There are probably more than 600,000 total hip replacements performed in the U.S. each year, with the leading cause for surgery being osteoarthritis (OA). OA is characterized primarily by degeneration and loss of articular cartilage; diagnosis is typically via X-ray. Pain from hip osteoarthritis can manifest in a range of locations, including the lateral hip, groin, buttocks, thigh, knee, and even the lower leg. Many people with hip osteoarthritis visible on X-rays do not have symptoms. The prevalence of hip osteoarthritis increases with age. One study of a county in North Carolina estimated the overall lifetime risk of developing symptomatic radiographic OA to be 25%.
I’m not a medical professional, and I'm not offering medical advice. You should consult with a physician or other qualified medical professional for diagnosis, treatment, and advice. The content on this site is for informational purposes only.
If you’re facing a total hip replacement, you’re certainly not alone. Estimates of the number of hip replacements performed each year in the US range from 544,000 to 605,000 to 760,000. A recent analysis found there were nearly 600,000 primary total hip replacements in 2022, counting just Medicare cases alone. Total annual volume in the US is projected to exceed 2 million by 2040.
The leading cause of first-time hip replacements is osteoarthritis, accounting for 71% of cases in the US, and 88% of cases in Australia and the UK. Fractures are the second most common cause, accounting for 21% of US cases and 6% of Australian cases. Other conditions that can lead to a total hip replacement include rheumatoid arthritis, post-traumatic arthritis, avascular necrosis, dysplasia, bone or cartilage cancer, and unrepairable labral tears.
Aside: In the UK and Australia, hip fractures are more often treated with partial hip replacements, rather than total. That explains why fractures are a lower percentage of total replacements in those countries compared to the U.S. and why osteoarthritis is a higher percentage.
Sources: UK data are from the “National Joint Registry 2025 Annual Report,” p. 45. Australian figures are calculated from Table HT10 of the “Australian Orthopaedic Association National Joint Replacement Registry 2024 Annual Report,” p. 150.
Osteoarthritis (OA) is the most common type of arthritis in the US, affecting 12% of adults over 20, and 33% of adults over 65.
OA is characterized by the progressive loss of cartilage and the progressive development of osteophytes (bone spurs), subchondral sclerosis (thickening of the bone directly below the cartilage), and subchondral cysts (fluid-filled spaces in the bone near the joint surfaces).
A simplified causal story is that the loss of cartilage increases pressure on the layers of the bones directly under the thinning cartilage, which causes them to thicken. When they thicken, they become less elastic and more brittle, leading to microfractures allowing joint fluid to be forced into the bone, forming cysts. The thickening of the subchondral layer also means it flexes less, putting even more stress on the remaining cartilage, which contributes to its degeneration, thus causing a vicious cycle. In addition, thinning cartilage leads to joint instability, which triggers the development of bone spurs at the edges of the joint — basically a reaction to new pressure resulting from the instability.
Over time, cartilage may wear away entirely, leading to bone-on-bone contact. As OA progresses, the joint becomes increasingly inflamed, stiff, and painful.
According to the American Association of Orthopedic Surgeons (AAOS), the most common symptom of hip osteoarthritis is pain.
There’s a lot of variance in where such pain manifests. While the AAOS states that pain is most commonly felt in the groin, some studies have found higher prevalence around the greater trochanter (the prominence on the outside top of the femur) and in the buttocks.
The AAOS does note that pain may be felt in the thigh and may radiate to the buttock or knee. However, they do not mention that pain may also be felt below the knee, a fact that several studies have found.
I frequently experienced lateral calf pain, a hip OA symptom I could only find documented specifically in one study. Fortunately, as with the patients in the study, my pain completely resolved after my hip replacement.
The AAOS also notes that pain may be worse in the morning or after sitting, and that pain may increase with vigorous activity. Neither of those were true in my case, even though I had severe, end-stage OA.
Here’s the very good news from a 2012 study:
“Regardless of the different pain patterns, 97.3% (110 of 113) of patients reported complete pain relief within 12 weeks after THA.”
Osteoarthritis that can be seen on an X-ray is called “radiographic osteoarthritis.” There are two widely used scales for grading the severity of radiographic osteoarthritis.
The first is the Kellgren-Lawrence (KL) scale.
The second is the Tönnis scale.
