Advanced Degeneration of the Pelvis and Hips
Advanced degeneration of the hip means the cartilage lining the ball-and-socket joint has worn away substantially, leaving bone moving against bone. It is among the most common causes of disability in older adults, and it has a distinctive presentation that is frequently misread: hip arthritis typically causes pain in the groin rather than over the side of the hip, and it very commonly refers pain to the knee—so much so that some people present complaining only of knee pain. Degeneration also affects the joints at the back of the pelvis and the pubic joint at the front, though these behave differently. Hip replacement, where it becomes necessary, is among the most reliably successful operations in medicine.
What is it?
The hip is a ball-and-socket joint formed by the rounded head of the thigh bone sitting within a cup-shaped socket in the pelvis. Both surfaces are covered with cartilage, and a rim of fibrous tissue called the labrum deepens the socket and helps seal the joint. The design allows movement in all directions while carrying several times body weight with each step.
Degeneration means this cartilage has progressively worn away. The joint space narrows, bone beneath the surface thickens and develops cysts, bone spurs form around the margins, and the capsule tightens. As the cartilage layer is lost the leg effectively shortens, and movement becomes restricted—characteristically rotation first, then the ability to bring the knee toward the chest.
The pelvis contains other joints that also degenerate, and they behave differently. The sacroiliac joints, where the spine meets the pelvis at the back, develop degenerative changes with age in the great majority of people, and these are usually asymptomatic—reports describing sacroiliac degeneration frequently describe a normal finding for age. The pubic joint at the front of the pelvis similarly shows age-related change that is usually silent, though it can become painful after childbirth, in athletes, and in specific conditions.
The understanding of why hips wear out has changed substantially, and this is the most interesting development in the field.
Hip arthritis was long described as primary—arising without identifiable cause—in the majority of cases. Current evidence suggests that a substantial proportion of these cases are in fact secondary to subtle abnormalities of hip shape that have been present since adolescence and concentrate load abnormally over decades.
Femoroacetabular impingement describes a mismatch between the ball and socket in which they collide at the extremes of movement. In the cam type, the head of the thigh bone is not perfectly round, and the non-spherical portion jams into the socket on bending and rotating, shearing the cartilage at the rim. In the pincer type, the socket is too deep or over-covers the head, pinching the labrum. Both are common, both frequently cause no symptoms for years, and both are associated with the development of arthritis in later life. Cam-type shape is more common in men and in those who played high-impact sport during adolescence while the growth plate was open.
Developmental dysplasia describes a socket that is too shallow, so that load is concentrated over a smaller area of cartilage at the rim. It ranges from severe forms identified in infancy to mild forms that are never detected until arthritis develops in the thirties or forties. It is more common in women.
Recognising these patterns matters because they explain why some people develop hip arthritis unusually young, and because intervening before cartilage is destroyed can alter the course.
Other causes are well defined.
Avascular necrosis occurs when the blood supply to the head of the thigh bone is interrupted, causing the bone to die and subsequently collapse. Causes include corticosteroid use, excess alcohol, previous hip fracture or dislocation, sickle cell disease, and radiotherapy, though a proportion occur without identifiable cause. It typically affects younger adults and progresses quickly once collapse begins, which is why early recognition on MRI matters.
Previous fracture involving the joint surface, and childhood conditions including Perthes disease and slipped upper femoral epiphysis, leave deformity that predisposes to later degeneration.
Inflammatory arthritis, particularly rheumatoid arthritis and ankylosing spondylitis, affects the hip through a different mechanism.
Obesity and heavy physical work increase risk, though the association with the hip is weaker than with the knee.
The symptom pattern is distinctive, and understanding it prevents a common diagnostic error.
Groin pain is the hallmark. Hip joint pain is felt in the groin, often deep and aching, sometimes described as a band across the front of the hip. It is provoked by weight bearing and walking and relieved by rest, at least initially.
Pain referred to the knee is common and clinically important. The hip joint and the knee share nerve supply, so hip disease frequently produces pain felt in the thigh and knee. Some people present complaining only of knee pain, with an entirely normal knee on examination and imaging. Any assessment of knee pain should include examination of the hip, and this is a recognised source of delayed diagnosis.
