By Dr. Geoffrey Modest
2 cohort studies (the Framingham Osteoarthritis Study, a local community-based study, and the Osteoarthritis Initiative, a multicenter longitudinal study, assessed the correlation between hip pain and x-ray findings for hip osteoarthritis, or OA (see doi:10.1136/bmj.h5983).
- Framingham Study: 946 ambulatory individuals >50yorecruited in 2002-5. All had hip x-rays, and those with hip pain pointed to where they had hip pain on a visual hip representation, the frequency of the pain, and they were examined for pain with internal rotation. Mean age 63.5, 56% women, 93% white, BMI 28, frequent hip pain in 13% though only 4% with pain in the groin or anterior thigh
- Osteoarthritis Initiative: 4366 ambulatory people who had or were at risk for knee OA. All had hip films and if they had pain, had the visual hip representation to localize the pain, questions about frequency of pain but no examination. Mean age 61, 58% women, 80% white, BMI 28, 16% with frequent hip pain though only 4.5% in the groin or anterior thigh
- Framingham data:
- 6% of those with hip pain had x-ray evidence of OA
- 7% of those with hip OA on x-ray had frequently painful hips
- Sensitivity of x-ray diagnosis of OA for hip pain localized to groin was 36.7%; specificity was 90.5%, positive predictive value was 6.0% and negative predictive value was 98.9%
- Osteoarthritis Initiative data:
- 1% of those with hip pain had x-ray evidence of OA
- 8% of those with hip OA on x-ray had frequently painful hips
- Sensitivity of x-ray diagnosis of OA for hip pain localized to groin was 16.5%; specificity was 94.0%, positive predictive value was 7.1% and negative predictive value was 97.6%
So, there are several issues here:
- For those with hip pain which is typical for arthritis, there is a poor correlation with x-ray And, this goes both ways: pain not related to x-ray changes and x-ray changes not related to pain. BUT, there is no clear gold standard for the definition of hip OA, a bit of a problem, though those with classic anterior groin pain worse with internal rotation and flexion seem like pretty good candidates for the diagnosis (and x-ray is not, since so many people have bad rays without significant symptoms).
- A related issue is the lack of concordance between knee pain and x-rayUsing the NHANES I database, including 6880 people aged 25-74, there was also significant discordance between symptoms of knee pain and x-rays: radiographic stage 2-4 OA was found in 319 subjects (3.7%) and only 47% of these people had knee pain; knee pain was reported by 1004 people (14.6%) and only 15% had radiographic stage 2-4 changes of OA (see J Rheum 2000;27:1513-7). A recent analysis found that those with clinical knee pain but low OA grade on x-rays had heightened pain sensitivity (measured by Quantitative Sensory Testing, assessing pressure-pain thresholds at affected and unaffected sites to repeated and sustained stimuli) while those with low pain scores but high grade OA on x-ray were significantly less pain-sensitive, even after adjusting for age, sex, race, and psychosocial measures including depression, anxiety, pain catastrophizing (their word, not mine) and sleep disturbance (see Arthritis Rheum 2013; 65(2):.doi:10.1002/art.34646)
- What does this mean?
- We still may want to get hip x-rays in those with pain, to rule out osteonecrosis, transient osteoporosis, metastatic disease; and consider referred pain (though should not be reproducible by direct pressure/manipulation).
- Pain is a funny thing. There clearly is not a one-to-one correspondence between pain and anatomic x-ray Lots of other factors play a role (including stress, sleep deprivation, depression, social supports, trauma history etc.)
- So, we should not dismiss the diagnosis of hip OA based on normal or near-normal x-rays. The treatment is pretty much the same whether there are x-ray changes or not (weight loss, PT, pain meds). But the lack of x-ray changes should not dissuade us from the diagnosis of OA, nor potentially beneficial treatments (including intra-articular steroid injections)
- But if the patient does have normal x-rays, I think it makes sense to review the history and PE to make sure that OA is still the likely diagnosis (as an aside regarding knee pain, I have had several patients sent to me for knee injections for OA, which on my exam has really been anserine bursitis. They still got an injection, but in a different place…. so, it makes sense to me to re-evaluate the pain when there is discordance of findings, just to be sure)
- And it is not superclear what the role of MRI is. There is no question from the literature that MRI is more sensitive than x-ray, but likely is much less specific (this is pretty clear for knees, less clear for hips). But that being said, in those with significant functional impairment, clear indications that the pain is from the hip but only minimal arthritic changes on pain film, I would consider further workup for possible inflammatory synovitis, MRI to make sure it is not early osteonecrosis/avascular necrosis (if history of steroids, alcohol, pancreatitis, hemoglobinopathies, etc.) since early intervention (core decompression) can avoid later total hip replacement surgery, and consider MRI arthroscopy especially to look for labral tears, which are typically degenerative in those >50 yo and not responsive to conservative management.