Reading X-rays is subjective. Five surgeons reviewed my images, and their individual descriptions of my joint space loss formed a continuum: moderate, marked, severe, complete, and bone-on-bone. Regardless, all but one classified my hip as KL Grade 4 or Tönnis Grade 3. (One gave it a KL Grade 3, which I found curious since he also described it as “bone-on-bone.” A typo, perhaps?)
Analyses of data from three major longitudinal studies have found that radiographic hip osteoarthritis is not a good predictor of pain.
In the Osteoarthritis Initiative and Framingham Study, the association was weakest: less than 25% of those with X-rays showing hip osteoarthritis experienced frequent pain, and less than 8% felt pain in the groin — the pain location most commonly associated with hip OA.
Even in the CHECK study, which specifically followed patients who were already experiencing joint pain or stiffness in at least one hip or knee, only 48.2% of hips showing osteoarthritis on X-ray were frequently painful.
The poor predictive value of X-rays might be because they are unable to discern more precise features, like subchondral bone marrow lesions.
Now that we understand the difference between radiographic OA and symptomatic (painful) OA, we can look at some prevalence data.
A 2014 study of Framingham, Massachusetts adults aged 50 and older found that 19.6% showed radiographic evidence of hip OA, though only 4.2% actually experienced symptoms.
A 2009 analysis of adults aged 45 and older in a North Carolina county found higher rates: 28% for radiographic hip OA and 10% for symptomatic hip OA (radiographic OA + symptoms).
The Framingham study found that men had nearly twice the rate of both radiographic and symptomatic hip OA compared to women (24.7% vs.13.6%; and 5.2% vs. 3%), though only the radiographic difference was statistically significant.
In contrast, the North Carolina study found that women had slightly higher prevalence of both radiographic OA (men 25%, women 30%) and symptomatic OA (men 8%, women 11%). Those differences were statistically significant.
A 2023 systematic review found no statistically significant difference globally between prevalence in men (9.42%) and women (7.94%).
Finally, a 2018 primer claims that men have a higher prevalence of hip OA before age 50, whereas women have a higher prevalence thereafter. That claim is based on a study from 1998, which I am unable to access and verify.
A separate analysis of the North Carolina data estimated an overall lifetime risk for symptomatic hip OA at 25.3%. The risks were estimated to be 18.5% for men and 28.6% for women, and 50% for those with a self-report hip injury vs. 22% for those without. Such differences, however, were not found to be statistically significant. In fact, the authors concluded that lifetime risk was similar by sex, race, educational level, hip injury history, and BMI. To be clear, these estimates were for the specific population in that North Carolina county. The authors explicitly recommend caution in generalizing the results to the entire US.
Two systematic reviews, one in 2008 and the other in 2023, found that prevalence of radiographic hip OA increased with age for both men and women.
The same correlation can be seen in the age-grouped North Carolina data (Table 2). For radiographic OA, the prevalence by age groups was 45-54 (21.2%), 55-64 (23%), 65-74 (31.1%), 75+ (42.9%). For symptomatic OA: 45-54 (5.9%), 55-64 (8.9%), 65-74 (10.8%), 75+ (17%). The trend can also be seen in the Framingham data (Table 1).
A follow-up analysis of the North Carolina cohort again demonstrated the progressive nature of hip OA. In the initial 1991–1997 data collection, the average age of participants was 61, the prevalence of radiographic hip OA was 28%, and the prevalence of symptomatic hip OA was 10%. Approximately 20 years later (2017–2018), the average age of the remaining original participants was 73.5, the prevalence of radiographic OA had risen to 53%, and the prevalence of symptomatic OA had risen to 18%.
A 2002 study of over 1,500 men and women aged 60–89 years old living in Beijing found just 1% showed radiographic OA, with no men and just 1 woman having symptomatic OA.
A 2023 systematic review found prevalence of radiographic hip OA was lowest in Africa (1.20%), followed by Asia (4.26%) and North America (7.95%), and highest in Europe (12.59%). The review speculated on possible causes ranging from genetic differences (greater build) to anatomical differences (lower rates of dysplasia in Asian countries, deeper acetabula in Europe), to lifestyle differences (high-fat, high-sugar Western diets, greater participation in high-risk and high-impact sports).
- - -
Posted April 2026.