Part 2 – The sticky, torsioned sacro-iliac joint
Part one described common traumatic and non-traumatic lesions that occur in the hip joint, particularly CAM lesions and labral tears. The purpose of this section is to describe one of the natural sequelae of functioning with a dodgy hip socket or a CAM lesion – a posteriorly torsioned sacro-iliac joint. But first, some anatomy;
The sacro-iliac joints are two load-bearing joints that form the pelvic girdle. Together with the pubic symphysis at the front of the pelvis, the SIJ’s are able to rotate forwards and backwards slightly as you walk, run or cycle and thus contribute to normal lumbar spine and hip movement. We call the complicated motion of the SIJ’s “nutation” rather than pure rotation but for our purposes we’ll stick with rotation as it’s conceptually easier to imagine. The two SIJ’s are remarkably strong, stable joints termed a “diarthrosis” and are surrounded by tough ligaments which bind them together. Critically, the inner contacting surfaces of the joints are rough and knurled – much like a spline on a piece of machinery – meaning they mechanically lock together under load to help stabilize themselves.
As you walk, run or pedal, the SIJ’s float forwards and backwards slightly in a rotatory manner. This is all well and good except when the person has either a heavy traumatic injury to the joint such as a severe fall, or when they have been functioning for a long time with a tighter, larger gluteal complex. An example will help to visualize what goes on here, as this is actually what happened to me some years ago!
Rider NS is a structurally symmetrical rider of average ability at best. He is set up with a particularly poor bike position by a fitting system which shall remain nameless. It turns out that his saddle is some 60mm too high and under anything except moderate load, he drops his heels massively and over-extends both knees violently. Subconsciously his nervous system has an in-built protective mechanism which protects his dominant right leg, so he begins riding with a large right hip drop to allow the right leg to reach the pedal effectively. This causes a resulting lift of the left hip and the left leg suffers the brunt of the compensation. To add to his difficulties, he has small CAM lesions with slight hip impingement which his nervous system knows about and does its best to unload by externally rotating the leg at the top of the stroke (as mentioned in part one).
Over some years he becomes larger, stronger and much tighter in the left hip and gluteal complex due to the asymmetry of function. Power meter balance will later tell him that he’s developing 57% of his 20 minute power output with his left leg and 43% with his right leg. His quadriceps and hamstring will, after many years of compensation, measure 12mm more in circumference than his right leg. Similarly, his left glute is much larger and stronger than the right side. The CAM lesion further increases the load on his already struggling left glute. Eventually, the uneven load on his left SIJ pulls the joint into a semi-permanent posteriorly rotated position and his compensation strategies run out – left gluteal, hamstring and knee pain starts to kick in and he is suddenly unable to ride more than 10km without severe pain.
This is a real-life example of improper bike position causing severe asymmetry and physical pain. His inappropriate saddle height combined with his CAM lesions led to a long, slow build up of gluteal tension which eventually pulled the left SIJ into a backwards torsion and resulted in pain. This is a remarkably common pattern although the causative factor isn’t always cycling – it could be a labrum tear, a shorter leg, and old injury, a large pelvic tilt or anything which is causing the rider to bear uneven weight on one leg or function assymetrically for a long period. The result is a sticky, posteriorly torsioned SIJ. The rider will usually present with knee pain but occasionally lower back or hip pain (our rider above had all three in various forms).
This is the tricky part of the problem. Many a physio, chiro, osteopath, doctor etc has missed this issue as the torsion is often quite subtle. We can be talking about a 2-3 degree rotation in the joint which is not always terribly evident upon examination. A high level of manual dexterity is often needed to feel these issues. I use a combination of a few basic tests to ascertain if the SIJ is stuck in posterior rotation, or is merely stiff into anterior rotation. (Note that is is possible to have an anterior rotation or upslip/downslip but these are comparatively very rare in my experience)
1) Palpate the two SIJ’s in standing and lying posture. Lying down prone is usually much clearer as you remove other postural distortions from the equation. If one Posterior Superior Iliac Spine is sitting proud of the pelvis, there may be a torsion (or an anatomical asymmetry of the PSIS!
2) Gillette’s test. Have the patient stand in front of your on one leg. They should lift the other leg up and down towards their chest 2-3 times. Place one thumb on the centre of the sacrum and one thumb on the Posterior Superior Iliac Spine of the moving SIJ as it rotates forwards and backwards. Repeat on the other side and assess the degree of movement. The dodgy SIJ will often rotate backwards significantly less than the other side as it is already stuck in posterior rotation!
3) Lie the patient prone and place one hand on their PSIS, and lift the leg into extension. Assess the degree to which the SIJ rotates anteriorly and compare to the unaffected side. This video shows a manipulation at the end which is one of the treatment techniques – but the assessment of the magnitude of movement is the critical part for our purposes;
Assuming that you’ve identified that one SIJ is stuck in posterior rotation, the patient should now be treated for the condition. Common effective treatment for this issue usually involves heavy sustained muscle releasing to the hip flexor, quadriceps and gluteal complex with deep dry needling particularly for the gluteals to allow them to “release” their grip on the SIJ. The patient is usually softened up with soft tissue releases before manipulation is attempted. Multiple treatments are almost always required. Identifying the defect is tricky, removing it and keeping it under control can be a long and arduous process depending on how long it’s been there for and how assymetrical the rider has become. Often there will need to be specific strength training required for the opposite leg, and sustained treatment and stretching to help the SIJ unlock itself long-term and allow the rider to drift back towards reasonable symmetry.
In terms of on-bike issues, the rider will virtually never sit squarely no matter what you manage to do to their position. The hip simply cannot rotate normally when the SIJ is twisted backwards like this. They will typically kick the knee out to the side at the top of the stroke and present with knee pain on the affected side. The nature of the torsion means that as the SIJ pulls backwards, the plane of motion of the hip, and therefore the knee, are affected adversely – I’ve even seen riders with Achilles tendon pain from compensating by pointing the toe on that leg as their only symptom! Temporarily, a shim stack under the functionally shorter leg will help to improve symmetry on the bike but the rider will never be “right” until the SIJ is sorted out. This is one of those tricky issues which, unless identified, will plague the rider perpetually until it is identified and removed. Proper treatment off-bike is absolutely necessary.
This concludes part 2 of our “Tricky Hip” series. Part 3 will focus on the assymetrical hip socket – a reasonably rare congenital issue which results two hip sockets positioned differently in the pelvis but with identical range of motion.