Osteoarthritis is the leading cause of hip replacement, accounting for roughly 60% of all procedures. But several other conditions can damage the hip joint severely enough to require surgery, from autoimmune diseases to bone injuries to problems people are born with. In every case, the underlying issue is the same: the joint has deteriorated to the point where pain can no longer be managed with medication, physical therapy, or lifestyle changes.
Osteoarthritis and Cartilage Breakdown
The hip is a ball-and-socket joint lined with a layer of smooth cartilage that lets the bones glide against each other. In osteoarthritis, that cartilage wears away over time. As it thins, the body tries to repair the damage by growing new bone around the joint edges (called bone spurs) and thickening the bone underneath the cartilage. These changes don’t restore normal function. Instead, they make the joint stiffer, more painful, and less mobile.
Eventually the cartilage can wear down completely, leaving bone grinding directly against bone. At that stage, the joint space visible on an X-ray narrows dramatically, and everyday activities like walking, climbing stairs, or getting out of a chair become painful or impossible. Osteoarthritis tends to develop gradually over years or decades, and it’s the single most common reason people end up needing a new hip.
Rheumatoid Arthritis and Autoimmune Damage
Unlike osteoarthritis, which is driven by mechanical wear, rheumatoid arthritis is an autoimmune condition where the body’s immune system attacks the lining of the joint. The inflamed tissue swells and thickens, producing enzymes that eat away at cartilage and bone from the inside. Specialized cells called giant cells actively break down bone fragments, accelerating destruction far faster than normal wear would.
Rheumatoid arthritis accounts for about 3% of hip replacements in younger adults. The destruction can be severe and rapid, sometimes progressing over months rather than years. When inflammation medications and immune-suppressing drugs can’t halt the damage, replacement surgery restores mobility and relieves pain effectively.
Avascular Necrosis: Loss of Blood Supply
The ball at the top of the thighbone (the femoral head) depends on a delicate network of blood vessels to keep its bone cells alive. When that blood supply gets cut off, the bone cells die and the femoral head gradually collapses. This condition, called avascular necrosis or osteonecrosis, is the second most common reason for hip replacement in people under 45, responsible for about 24% of procedures in that age group.
There are two main pathways to avascular necrosis. The first is trauma: a hip fracture or dislocation can physically tear the blood vessels feeding the femoral head, cutting off supply instantly. The second is non-traumatic, and two risk factors dominate. Long-term use of corticosteroids (commonly prescribed for asthma, lupus, and other inflammatory conditions) and heavy alcohol use together account for more than 80% of non-traumatic cases. In some people, no clear cause is ever identified.
Once the femoral head starts to collapse, the smooth spherical surface becomes irregular, cartilage breaks down rapidly, and pain intensifies. Early-stage cases can sometimes be managed with procedures that try to preserve the natural joint, but advanced collapse typically requires full replacement.
Hip Fractures and Post-Traumatic Arthritis
A serious hip fracture doesn’t just heal and return to normal. Even after surgical repair, the joint surface may be left slightly uneven, and the cartilage that was compressed or cracked during the injury begins to deteriorate. At least one in four people who fracture their hip socket develop osteoarthritis afterward. The timeline varies widely: some people develop significant arthritis within two to five years, while others remain functional for decades before the joint wears out.
Post-traumatic arthritis was the indication for about 4% of hip replacements in younger patients. Car accidents, falls from height, and sports injuries are the most common culprits. The younger you are when the injury occurs, the more years the damaged joint has to deteriorate, which is one reason hip replacements in younger adults have been rising.
Developmental Hip Dysplasia
Some people are born with a hip socket that’s too shallow to fully cover the femoral head. This condition, called developmental dysplasia, may go undiagnosed in childhood and only cause problems in adulthood. Because the socket doesn’t cradle the ball properly, the contact area between the two bones is smaller than normal. That concentrates all the body’s weight onto a narrow strip of cartilage along the rim of the socket, wearing it down much faster than it would in a normally shaped joint.
Over time, this abnormal stress leads to secondary osteoarthritis, often decades earlier than the typical age for hip arthritis. Adults with untreated dysplasia may need hip replacement in their 30s, 40s, or 50s, well before the age when most people develop joint problems.
Ankylosing Spondylitis
Ankylosing spondylitis is a type of inflammatory arthritis that primarily affects the spine but frequently involves the hips as well. Chronic inflammation in the hip joint can erode cartilage and, in severe cases, cause the joint to fuse with new bone growth. When the spine is already stiff from the disease, losing hip mobility on top of that can be profoundly disabling. Hip replacement in these patients restores a critical range of motion that the spine can no longer compensate for.
Paget’s Disease and Other Metabolic Conditions
Paget’s disease causes bone to break down and rebuild abnormally, producing bones that are larger, softer, and misshapen. When it affects the pelvis or upper thighbone, the altered bone structure changes how forces travel through the hip joint. The result is excess stress on the cartilage, which accelerates the development of osteoarthritis. Hip pain from Paget’s disease is initially managed with bone-strengthening medications, but if arthritis progresses, surgery becomes necessary.
When Replacement Becomes the Answer
Regardless of the underlying cause, the decision to proceed with hip replacement follows a consistent pattern. The three criteria that surgeons and guidelines rely on are persistent pain that hasn’t responded to conservative treatment, loss of daily function (difficulty walking, sleeping, or performing basic tasks), and X-ray evidence of significant joint damage such as narrowed joint space, bone spurs, or cysts.
Conservative treatment is always the first step. That typically includes pain medication, physical therapy, activity modification, walking aids, and weight loss if applicable. Surgery enters the conversation only after those approaches have been given a reasonable trial and failed to provide adequate relief. There is no specific age cutoff or lab value that triggers a replacement. It comes down to how much the joint damage is affecting your life.
Rising Rates in Younger Adults
Hip replacement was once considered a procedure for people in their 70s and 80s, but the demographics have shifted considerably. Between 2000 and 2010, the rate of hip replacement in people aged 45 to 54 more than doubled, rising from 45 to 117 procedures per 100,000 people. That age group saw a 205% increase, the largest of any demographic. Meanwhile, the share of replacements performed on people 65 and older actually decreased.
Several factors are driving this trend. Higher rates of obesity put more stress on hip joints earlier in life. More active lifestyles lead to more sports injuries and post-traumatic arthritis. Improved implant durability has also made surgeons more willing to operate on younger patients, since modern artificial hips last longer than previous generations of implants. Younger patients also tend to recover faster, with average hospital stays of about three days for the 45-to-54 age group.