Leg pains: sciatica explained

I get it all the time. People who come into my practice and tell me they have "sciatica". Occasionally they are right, often they are wrong. People tend to think that any pain in the leg that may relate to low back injury is "sciatica", some people even come in with no leg pain and just back pain who call it "sciatica". I guess it is time for me to show my benevolent side and educate the world at large.

 

So light up that Upmann No.2, throw a couple of fingers of Wild Turkey Rare Breed Bourbon into the glass and prepare to absorb the facts on sciatica.

 

Definition: Sciatica is pain in the legs or buttocks due to irritation or injury to the sciatic nerve or its nerve roots.

 

"I can see clearly now the rain has gone". Simpson, do you like that one? Your era not mine.

 

OK. So sciatica relates solely to the sciatic nerve. Suppose its time I told you the story of the sciatic nerve then.

 

The sciatic nerve is composed of roots leaving the vertebral column at the levels L4, L5, S1, S2 and S3 (see diagram). These join together to form a single nerve (true sciatic), it forms below the piriformis muscle and at this point is roughly the size of your thumb, deep in the gluteals and emerges into the buttock lying on the ischium bone of the pelvis. The sciatic nerve passes into the posterior thigh and supplies the hamstring muscles with their ability to function, the nerve continues to just above and behind the knee where it splits in two parts known as the peroneal and tibial components. These are known as the common peroneal and tibial nerves.

 

The common peroneal nerve supplies the lateral leg muscles below the knee as the superficial peroneal nerve and supplies the anterolateral lower leg muscles as the deep peroneal nerve. The tibial nerve supplies the posterior leg muscle (gastrocnemius and soleus) as well as the plantar (sole) foot muscles.

 

Generally "sciatic" pain related to low back injury is caused by compression (eg disc bulge) or irritation (eg arthritic compromise) of the nerve at the spinal levels L4, L5 and S1.

 

Usually sciatica is described as pain, but if more serious may also involve muscle weakness or sensory loss (numbness). You can identify the level of compromise or injury by the area affected. L4 shows as weakness to the hamstrings, L5 weakness is characterised by weakness to extensor hallicis longus (look it up!) S1 compromise will show a decrease in ankle jerk reflex and/or calf weakness. Sensory loss is examined by, for example, numbness on the inner low calf/leg (L4), numbness to the lateral calf/leg (L5), top of the foot (S1).

 

OK, I've finished my Upmann No.2 and two bourbons. Try it and you will know how long it took me to write this far.

 

Significantly, we find most sciatic pain is increased by flexion of the lumbar spine. You know what I mean, pain increases when you bend forward, such as putting on the socks and shoes in the morning or by trying T-Bar rows. The surgeon and researcher Kuslich demonstrated that sciatic pain could only be produced upon pressure or compromise of an already irritated nerve. You don't get sciatica from compressing a normal or non-irritated nerve. Oh yes, don't stick your "vitamin B" shot into it, you may need peeling off the ceiling afterwards.

 

If this is the type of pain or problems you are experiencing then I recommend you see a physiotherapist who specialises in spinal and/or sports areas. Don't leave it to chance.

 

 

Illustrations courtesy of the Bartleby.com edition of Henry Gray's Anatomy of the Human Body as adapted from original engravings from the 1918 edition (Philadelphia: Lea & Febiger, 1918).