Differentiating Hip vs Lower Back Pathology
By J. Rafe Sales, M.D. & Co-Director of Providence Brain and Spine Institute's Spine Services
Hip pain is a common and disabling condition that affects patients of all ages and that providers encounter frequently, especially in primary care settings. In one study, 14.3% of adults 60 years and older reported significant “hip” pain on most days during the previous six weeks. The differential diagnosis of hip pain is broad, presenting a diagnostic challenge for even the most experienced clinician. Therefore having a well-established protocol to differentiate where the pain is originating can be very helpful in determining the next step in treatment.
The first step in evaluating the patient is a thorough history. Clinicians must determine whether a patient has pain with activity, at rest, or both. Pain at night, and the presence or absence of pain-free intervals, may indicate a tumor or an infection. In general, difficulty with putting on shoes is associated with hip issues. A burning or electric sensation that extends to the knee or foot is more suggestive of lumbar spine issues, especially if accompanied by numbness or weakness. The ability of a patient to ambulate more successfully with a bent posture, a.k.a. the “shopping cart sign,” or improvement in pain when sitting, may indicate lumbar stenosis.
In my practice, the most important question to ask relates to the location of the patient’s so-called “hip pain.” A patient will often express that their pain is localized to one of three regions: the anterior hip and groin, the posterior hip and buttock, or the lateral hip (Figure 1). Anterior hip and groin pain is commonly associated with intra-articular pathology of the hip itself, and allows the clinician to focus on the hip. This pain can be caused by an issue as simple as hip arthritis or as complex as a labral tear.
Posterior hip or buttock pain typically has a greater variation of possible causes. This can be as simple as a hamstring strain or as complex as sacroiliac joint dysfunction or spinal nerve compression. Lateral hip pain occurs with greater trochanteric pain, but can also be seen with lumbar radiculopathy or a soft tissue strain.
The second key is a thorough physical examination. Palpation for areas of tenderness over the greater trochanter, sacroiliac joints, groin, buttock, and lumbar spine may provide clues to the more likely pain generator. Pain directly over the lateral hip is almost always trochanteric bursitis, and can be treated with anti-inflammatory medications and reassurance.
Hip range of motion testing should be performed, assessing for loss of rotation with pain at terminal range of motion. This is done by placing the patient supine and flexing their hip to 90 degrees, then rotating the lower leg in and out. Limited internal rotation in the presence of groin pain means the patient is 14 times more likely to have the pain arising in the hip joint. While in that same position, I will push down on the knee with significant force. If this causes pain in the back of the buttock then that could be more suggestive of sacroiliac (SI) issues.
Positive provocative tests that likely indicate lumbar spine problems include the straight leg raise. If the pain radiates down the affected limb when the leg is raised off the table, it is an indicator of nerve impingement. Significant numbness or limb weakness is also suggestive of nerve compression in the spine.
Once the history and exam are completed, the next step is based upon the clinician’s judgment. If the clinician feels the hip is the source of the pain, a simple standing AP radiograph of the pelvis is often sufficient to identify hip arthritis. If the patient has failed to improve with significant physical therapy, then an orthopaedic surgery referral is often warranted. With the hip, sometimes an MRI-arthrogram is necessary and a standard hip MRI is not adequate; therefore, a timely referral may save the patient time and money.
Alternatively, if the pain is resulting from the spine or sacroiliac joint, then a standing AP and lateral lumbar radiograph is a good starting point. If the pain radiates down the leg and there is a concern for nerve compression, a standard lumbar MRI without contrast is usually sufficient.
By utilizing these simple tools, over 95% of cases can be differentiated and the appropriate treatment provided. If there is still a question as to the source of the pain or there is a concern about a rapidly declining patient, then a referral to an orthopedic surgeon or spine surgeon can always be utilized for advanced testing and treatment.
Figure 1: Location of Hip Pain- Anterior view left, posterior view right