by David Wadsworth
Why Persistent Pain is Hard to Treat – Missing Puzzle Piece Two
I can’t recall the number of times I have met someone new at my kid’s school, sports event or similar and as soon as they find out I am a physio they ask “I have a sore back - what causes that?” This is a fair enough question but one epitomising the common belief, even amongst some practitioners, that there is a single clear cause for a problem as difficult and complex as persistent spinal pain. This type of belief is relevant for acute pain caused by trauma, but has absolutely nothing to do with persistent pain, as we have shown throughout this series of posts on persistent pain.
Missing Puzzle Piece Two - Persistent Pain is Multifactorial in Origin.
The reality is that persistent pain is multifactorial in origin. This means there are multiple causes, not a single cause, and trying to accurately identify the specific set of causes for someone you have just met at in a social setting is impossible.
A major review of low back pain by authors Peter Kent and Jennifer Keating revealed that up to the year 2008 at least 1501 factors had been scientifically recognised as contributing factors to lower back pain and these are just the proven ones! Many more causes are yet to be proven or perhaps even identified.
Let’s look at a common and relatively simple (biomechanical) example to illustrate the concept of persistent pain being multifactorial in origin. Look at the runner in the picture (not the actual patient for privacy reasons). Imagine she has knee pain without swelling, a condition somewhat simpler than chronic back pain. Her pain is under the kneecap. She enjoys running for fitness and works at a desk. Her symptoms were of gradual onset related to running. As is typical of mechanical kneecap pain, she feels pain after running and after prolonged sitting. The pain improves with rest but recurs with running. Examining a patient with this problem typically demonstrates tenderness under the kneecap, and pain when loading the kneecap (eg. when performing a single leg squat). The diagnosis is known as “patellofemoral pain syndrome (PFPS)”, meaning that the joint formed between the kneecap (patella) and thigh bone (femur) is inflamed or painful from overload. As we mentioned in one of our earlier posts in this series, this is part one of her diagnosis: the “medical label” that we place on the condition.
Part two of the diagnosis is to identify the multiple causative factors that together have resulted in her pain. This is the most important part as it is what requires treatment.
With runners and PFPS, the cause is rarely in the knee itself (with the exception of those whose pain is caused purely from overtraining). Rather the knee is forced to move abnormally due to a problem in the foot, hip or even the spine, whereby the abnormal movement overloads the kneecap.
Look at the picture again. Notice that her knee rolls inwards when her foot hits the ground, which is abnormal as it should remain pointing straight ahead. There are multiple mechanical causes in both the hip (weak lateral gluteal muscles causing the knee to roll inwards and the pelvis to drop), and an over-pronating foot again causing the knee to roll inwards. An over-pronating foot (also known as a flat or planus foot type) requires more assessment as many things can cause a flattening of the foot arch when running. In this case the causes of her over-pronating foot included a tight calf (the foot rolls inwards or pronates during the second half of stance phase to compensate for the tight calf, dragging the tibia or shin bone with it which rolls the knee inwards). The other factor causing the foot to roll inwards was structural – her heel bone was inverted relative to the tibia which causes the foot to roll inwards to get the foot properly onto the ground (again dragging the tibia with it and causing the knee to roll inwards with it).
So now we have our two diagnoses:
So if we are going to sort this patients knee out and produce a lasting solution, guess what we need to target in our treatment? Her kneecap…. Not likely! You can tape her kneecap and strengthen her quads till the proverbial “cows come home” but the kneecap is not the cause, it’s the victim in this case. All you’d be doing is treating symptoms not causes and at best providing temporary relief. We really need to address the 3 main causes by considering treatments such as:
Failing to address all the elements causing the knee to roll in when running will still leave a level of mechanical overload that may cause her pain to recur, but addressing all of the key factors adequately will result in a lasting solution.
For all types of persistent pain, looking for the multiple underlying causes that are relevant for that individual’s problem is one of the keys to successful and lasting treatment results.