Leg Pain in Older Adults: Where Is It Coming From?Aches and pains seem to be part of the aging process for many people. Hip pain is especially common but doesn't always come from the hip so diagnosis can be tricky. Likewise, knee and lower leg pain must be evaluated carefully because the origin can be the lumbar spine or hip. Pain that begins in one body part or region but is felt somewhere else is called referred pain.
In this study from Chiba University, Graduate School of Medicine in Japan, orthopedic surgeons review 420 patient records looking for clues to sort out lower leg pain. With patients who have both lumbar spinal stenosis (narrowing of the spinal canal or openings for the spinal nerves) and hip joint osteoarthritis -- finding the origin of the pain can be a challenge.
They start by knowing that referred pain is always a possibility. So the patient's evaluation must include clinical tests that focus on the low back, hip, and knee. The surgeon knows the typical pain patterns but when there is pain along the lateral (outside away from the other leg) side of the lower leg requires some additional testing.
The surgeon has at his or her disposal imaging studies such as X-rays, myelograms, CT scans, and MRIs. These are helpful but when someone has both stenosis and hip osteoarthritis, it might be necessary to perform some nerve injections. In this study, of the 420 patients who had lower leg pain from lumbar spinal stenosis, only four had back or hip pain with lateral leg pain.
Those four patients received a lidocaine (a type of novocaine) injection around the spinal nerve at the L5 level. In all four cases, the pain went away. That might confirm the problem was coming from pressure on the L5 nerve root from the stenosis. Especially because they also received an injection of lidocaine into the hip joint without a change in their pain.
But surgery to remove bone from around the nerve and fuse the lumbar spine did NOT relieve their pain. These four patients did have hip pain but they also had low back and severe leg pain. Clinical tests of the hip (e.g., Patrick and Friberg tests) were negative. Tests for sciatica and vascular compromise (loss of blood supply to the lower leg) were also negative.
Six to 12 months later (without knowing for sure if the origin of the lower leg pain was coming from the hip), surgery was done to replace the diseased hip joint. And guess what? All four patients experienced complete and long-lasting pain relief. How do the surgeons explain these results?
Anatomic studies in animals have shown that messages via the L4 to S1 level nerves do go to the posterior area of the hip capsule. In other words, it is possible that hip joint pain is transmitted along the L5 spinal nerve. This may be why the spinal nerve injection at L5 relieved the pain.
But if the pain was really coming from the degenerated hip, then why didn't the lidocaine injection into the hip joint provide pain relief? The authors do not know but suspect perhaps there are central mechanisms, a term used to describe pain messages that are transferred via the spinal cord to the brain. Once the pain message is sent along this pathway, the body doesn't seem to know how to turn the message off -- even when pressure is
removed from the nerve.
The authors conclude by suggesting that lower leg pain can be a challenge to diagnose and treat effectively in older adults who have both lumbar spinal stenosis and hip osteoarthritic degenerative changes. Either or both problems can cause referred pain to the lateral lower leg area. Step-by-step evaluation is recommended with conservative care first before considering surgery. The decision to do surgery (lumbar spine decompression versus hip replacement) remains a challenge without clear guidelines to follow.
Junya Saito, MD, et al. Difficulty of Diagnosing the Origin of Lower Leg Pain in Patients with Both Lumbar Spinal Stenosis and Hip Joint Osteoarthritis. In Spine. December 1, 2012. Vol. 37. No. 25. Pp. 2089-2083.
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