapy”.
References:
1. Kise NJ, Risberg MA, Stensrud S, Ranstam J, Engebretsen L, Roos EM. Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up. BMJ (Clinical research ed). 2016;354:i3740.
2. Englund M, Guermazi A, Gale D, Hunter DJ, Aliabadi P, Clancy M, et al. Incidental Meniscal Findings on Knee MRI in Middle-Aged and Elderly Persons. New England Journal of Medicine. 2008;359(11):1108-15.
3. Buck FM, Hoffmann A, Hofer B, Pfirrmann CW, Allgayer B. Chronic medial knee pain without history of prior trauma: correlation of pain at rest and during exercise using bone scintigraphy and MR imaging. Skeletal radiology. 2009;38(4):339-47.
4. Bhattacharyya T, Gale D, Dewire P, Totterman S, Gale ME, McLaughlin S, et al. The clinical importance of meniscal tears demonstrated by magnetic resonance imaging in osteoarthritis of the knee. The Journal of bone and joint surgery American volume. 2003;85-a(1):4-9.
5. Finnikin. 2016 [Available from: http://www.bmj.com/content/354/bmj.i3934/rapid-responses.
6. Jarvinen TL, Guyatt GH. Arthroscopic surgery for knee pain. BMJ (Clinical research ed). 2016;354:i3934.
Competing interests: No competing interests
Interesting study on Arthroscopic surgery for knee pain by Kise NJ et al (BMJ 23rd July 2016;354:i3740). They have concluded that exercise therapy is better for thigh muscle strength than surgery.
I would like to raise the following points on this article. The study performed MRI in every pt to diagnose meniscal tears. This seems a bit impractical in the current scenario with dwindling funding for hospitals, increasing demand by population on MRI where waiting times are already very high. A good clinical assessment correlated with details pt symptoms is a good enough for the surgeon to decide which pt needs an arthroscopy and MRI in the remainder when the surgeon is unsure about the diagnosis.
Secondly in degenerate meniscal tears physiotherapy may increase muscle strength but shall never resolve the mechanical symptoms like locking of knee, clicking, intermittent swelling and effusion besides on going pain. Arthroscopic surgery primarily aims at resolving mechanical symptoms due to flap tears by smoothening the motion and removing mechanical obstruction. With exercise alone the meniscal tear continues to remain or worsen over period of time.
In my opinion exercise regime shall always remain supplementary to arthroscopic surgery in select cases where surgery is indicated and to improve function and strength post operatively. It can never replace arthroscopy as primary modality of treatment. Lastly with exercise therapy alone the torn meniscus continues to cause obstructive symptoms exposing pts to increased tendency for further falls risking themselves for fractures in hip, ankle or wrist. Any pt between age group 35 to 60 would never want to continue doing sporting activities knowing the fact that a meniscal tear is sitting inside their knee.
Avinash Joshi
(Mch, FRCS, MS - Orth)
Orthopaedic Consultant
Jersey General Hospital
nashjoshi@hotmail.com
Competing interests: No competing interests
Kise et al (research 23 July) conclude that a prolonged intensive exercise programme is as effective as arthroscopy in treating degenerative meniscal tears in middle-aged patients without osteoarthritis. It is unusual when a surgical treatment is being assessed for so little information to be given in reporting its indications, any operative findings or the procedure itself.
Just as not every patient with chest pain and an abnormal angiogram requires cardiac by-pass surgery not every patient with knee pain and a MRI proven meniscal tear requires an arthroscopy. There is a wide spectrum of types of meniscal tears from horizontal cleavage tears, most of which are unlikely to benefit from surgery, to flap and bucket handle tears causing mechanical symptoms as they become trapped between the joint surfaces. There is no attempt to differentiate by symptoms between these in this study or indeed many other similar papers but an over-reliance on MRI. Even so 9% of patients had MRI grade 1 or 2 meniscal pathology that according to Crues et al’s (1987) original study quoted in this paper did not correlate with presence of a tear at arthroscopy.
There are concerns of selection bias. It would not be unreasonable to conclude the 23% who declined to enter the exercise arm of this study, 52 of the 226 eligible, realising exercise would not resolve their mechanical symptoms self-selected themselves out and opted for an arthroscopy.
