Sacro-iliac Joint

When sciatica is not sciatica… 

Low back pain is a very common condition. It sometimes spreads to the leg, and is generally known as “sciatica”. Originally the term was meant to indicate that there was pressure on the sciatic nerve, and symptoms; mainly pain, tingling and weakness, were present in the regions supplied by the sciatic nerve. 

The most common cause of sciatica was/is; compression from a herniated disc, most commonly the L5/S1 disc. 

The good news with the diagnosis of sciatica is that most patients get better within three months, and no surgery is required. One year later it makes no difference whether you had surgery for the disc hernia or not. The initial swelling from inflamed disc tissue settles over the weeks, and therefore the compression on the nerve eases, and with it the symptoms. 

Many people believe they have sciatica when they experience symptoms of back pain and leg pain (namely pain in the buttock and back of the thigh).  In the majority of cases, the symptoms are not due to pressure on the sciatic nerve, but from other conditions, like hamstring problems, and the sacro-iliac joint that does not function as it should. 

What is the sacro-iliac joint? 

The sacrum (tail bone) and the two hip bones (iliac or innominate bone) from the pelvis, and the two sacroiliac joints are located at the bottom of either side of the spine, above the buttocks. 

Their function is to protect the pelvic organs. In addition, the transfer load (weight) from the trunk to the legs and vice versa. For this they need to stiffen up. But they also need a minimum of movement to absorb torsion, for instance when we walk. Otherwise we would walk like A2D2, the Star Wars companion to Luke Skywalker. 

This requires  strategies to adapt to the different situations. It is achieved in several ways. The surfaces of the joints match each other, there are strong ligaments between the two bones, and several muscles contract to provide stiffness; these are the deep muscles of the “core”. The integrity of the ligaments and the timing of the muscles activity combine to provide the required amount of pressure across the joint to fulfil its functions. If any of them fails, over time other muscles take over, the joint locks in the wrong direction and  the result is lower back pain, that spreads to the buttock and the thigh (back and side). 

The usual cause of these symptoms can be a fall, or a series of falls on the buttocks, as well as repeated jumps, landings, repetitive lifting and car accidents. Rear end collisions with one’s car stationary (at a traffic light, for instance) are typical. It can take months, even years to develop symptoms, because we have many mechanisms to compensate. When we “run out of compensation” symptoms appear. 

The diagnosis; we call it sacro-iliac joint incompetence-is made by history, clinical examination, and more recently with a new imaging technique, called SPECT-CT, a combination of low dose limited CT and a bone scan. While it involves a small amount of radiation, it is the only imaging technique that will identify problems in the biomechanics of the pelvis, and the overuse of the alternative compensation t=strategies (hamstring, adductor and gluteal tendon changes).

Treatment is usually with a very targeted exercise programme to improve timing  and endurance of the “right” muscles. It begins with very simple, “nothing to it”, exercises to activate the deep core muscles and develop endurance, before it builds up with other muscles and activities. 

In a personal series of more than 1200 patients, 75% to 80% improved with these exercises, under the direction of an experienced physiotherapist. The rest may require proliferative injections into the deep ligaments of the joint. Very rarely (less that 1%) surgery is required to fuse the joint. 

In summary, not every “sciatica” is real sciatica. Sacro-iliac joint problems are more common than originally thought (up to 20-25% of cases of low back pain), but most of them respond to specific exercise therapy.

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