Pain over the outer side of the hip is usually not the hip joint. That area corresponds to the greater trochanter, and pain there typically arises from the tendons and bursa in that region—a separate condition often called greater trochanteric pain syndrome—rather than from joint degeneration. People frequently point to the side of the hip and are investigated for arthritis, when the problem lies in the soft tissues.
Stiffness is worst on first standing and eases over a few minutes.
Loss of movement follows a characteristic sequence, with rotation lost earliest. The practical consequences are often noticed before pain becomes severe: difficulty putting on socks and shoes, reaching the toenails, getting in and out of a car, and sitting cross-legged. Many people date their problem from when these tasks became awkward.
A limp develops, often with the body leaning toward the affected side to reduce load.
Night pain and rest pain develop in advanced disease and are among the strongest indicators that replacement should be considered.
Diagnosis combines examination with imaging.
Examination assesses gait, leg length, and the range of movement, with rotation tested with the hip bent. Pain reproduced at the limits of rotation points to the joint. Specific tests assess for impingement and for pain arising from the trochanteric region rather than the joint.
Weight-bearing X-rays of the pelvis are the primary investigation. A standing front view of the whole pelvis allows both hips to be compared, assesses the joint space under load, and shows the shape of the socket and the head of the thigh bone, which identifies underlying dysplasia or impingement. A lateral view of the affected hip adds further detail.
The features of degeneration are joint space narrowing, bone spurs, hardening of bone beneath the joint surface, and cysts. Loss of joint space at the top of the joint is typical of degeneration, while loss toward the inner side raises the possibility of inflammatory arthritis.
MRI is used where X-rays are normal or near-normal but symptoms persist. It is the test of choice for avascular necrosis, which it detects long before any change appears on X-ray—this is important, since treatment options are far better before the bone collapses. It also identifies stress fractures, labral tears, and soft tissue causes of pain, and demonstrates the cartilage directly.
CT shows bone detail and is used for planning surgery, particularly where deformity is complex.
Injection of local anaesthetic into the joint under imaging guidance is a valuable diagnostic step. Where pain is substantially relieved, the joint is confirmed as the source. Where it is not, pain is arising elsewhere—from the spine, the trochanteric soft tissues, or elsewhere in the pelvis—and treating the hip would not help. Referred pain from the lumbar spine is a particularly common alternative, and distinguishing the two is a frequent clinical question in older people who have degenerative changes in both areas.
Important to Know
Hip arthritis responds well to treatment at both ends of the spectrum: non-surgical measures help considerably in earlier disease, and hip replacement is one of the most reliably successful operations in medicine for advanced disease. Care is managed by primary care clinicians, physiotherapists, and orthopaedic surgeons.
Exercise is effective and should be the foundation of non-surgical management. Programmes combining strengthening of the muscles around the hip and pelvis, aerobic activity, and stretching to maintain movement improve pain and function, and the benefit is well supported. As with the knee, exercising an arthritic hip does not accelerate wear, and avoiding activity leads to weakness and stiffness that worsen the situation.
Weight management reduces load meaningfully, with forces through the hip during walking several times body weight.
A walking stick used in the hand opposite the affected hip reduces the force through the joint substantially—more than most people expect—by changing the lever arm the muscles must work against. It is frequently resisted on grounds of appearance and is one of the most effective simple interventions available.
Anti-inflammatory medication helps, with topical preparations less effective for the hip than the knee because the joint lies deeper. Oral anti-inflammatories are used at the lowest effective dose given their stomach, kidney, and cardiovascular risks. Paracetamol has limited efficacy. Opioids are not recommended for osteoarthritis.
Corticosteroid injection into the hip is performed under imaging guidance, since the joint cannot be reliably entered blind. It provides temporary relief and serves a useful diagnostic purpose. Some evidence suggests an association between injection and subsequent rapid joint destruction in a small number of cases, so repeated injections are approached with some caution, particularly in the hip.