There is no specific information on the temporal delay in starting treatment other than to suggest it was different in the 2 groups allowing symptoms to naturally settle in one group but not the other prior to the intervention which explains why 7% who had been randomised to the arthroscopic arm had too few symptoms on the day to undergo the procedure
Other concerns also arise about the 19% of the exercise group patients who had arthroscopic surgery at various time points during the study. A patient with grade 3 osteoarthritis that is specifically ineligible by the study criteria and 2 patients who had osteotomies, presumably for osteoarthritis, during the study period and included in the analysis
Only 34 (49%) of the selected patients completed the exercise arm as planned
The significance of the greater muscle strength at 12 months in the exercise group is questionable when the sport and recreational function was significantly better in those who had an arthroscopy
Far from, as the Commentary states, it being a ‘rigorous’ study it provides a simplistic view of a complex and controversial area in which, had important variables not been ignored very different conclusions may have been reached and the indications for this operation been better defined. A missed opportunity
It should be remembered by all those who care or research patients with knee pain that MRI should be used to confirm the clinical suspicion that an arthroscopy is required rather than using it as a screening tool
Competing interests: I am an Orthopaedic Surgeon specialising in Knee Surgery
'A highly questionable practice without supporting evidence of even moderate quality'
Experienced knee surgeons must be doing something right with arthroscopic meniscectomy.
We have happy patients who rarely have significant complications. They often return asking for their other knee to be managed for the same problem, years later.
Perhaps the problem lies with selecting patients appropriately?
Those with focal joint line pain and tenderness associated with rotational irritability lacking significant chondral wear are good candidates for surgery. Assuming, where possible, a trial of about 3 months of non-operative intervention has failed.
In my view, certain tear patterns are more troublesome than others. Unstable vertical tears in particular cause recurrent pain.
The cause for the pain is visible at arthroscopy as localised synovitis in the periphery of the tear. Lacking free blood flow within their cavities, synovial joints simply cannot remove torn fibrocartilage. All the joint can do is to extrude such material into the periphery of the joint, irritating the very sensitive synovium adjacent the tear.
When patients come to surgeons and have failed reasonable non-operative intervention what are we to do? And how long should we wait? Or are the authors advocating abandoning arthroscopic surgery altogether for knee pain of any cause?
Yes, there is a proportion which fails to improve and a very small number who get worse after surgery. I looked at 80 partial menisectomies I undertook in 2012 in those of 'middle-age' or older; by 2015, 9 (11%) had undergone knee arthroplasty or osteotomy. Is that 'questionable practice'? Perhaps I should have left them in pain or undertaken major surgery instead! Remember, many have already tried physiotherapy.
Randomised controlled trials are not without their own limitations.
In the published study nearly 20% of those in the non-operative group abandoned physiotherapy and chose surgery. And more than 20% did not comply with exercise....
Jai Chitnavis
Competing interests: Practising Consultant Orthopaedic Surgeon
I have anaesthetised patients having therapeutic arthroscopy for knee pain since 1979 and have followed the debate on the virtues of this treatment with increasing bemusement. I respectfully wish to state that, in my experience, there is a wide spectrum of understanding amongst surgeons performing knee arthroscopy of the causes and arthroscopic management of knee pain. The cause of pain is clearly not always due to intrinsic meniscal pathology. For example, the teaching and understanding of infrapatellar pathology and its management options is at best variable.
I work with 2 surgeons who regularly treat, with success, patients seeking a further opinion after less than satisfactory results from both conservative and arthroscopic management of their knee pain by other colleagues. The current level of debate is naïve; inappropriately managed problems will result in premature arthritis. I suggest there is no shortage of sham surgery already being performed as the patients in this study by Kise NJ et al have experienced. There again, this is just the view of an anaesthetist.
Competing interests: I have an active private anaesthetic practice with regular orthopaedic sessions. I have anaesthetised more than 300 patients for knee pain in the last 24 months.
Re: Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up
We thank Dr. Schiltenwolf for sharing his perspective on the increasingly important role of physicians in managing middle-aged patients with best practice treatments. We also thank Dr. Aunan for his thoughtful comments on study design and choice of outcomes in our trial comparing exercise therapy to arthroscopic partial meniscectomy.
Selection bias
Randomized allocation of patients de facto excludes selection bias. To account for baseline random imbalances, in our study in favor of the meniscectomy group, these were adjusted for in the change from baseline analyses.1
KOOS Ceiling effects
Despite a 5.3 point better mean baseline KOOS4 score in the meniscectomy group, the mean baseline score of 59.6, on a 0-100 worst to best scale, leaves room for improvement. A mean score of 50 corresponds to on average moderate problems, and will allow for the patient to improve to on average mild (score of 75) and no (score of 100) problems. On an individual patient level, there was no ceiling effect for KOOS4 at baseline since no patients exhibited the best possible KOOS4 score (100), confirming that all patients could report improvement on the primary outcome.
As recommended, the five individual KOOS subscales accompanied the KOOS4 as secondary outcomes to allow for clinical interpretation.2 The ADL subscale of the KOOS is well known for displaying ceiling effects in younger or more active people.3,4 This is due to poor content validity, few young and active persons find that knee injury has much impact on activities of daily living. We took this knowledge into account when designing the study and the ADL subscale is therefore not included in the primary outcome KOOS4. KOOS4 is an aggregate measure consisting of the mean subscale scores from the remaining four KOOS subscales Pain, Symptoms, Sport and Recreation Function and knee-related Quality of Life.
