Anatomical and biomechanical reminder
The tensor fascia lata muscle is a muscle of the pelvic girdle that unites the lower limb to the trunk. It is a small, elongated and thin muscle located on the external and superficial face, at the top of the thigh. In this, it is close to the gluteal muscles as far as the function is common. This action is mainly the abduction of the thigh (training the lower limb outside) and incidentally the flexion of the hip (training the thigh on the trunk).
The gluteus maximus and tensor fascia lata muscles form a unit called the gluteal deltoid. The gluteus maximus and the tensor fascia lata both unite on the band of Maissiat, called the iliotibial tract. This strip or tract descends all along the thigh, on its lateral face (such as the seam of the pants) and ends on the very upper part of the leg, on the tibia (Gerdy's tubercle).
As a result, this set also plays a role in stabilizing the knee, especially when it is bent. This is an essential element.
The pathology
Fascia lata syndrome or ilio tibial band syndrome or windshield wiper syndrome is due to friction of the ilio tibial tract (tendon of the fascia lata) on the bone (the tuberosity of the lateral condyle of the femur), for repeated flexions and extensions of the knee. It is the repetition of movements that is the cause of the pain. This is pain on the lateral (external) side of the knee. Of course, many other diagnoses must be ruled out when faced with external knee pain in athletes. But the peculiarity of fascia lata syndrome is the appearance of pain specifically in running. Indeed, it is not uncommon to see a footballer who does not complain of any knee pain when practicing his sport and to see this same footballer complain of external knee pain only while jogging. . This particularity should guide the doctor towards this typical conflict of the band against the external condyle of the femur. It is essentially running that is the cause of this syndrome (cycling, regularly cited, only very rarely causes this pathology).
The pains are generally very reproducible, that is to say that it is the same painful sensation, for the same running time. After stopping running, the pain stops or may persist for a few hours in daily life, especially on stairs.
The syndrome can sometimes be bilateral
This is pain in the terminal portion of the fascia lata tendon, but it is not a real tendinopathy. In fact, the tendon is completely healthy. It is only an irritation of the tendon, on the external condyle of the knee, by repeated movements. It is therefore a tendon-bone conflict. But the tendon, it is repeated, is normal without structural, fibrillar abnormality, ….
Let's take a comparison with the foot and the shoe: if the shoe is too small, there will be a foot-shoe conflict, which will generate foot pain. But the foot is healthy, it will be “painful but not sick”. It is exactly the same for the fascia lata, there is no tendinous lesion within it as can be seen, for example, for the Achilles tendon or the patellar tendon. Moreover, this tendon never breaks, so no fear at this level. I reassure the runner who suffers...
Clinical examination focuses on ruling out all other causes of external (lateral) knee pain. Despite everything, the history of the pain (only in running and not in football, cf. above example) and especially its reproduction during flexion-extension, under load, of the knee between 20 and 30°, are often sufficient to confirm the diagnosis. Obviously, the freedom of the hip and the knee is sought, the axis of the lower limbs (research genu varum) is not forgotten.
The key examination, to affirm that it is a conflict between the fascia lata and the femoral bone, is ultrasound. As we have said, it is not a chronic lesion of the tendon, so the latter is strictly normal, in imaging. We are essentially looking for a bursitis (fluid pocket) between the bone and the tendon. This bursitis confirms the conflict.
For some authors, this serous bursa is isolated and for others, it is an extension of the lateral synovial recess (small cavity with nourishing liquid for the cartilage) of the knee joint. This liquid bursitis may not be seen on MRI because this examination is done with the knee in extension (the bursitis is then compressed, therefore not visible). Ultrasound, made with the knee slightly bent, without pressing the probe (so as not to compress the bursitis) is a better examination. This ultrasound should always be done immediately after training for running (i.e. i.e. at the moment of pain) to clearly visualize the bursa. This fluid pocket may possibly be punctured and infiltrated, under ultrasound control.
The causes ?
The big question is to know why a runner, overnight, without any obvious reason, without any rational explanation, starts this disease. It is not uncommon to meet marathon runners, who have made a heavy preparation, who have run their marathon, without any pain in the knee and who, after 10 to 15 days of rest, restarting running, develop this syndrome, with its attendant pain.
Why ?
Admittedly, running is almost solely responsible for this syndrome, but its appearance is often very whimsical, as seen in this classic example.
Does the morphology of an athlete change overnight?
