Journal article review of "Effects of strength training on the treatment of Patellofemoral pain syndrome -- a meta-analysis of randomized controlled trials"

In today's article we will critically review the following research paper:

Effects of strength training on the treatment of patellofemoral pain syndrome -- a meta-analysis of randomized controlled trials.

Cardoso RK, Caputo EL, Rombaldi AJ, Del Vecchio FB

Fisioterapia em Movimento [Physical Therapy in Movement] 2017 Apr-Jun;30(2):391-398

Link: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-51502017000200391&lng=en&tlng=en#B24

So what type of evidence is this article?

The below image shows where this article ranks in the hierarchy of evidence:

So this article comes under the second to top one: Other Systematic review & Meta-Analysis

What conclusion is made?

The authors concluded that strength training significantly helped Patellofemoral pain syndrome.

Are the conclusion’s justified by the data?

The reduction was purely of pain and so it is justified but other factors such as quality of life, functional ability, ability to go back to activity and sport weren’t looked at in this case, although they do mention 1 study in the introduction that did find improved function.

What is the article briefly saying?

Pain is significantly reduced in Patellofemoral pain syndrome with strength training that targets the Quadriceps, Hip abductors and Lateral hip rotators.

Is the purpose of the study clear and what is it?

Yes it is clear.  The purpose is to establish if pain can be reduced via strengthening type exercise for Patellofemoral pain syndrome to clinically significant margins as to inform clinical practice to include this type of approach.

Were the search methods used to locate relevant studies comprehensive?

They did an electronic search of randomised control trials, they looked at only pain and only excluded the adolescent only population studies. They found 39 relevant studies and with inclusion/exclusion criteria they included 5 studies, which isn’t a massive amount but they only looked at English and Portuguese studies, which would have slightly limited the included studies.  

Is it clear what was measured, how & what the outcomes were?

They simply measured pain at the start and at the end post intervention. So this is very clear and simple to understand.

Are the measurements valid, reliable & reproducible?

All studies except one used the Visual analogue scale (VAS) the other was the Numerical Pain Rating Scale (NPRS). The VAS is the most commonly utilised assessment for pain measurement and the Numerical Pain Rating Scale (NPRS) is very similar and both are considered valid, reproducible and reliable measures for pain.

Is the data suitable for analysis?

The data was analysed with the Stata 12.1 program, which is data analysis software. They used Cochran’s Q test to evaluate inter-study heterogeneity. They found 75% and reference that this indicates good heterogeneity based on the study referenced in relation to this. The outcomes were polled using the random effects model, which is fine for the type of data they were looking at.

The results indicated a positive effect with a probability of (p < 0.001), which is excellent.

Are results presented clearly & in sufficient detail to enable readers to make their own judgement?

The results are presented well to demonstrate the overall results with some good details to make sense of what was done in each study but the first table is confusing due to 6 studies being included not 5. Having said this, the reader can make a quick assessment of the effect of the specific exercises used in each study and see the actual effect.

Are results discussed in relation to existing knowledge? 

They relate their findings to studies previously done, which have found similar results. Some of this information is slightly debatable on occasion. For example talking about the Vastus Medialis Oblique (VMO) muscle being important, which is impossible to train independently and so irrelevant to add to the statement of training the Quads as a whole. Plus Song et al (2009) details that trying to target it made no difference. This finding is in keeping with the current thinking on the VMO.

Is the discussion biased?

In terms of bias, The main author has extensive qualifications in the field of exercise but seems to be focused on research. In this regard he has little to gain about the results going negative or positive.

Implications of the review for practice & research:

One of the included studies by Khayambashi et al (2012) used 20 plus repetitions per set, which isn’t considered optimal for strengthening. So it is very possible for even greater response with heavier loads and lower repetitions. Also in the study by Song et al (2009) they used good rep and set numbers for strength but it could be argued that only 2 minute rests were quite short for optimal strength gains. The overriding consensus though is that progressive strengthening lowers pain in patellofemoral pain syndrome but this doesn’t account for other broader variables. It is possible that this reduction in pain improves the chances of a return to normal activities. However if these participants are not doing their usual hobbies, for example football, then they may increase their pain again if they tried to do this. The types of exercises are very non-functional and so I believe that they are a good starting point to begin rehabilitation. Once this baseline strength is built then they will need further, more dynamic and functional rehabilitation to get pain free sport back to normal too. This review obviously doesn’t look at this but this would be a great follow up study to see what it would take to get back to full fitness without pain.

Conclusion:

Strengthening works for pain but may need to be developed further for full functional restoration. It is feasible to maybe get even greater benefits if they used more classic strengthening parameters rather than endurance ones. Further studies may be able to get more specific with the exercise types that are the most effective too but this is more difficult to do. So clinically it highlights the broad idea of including strengthening but it still is not super specific to give definitive guidelines to follow.