Effects of dietary intervention and quadriceps strengthening exercises on pain and function in overweight people with knee pain: randomised controlled trialBMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b3170 (Published 19 August 2009) Cite this as: BMJ 2009;339:b3170
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As a Consultant in Orthopaedics and Trauma with an interest in knee
surgery I was concerned about the method of recruitment of patients into
the otherwise excellent study by Jenkinson et al. Knee pain is a symptom
and not a diagnosis. My concerns are several. The first is that there must
be a number of confounding factors that could influence outcome in such a
small study. By including only patients over 45 years with a symptom of
knee pain into a trial of treatment options for osteoarthritis of the knee
there must have been patients with alternative diagnoses to end stage
Nothing in the study methodology attempts to identify the patient
with knee pain from osteoarthritis compared to patients with other causes
of knee pain.
Primary unicompartmental osteoarthritis of the knee can be the end
stage of the biomechanical consequences of a single initiating event. For
example an unstable meniscal tear leads to cyclic high pressure loading of
the adjacent hyaline cartilage. This leads to progressive degenerate
changes of the hyaline cartilage. Progressive degenerate changes of the
hyaline cartilage leads to progressive joint space narrowing, synovitis
and periarticular osteophytes, subchondral plate microfracture and
reactionary subchondral sclerosis and subchondral cyst formation. This
progression of events takes time. The localised high pressure as a result
of the meniscal tear is inversly proportional to a person's weight and
directly proportional to the size of the meniscal fragment. The failure of
any material depends on the load and number of cycles of loading
experinced by the material. Therefore, the time taken to progress healty
hyaline cartilage through degenerate change to osteoarthritis is inversly
proportional to the patients weight and the number of cycles of loading.
These biomechanical principles are well understood and established.
Knee pain in this single aetiological situation arises initially from
an unstable meniscal tear. Timely arthroscopic partial menesectomy
relieves knee pain completely. There is little evidence that these
patients treated in the early stage by arthroscopic surgery progress to
osteoarthritis. Therefore, my greatest concern about this study is that
patients with a treatable condition, a meniscal tear, were subject to a
treatment that would have hastened their degenerate changes towards
Osteoarthritis of the knee is an expensive condition to treat. As a
society we now need to look at the identification and prevention of this
condition rather than the expensive options for its treatment.
Competing interests: No competing interests
The article by Jenkinson et al1 provides yet more evidence that such a
simple, safe and low intervention has positive and gratifying results in
such a prevalent complaint.
In this unselected group, it is of interest to note that over half of
participants did not have radiological evidence of osteoarthritis. This is
a reminder of the low sensitivity of radiographs in the syndrome of knee
pain and does not represent a substitute for clinical examination.
Practitioners should always consider intra and peri-articular soft tissue
problems in addition to referred pain from other musculoskeletal regions.
Nevertheless, improvements were noted, irrespective of cause and in the
absence of obvious harm, with this simple intervention. Therefore, one
could postulate this considerable group with normal radiographs consists
of a spectrum of potentially self limiting soft tissue disorders skewing
the observed improvements. This question could be approached by interim
analysis of WOMAC pain scores and functioning in those with low Kellgren-
Lawrence scores at 6 or 12 months and, in doing so, define the
characteristics of a better prognostic group.
Similarly, in such a varied group, could one define a poorer
prognostic group? In previously published work2, Jenkinson et al’s group
have examined the role of muscle power and knee pain. Muscle strength was
significantly higher in the exercise group although baseline values not
presented3. One may expect higher WOMAC pain scores and, by extension,
lower muscle strength in the group with higher radiographic scores but
this caveat does not necessarily hold true. This grey relationship between
pain and radiographic change has been questioned for some time4, but the
evolution of MRI and representative findings raises further questions5.
Furthermore, muscle weakness may initiate and perpetuate the progression
of OA6 so to target muscle strength7 and weight loss in the group with low
pain scores but evident radiographic change may be a worthwhile
Finally, the implementation of such a brief intervention strategy
would be straightforward in a primary care or clinic setting. In the
longer term compliance is central to success. In a fashion akin to
salivary thiocyanate assays in smokers, could a quick bedside measure of
extensor strength be a modifiable and predictive surrogate for compliance
with an exercise programme alongside traditional measures such as weight
and blood pressure?
1. Jenkinson CM, Doherty M, Avery AJ, Read A, Taylor MA, Sach TH, et al.
Effects of dietary intervention and quadriceps strengthening exercises on
pain and function in overweight people with knee pain: randomised
controlled trial. BMJ 2009;339:b3170.
2. O'Reilly SC, Jones A, Muir KR, Doherty M. Quadriceps weakness in knee
osteoarthritis: the effect on pain and disability. Ann Rheum Dis
3. Thomas KS, Muir KR, Doherty M, Jones AC, O'Reilly SC, Bassey EJ. Home
based exercise programme for knee pain and knee osteoarthritis: randomised
controlled trial. BMJ 2002;325(7367):752.
4. Lawrence JS, Bremner JM, Bier F. Osteo-arthrosis. Prevalence in the
population and relationship between symptoms and x-ray changes. Ann Rheum
5. Wenham CY, Conaghan PG. Imaging the painful osteoarthritic knee joint:
what have we learned? Nat Clin Pract Rheumatol 2009;5(3):149-58.
6. Slemenda C, Brandt KD, Heilman DK, Mazzuca S, Braunstein EM, Katz BP,
et al. Quadriceps weakness and osteoarthritis of the knee. Ann Intern Med
7. Mikesky AE, Mazzuca SA, Brandt KD, Perkins SM, Damush T, Lane KA.
Effects of strength training on the incidence and progression of knee
osteoarthritis. Arthritis Rheum 2006;55(5):690-9.
Competing interests: No competing interests