Does his running technique suddenly change? …
As always, we must remain humble because no scientific study gives the answers. We do not know, currently, with certainty, why a runner develops this conflict nor, moreover, why he recovers from it (because recovery always happens).
There are, of course, risk factors that are well identified, such as:
Intrinsic factors:
-the genu varum (anomaly of the lower limbs which are "in brackets"; the knees which do not touch each other)
- the tuberosity of the external condyle too bulky (bone deformation)
- the leg axis not aligned (internal rotation or external rotation)
-the varus of the rear foot (turned towards the axis of the body, i.e. inside)
- unequal length of the lower limbs
But, as we can see, all these intrinsic factors (morphology acquired from the end of puberty) were present well before the pain and will persist after recovery. These are, moreover, simple constitutional abnormalities, very frequent, which can be found in many athletes, even in those who do not suffer or will never suffer from the wiper syndrome. So let's be careful about "morphological explanations"
Extrinsic factors:
- the stiffness of the fascia lata
-disharmony between adductors and hip abductors
- a practice of running, on curved roads, always running on the same side
It can be seen that all of these risk factors (intrinsic + extrinsic) cannot explain the onset of the disease. Moreover, these are only risk factors (therefore hypotheses) and not scientifically proven causes.
One day, the tendon-bone conflict sets in; once this inflammation has started, the slightest solicitation, of the same type, will re-activate it. It's a bit like the fire in the forest, the slightest breath of wind reactivates the fire that we thought was extinguished... but the fire always ends up going out... the runner will always heal...
Therapeutic proposals
The causes of the appearance of a windshield wiper syndrome are not well defined, nor is the treatment. Do not expect a unique and "miraculous" solution to this pain.
It is therefore necessary to take a series of measures:
- do not let the pain set in (extinguish the fire from the start!); as soon as the runner feels discomfort on the outside of the knee, he must adapt his training:
- run on flat ground (no uphill or downhill)
-run in the middle of the road (if the roadway is curved)
- shorten the stride
-do not train for too long; stop before the pain becomes too great (know the time of onset of pain)
- apply ice, systematically, after sports practice
These few instructions are imperative but strict sports rest is not essential. In addition, one can move towards support sports (tennis, badminton, football, handball, etc.).
Of course, the onset of pain requires reconsidering certain technical elements:
1. Do the shoes fit well? Is there abnormal wear? It is not the only cause but the correction of a static disorder can be useful; it obviously seems logical to reduce the conflict that exists, in dynamics, between the tendon and the knee. The prescription of a plantar orthosis (orthopedic sole) can then be justified. But I insist, it is not a miracle solution because we must always ask the following question "Why, before the onset of pain, this static disorder was in no way pathological?" »
2. Do fascia lata stretches? It is illusory because this tendon (bands of Maissia) stretches little. Nevertheless, stretching all the muscles of the lower limb should not be neglected.
3. Decrease local inflammation (because inflammation does exist)? We can use anti-inflammatories in the form of a gel, anti-inflammatories in physiotherapy (kinesitherapy), oral anti-inflammatories (medication by mouth), mesotherapy, etc. The best drug treatment remains puncture-infiltration of the bursitis which signs the conflict between the tendon and the bone (this gesture must be made under ultrasound control).
4. When you've tried everything and you're still in pain? It is then necessary to return to the fundamentals of biomechanics. The pain is due to a conflict between a tendon and a bone. But it's not really a statics problem; this is a dynamic problem. It is therefore always necessary to think dynamically and not statically. This conflict is highly dependent on the angle of flexion of the knee: the more the runner flexes the knee, the greater the risk of friction between the tendon and the bone. Conversely, the runner who bends the knee little is less likely to trigger this irritation, inflammation. It is clear that it is necessary to run on flat ground, by reducing the strides (but being able to increase their frequency). However, minimalist shoes require the runner to shorten the stride: is this a solution? I don't know, and no scientific study says so, but the question deserves to be asked, especially for the runner who has tried everything, without success.
Conclusion
The wiper syndrome is a pathology of conflict, tendon-bone, essentially due to running (support sports do not generate this syndrome). There is not a single cause but rather a set of factors that trigger this external knee pain. It is certainly necessary to adapt and personalize your sports practice during the painful period rather than waiting for a miracle medical or paramedical solution. Static disorders often have a "good back" when it is essentially a dynamic, repetition problem.
