The cyclist’s tricky hip – part one of three
The purpose of this post is to bring to light some experiences that I have had with fitting clients to bikes who have less than optimal hip or pelvis function. The issues that I will go over here will be in 3 parts;
Part 1; labral tears, CAM lesions and the arthritic hip
Part 2: the sticky, torsioned Sacro-iliac joint
Part 3: the assymetrical hip socket
The following is a brief summary and is aimed at health professionals and those with a keen interest in biomechanics, anatomy and human function. Some of the narrative is, unfortunately, necessarily technical and as such may not be fully accessible to the layperson. I have done my best to simplify what is, by necessity, a complicated subject. I have not been entirely successful.
Part 1; labral tears, CAM lesions and the arthritic hip
The hip joint comprises a ball and socket arrangement with smooth, hard cartilage on the surface of the “ball” and the “socket”. There is a flexible cartilaginous lip which extends from the edge of the socket and helps to enclose the ball of the hip – this structure is called the Labrum and assists with stability of the joint. Unfortunately, it is also prone to damage from either heavy blows to the hip, unusual pivoting movements, arthritic degeneration and from CAM lesions – small bony bumps on the edge of the ball of the hip which are thought to be reactive bone calluses – basically a chronic bone bruise from our younger years of sitting or exercising with our hips in extreme ranges of motion. The CAM lesion has multiple different forms and sizes, as does the labral tear ( https://www.methodistorthopedics.com/labral-tears-of-the-hip) that can result from, or cause, the lesion itself. The resultant impingement of the hip socket is termed FAI (Femoral-Acetabular impingement)
To avoid rehashing information that is already well covered elsewhere, I will direct your attention to a Wikipedia page which covers the topic nice and succinctly;
FAI is what happens when the edge of the hip socket starts rubbing on the edge of the femoral head. It can be present from the existence of a CAM lesion, a labral tear or from other arthritic changes at the hip joint. The actual pain from FAI is usually a deep anterior groin pain, but can present as a lateral hip pain, deep buttock pain or any combination of the above. The patient will usually show up as positive with a FAIR test or, less frequently, a FABER test. In my experience, the FAIR test is by far the best predictor of FAI.
FAIR test; https://www.youtube.com/watch?v=9Q9YdBke3Kc
FABER test; https://www.youtube.com/watch?v=xcIQDMQZilM
An adequate range of hip internal rotation (at 90 degrees of hip flexion) to ride a road bike with a moderately low torso position is typically anything over 20 degrees from the neutral position in the FAIR test. If the rider has less than 20 degrees of internal rotation available, there MAY be fallout on the bike from this. Normal external rotation range varies between the sexes, with women typically having more, but can range from 45 degrees through to 100 degrees or so for flexible hipped riders.
There are a variety of presentations that the rider may have when examined with the FAIR test;
1) Normal hip internal/external rotation bilaterally (symmetrical range of motion, no pain through the test and reasonable range of motion)
2) One side restricted into internal rotation with or without groin pain. If the restriction causes the rider’s internal rotation to fall below 20 degrees, there may be issues on-bike as the hip pulls up into flexion at the top of the stroke. If range gets below 10 degrees then there is almost certainly going to be fallout on the bike.
3) Both sides restricted similarly with or without pain
4) Both sides have the same overall range of motion, but the range of motion is distributed unevenly – more about this in Part 3
Now, that’s all well and good – you’ve got a rider who may or may not have FAI but have shown up positive in the test and are restricted with or without pain to less than 20 degrees of internal rotation (the test is not perfect and can throw up the odd false positive or negative) What now? Well, this is where it gets tricky – because often the rider will not be complaining of hip pain on the bike. Their issue may be knee pain, or lower back pain, or hot foot or….. the list goes on.
Why? Neurological hierarchies are often to blame here. The body has a system of determining if damage to a structure is occurring, or likely to occur in an overuse type situation like cycling. The more important that structure is to your overall health and wellbeing, and the less well that structure can absorb the unnatural, damaging loads, the more likely your nervous system is to shift the load somewhere else. We do this every day, in every facet of our movement patterns – we compensate for our inadequacies by shifting load somewhere else. We do it subconsciously, and so well that we are almost never aware of it. The hip is reasonably high up in the chain of importance – it’s a large weight bearing joint, close to your lumbar nerve plexus and of prime importance to your ongoing ability to stand, walk and run. If it were to become chronically inflamed, sustain a cartilage tear or other critical damage, it would catastrophically impact on the ability of the organism (you) to function and survive. Therefore, the logical choice for the rider, at a subconscious level, is to compensate and shift the load somewhere else.
The compensatory movement patterns that most frequently occur are (not exclusively) as follows;
1) The rider will kick their hip out at the top of the stroke as the knee comes up.
2) The muscles which control this kick are the deep external rotators in the back of the hip. The deep glutes – your piriformis, your gluteus minimus and your gluteus medius will become hypertonic (tight and overactive) from the fatigue of constantly changing the plane of motion of your hip to unload the FAI lesion. Often the hip flexor will become similarly tight.
3) The knee, being forced out laterally away from the midline, will be pulled back in to a “normal” position above the pedal as the hip descends back downward – this is never good for the knee.
4) The rider will drop one hip to further unload the affected side. Paradoxically, this can be either hip depending on how their nervous system copes with the issue.
The fallout is typically knee pain. The knee is a single-plane joint, with limited ability to function outside of its normal plane of motion. It does not cope well with being forced to act outside its natural parameters. I have also seen riders with FAI complaining of hot foot, calf cramps, Achilles tendinopathy, arch pain, low back pain and, sometimes even groin pain from the actual lesion itself (although this is, surprisingly, rare). A common one is recurrent gluteal trigger points and deep hamstring pain on the bike which resists all efforts to break down, and can result in a sticky, posteriorly rotated sacro-iliac joint (more on this in Part 2) .
The moral of the story is – if you are having trouble with a “stiff hip” and a poor plane of motion of one leg, seek help from a Physiotherapist or similar practitioner, or have a friend examine you to see if there are any potential FAI issues. A word of caution – it is remarkable how many health practitioners will either miss this issue, disregard its importance or fail to recognize the biomechanical ramifications. This is not always ignorance on their part – modern Physical therapists, Osteopaths and the like are not well educated on this topic (I know I wasn’t!) and, unless they have an enquiring mind and have figured this stuff out for themselves, many simply aren’t aware of the diagnostic tricks and pathological flow-on effects from FAI. You may need to find a better than average health professional simply to be diagnosed clearly.
The obvious question next is; what can we do about it on a bike? There are a few possibilities;
1) Space the rider’s feet apart further to lessen the amount of impingement occurring. This is, in my experience, more effective if both feet are spaced apart evenly (all other morphological assymetries aside) even if they only have one affected hip. On-bike symmetry is your friend!
2) Use shorter cranks. The shorter the crank arm, the lower the hip will rise into flexion at the top of the stroke, relieving hip impingement at the anterior aspect of the joint.
3) Lessen the torso angle of the rider. The more upright the rider, the less deep hip flexion – and therefore impingement – occurs.
4) In extreme cases – surgical intervention is warranted to clean out the labral tear and remove the cam lesion. One young Danish semi-pro friend of mine has recently had keyhole surgical intervention to remove a large CAM lesion with great success.
I hope that this write-up has been helpful for the other bike fitters out there who read this blog, and for riders who may be suffering from recalcitrant issues on the bike. Part 2 will deal with the common flow-on problem that comes with assymetrical hip function on the bike – a sticky, rotated sacro-iliac joint. Part 3 will deal with an uncommon presentation – assymetrical hip socket orientation.