Joint-preserving surgery is relevant for younger people with structural abnormality before degeneration becomes advanced. Arthroscopic surgery reshapes the bone in femoroacetabular impingement and repairs the labrum, and periacetabular osteotomy repositions a shallow socket in dysplasia. Both aim to improve mechanics and delay or prevent arthritis, and both are considerably less effective once cartilage has already been substantially lost. This is the main argument for recognising these conditions early, and for a younger person with hip pain to be assessed for underlying shape abnormality rather than simply reassured.
Hip replacement is the definitive treatment for advanced disease and deserves its reputation. Pain relief is reliable, satisfaction is high—consistently higher than for knee replacement—function improves substantially, and modern implants last well, with the majority surviving beyond twenty years. It is frequently described as one of the most successful operations in medicine, and the description is justified.
Timing is a genuine judgement. The usual guidance is that replacement is appropriate when pain persists despite proper non-surgical treatment and is limiting daily activities and sleep, rather than being dictated by the X-ray. Operating too early in a young person means facing revision later; waiting too long allows muscle weakness, deformity, and deconditioning that make recovery harder. Waiting until the pain becomes unbearable is not advantageous, and delaying excessively is associated with worse outcomes.
Approaches to hip replacement differ and are frequently discussed online. Anterior, lateral, and posterior approaches each have advocates, with differences in early recovery and dislocation risk but broadly similar outcomes by a year. The surgeon’s familiarity with their chosen approach matters more than the approach itself.
Recovery is quicker than many expect, with most people walking with aids within a day or two and resuming most activities over six to twelve weeks. High-impact activity is generally discouraged long-term to protect the implant, but walking, cycling, swimming, and golf are typically encouraged.
Hip resurfacing is an alternative in selected younger men, preserving more bone, though its use has narrowed considerably following problems with certain metal-on-metal designs, and it is now performed in specific circumstances by experienced surgeons.
Several conditions commonly confused with hip arthritis deserve mention, since treating the wrong structure is a frequent problem.
Pain over the outer hip is usually greater trochanteric pain syndrome, arising from the gluteal tendons and bursa. It responds to physiotherapy addressing tendon loading rather than to anything directed at the joint.
Referred pain from the lower spine commonly produces buttock and thigh pain and coexists with hip degeneration in older people. Distinguishing the two determines which treatment helps, and a diagnostic injection is often the most efficient way to resolve it.
Avascular necrosis should be considered in anyone with hip pain and relevant risk factors, particularly corticosteroid use, since MRI detects it before X-ray changes appear and early treatment options are far better than late ones.
In older people, particularly those with osteoporosis, a hip fracture can present with groin pain and inability to weight bear after minimal or no trauma, and may not be visible on initial X-rays, requiring MRI.
Sacroiliac degeneration reported on imaging in an older person is usually an incidental age-related finding. Where sacroiliac pain is genuinely suspected, particularly in a younger person with inflammatory features, a different set of conditions including ankylosing spondylitis should be considered.
Care is managed by primary care, physiotherapy, and orthopaedics. Imaging should be weight-bearing where possible, and findings are considered alongside symptoms and function rather than in isolation, since X-ray severity correlates only loosely with how much a person is affected.
Patient education plays an important role. Understanding that hip pain is felt in the groin rather than the outer hip, that it commonly refers to the knee, that exercise helps and does not accelerate wear, that a walking stick in the opposite hand genuinely reduces load, that hip replacement is highly successful, and that younger people with hip pain should be assessed for underlying shape abnormality all contribute to appropriate care.
Red flag symptoms include inability to bear weight after a fall or minor injury, which may indicate fracture even where X-rays initially appear normal; a hot, swollen, acutely painful hip with fever, which may indicate joint infection and requires urgent assessment; sudden severe hip pain in someone taking corticosteroids or with other risk factors for avascular necrosis; unexplained weight loss, night sweats, or a history of cancer alongside bone pain; progressive neurological symptoms in the leg, including weakness or numbness, suggesting a spinal cause; calf pain with swelling, redness, or breathlessness, which may indicate a blood clot; and rest or night pain that is severe and unrelenting. These warrant prompt medical evaluation.