By Leslie Rudzinski, PT OCS CFMT
As we all know, running is a compressive sport. Each time the runner’s foot hits the ground, the body weight is transferred down through the pelvis, into the stance leg, and ultimately to the foot. The laws of physics dictate that each time this happens, an equal and opposite ground reaction force is transmitted back up through the foot, to the leg, into the pelvis and on up the spine. In an efficient system where the base of support (that is, the foot) is healthy and the rest of the structure is aligned appropriately, the forces are distributed evenly throughout the system and breakdown is minimal. However, as soon as one segment in that system is not aligned properly, breakdown and injury are more likely to occur. We often talk about foot and knee trouble in the runner, now we’re going to tackle the pelvis.
The pelvis consists of two innominate bones each divided into three regions called the ilium, the ischium and the publis. The sacrum sits below the last lumbar vertebra and between these two innominate bones at the ilium which forms the two sacro-iliac (SI) joints. These joints in a sense connect the spine to the lower extremities. Each innominate bone moves independently during gait rotating forward and backward along with the legs. During forward and backward movements of the spine the two sides of the pelvis move together. The sacrum tilts forward and backward along with the spine and rotates right and left complimenting the pelvic motion during gait. Most pelvic dysfunctions occur when too much motion occurs at one of these SI joints, that is, it is a hypermobility problem rather than a hypomobility or stiffness/tightness problem.
What does an SI problem look like? Sacroiliac joint problems are almost always one sided. They can generate pain in the lower lumbar region, groin, buttock, hamstring region, or even in the pelvic floor and are usually aggravated by movement including running, walking and changing positions. If we go back to our evaluation of running and how the forces are transmitted through the body, we can see that if the pelvis is not aligned properly, breakdown can begin to occur. If one innominate bone, for example, is rotated too far forward at the time of impact, that innominate bone will take undo force and can become jammed in that position thus preventing backward movement. This can occur over time with repetition or may happen suddenly especially from running on uneven surfaces or as a result of “catching” oneself to prevent a fall.
Improper alignment during running is not the only thing that can contribute to SI problems. Muscle imbalance is another very important factor. A teacher of mine once said “If you’re symmetrically tight, be aware; but if you’re asymmetrically tight “BEWARE”. Assymetrical tightness can set people up for big problems. In the case of the SI, here are just a few examples. If one hamstring is a lot tighter than the other it can pull that innominate bone backwards resulting in a “Posterior Ilial Rotation”. A tight hip flexor (iliopsoas) can lead to an “Anterior Ilial Rotation”and a tight Piriformis can lead to a “Sacral Torsion” or rotation. Along with assymetrical tightness is often weakness of the antagonistic (or opposite) muscle. For example, if the iliopsoas muscle is very tight, its antagonist the gluteus maximus ,may be weak. These kind of imbalances in strength from one side to the other can also lead to SI problems.
If you think you might have an SI problem it is important to have a Physical Therapist evaluate you. Treatment of SI problems is very specific to the type of dysfunction present. Never try to self treat based on what worked for “the other guy’s” SI problem. The best way to lower your chances of getting an SI problem is to have a physical therapist evaluate your postural alignment and work on improving it. Also it is helpful to stretch out any assymetrical muscle tightness and strengthen the core and the gluteal muscles especially gluteus medius.