In response to Dr. Aunan’s request, we would like to disclose the ceiling effects for KOOS. However we suggest ceiling effects at baseline (instead of at follow-up) are more relevant since it is KOOS’ potential for improvement from baseline to follow-up that is of interest. We found very small ceiling effects for the KOOS subscales at baseline. At baseline 3.57% reported the best possible score (ceiling effect) for the subscale ADL. For the other subscales, the ceiling effects were: 0% (Pain), 3.57% (Symptoms), 1.43% (Sport/Rec), 0 % (QOL).
Dr. Aunan suggests ceiling effects may hamper a PROs ability to differentiate between good and very good results. We therefore calculated the difference in mean KOOS score between patients reporting to be “much better” and those reporting to be “better” on a five point global rating of change scale. While the difference between those reporting to be “much better” and “better” was only 3 points for the ADL subscale, it was 16.6 for the Sport and Recreation function subscale and 12 for the QOL subscale. For the primary outcome KOOS4 it was 9.4. We therefore believe KOOS was able to differentiate between good and very good results in this study.
As requested by Dr. Aunan we also calculated the percentage of patients who had baseline scores within the smallest detectable change for KOOS as presented by van de Graaf4 suggesting an improvement on an individual patient level could not be reliably detected. This comparison is however of less interest for the current study since results were reported as difference between group means and not between proportions of responders on an individual patient level. In addition, these data need to be interpreted with great caution for at least two reasons: first, psychometric properties for PROMs, including KOOS, established in one study are not necessarily transferrable to another study since they are known to vary with the characteristics of the cohort studied;3 second, the smallest detectable differences for KOOS reported by van de Graaf4 were established using a small sample of only 28 patients. For the 140 patients included in our study, the percentage of patients who at baseline had a KOOS score where an improvement in an individual patient could not reliably be detected spanned from 57.1% for the ADL subscale to 3.6% for the QOL subscale.
In summary, our additional analyses confirm our decision not to include the ADL subscale in the primary outcome KOOS4 and that improvement was possible to measure in both groups following the two interventions.
Placebo effect from exercise
We acknowledge that context effects (placebo) contribute to the treatment response from both surgery and exercise therapy. It is however well known that the size of the placebo effect is related to the invasiveness of interventions.5 If anything, context effects would speak in favor of surgery.
Muscle strength and functional tests as secondary outcomes
We believe it was both correct and valuable to include muscle strength as an outcome in this trial. Middle-aged patients with knee problems complain about symptoms, impaired function and, as a result, reduced quality of life. Improving physical impairments is thus a desirable outcome, not only from exercise therapy but also from knee surgery. While the pathway to improved muscle strength is direct following exercise therapy, it is believed that following surgery, when pain is reduced, patients will automatically resume their physical activities and thereby restore their muscle strength. While muscle strength is known to be impaired in patients prior to meniscal surgery6 and weak quadriceps muscle strength is a risk factor for developing osteoarthritis,7 high-level evidence on muscle strength following exercise therapy and meniscectomy were lacking.
By adding objective tests of muscle strength we could provide such evidence. Contrary to the common belief, patients were weaker at 3 months following surgery, a time point when patients are supposed to resume activities. This is worrying, considering that weak muscles are associated with more pain, less stability and more injuries. This is also worrying taking into account that at one year post-operatively muscle strength was barely improved compared to prior to surgery. We could also show that following a supervised 12-week exercise program muscle strength was maintained for a whole year, which is a promising finding.
References
1 Kise, N. J. et al. Exercise therapy versus arthroscopic partial meniscectomy for degenerative meniscal tear in middle aged patients: randomised controlled trial with two year follow-up. BMJ 354, i3740, doi:10.1136/bmj.i3740 (2016).
2 Roos, E. et al. ICRS Recommendation Document: Patient-reported outcome instruments for use in patients with articular cartilage defects. Cartilage 2, 122-136, doi:10.1177/1947603510391084 (2011).
3 Collins, N. J. et al. Knee Injury and Osteoarthritis Outcome Score (KOOS): systematic review and meta-analysis of measurement properties. Osteoarthritis Cartilage 24, 1317-1329, doi:10.1016/j.joca.2016.03.010 (2016).
4 van de Graaf, V. A., Wolterbeek, N., Scholtes, V. A., Mutsaerts, E. L. & Poolman, R. W. Reliability and Validity of the IKDC, KOOS, and WOMAC for Patients With Meniscal Injuries. Am J Sports Med 42, 1408-1416, doi:10.1177/0363546514524698 (2014).
5 Zou, K. et al. Examination of overall treatment effect and the proportion attributable to contextual effect in osteoarthritis: meta-analysis of randomised controlled trials. Ann Rheum Dis 75, 1964-1970, doi:10.1136/annrheumdis-2015-208387 (2016).
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Competing interests: No competing interests