It commonly causes groin pain that radiates down the front of the thigh, stiffness, pain at night, and can often limit your daily activities. It is often characterised by exacerbations and remissions and usually gets worse with time. It can worsen with activities that put the hip into flexion, such as sitting in low chairs and exercises like squats, lunges, and even riding a bike.
A standing X-ray is normally all that is required to make the diagnosis, and often more advanced imaging modalities like MRI scans can cause more confusion than help with the diagnosis.
The severity of arthritis on the X-ray does not determine what the management should be. This is based on the severity of your symptoms. The old saying in orthopaedics is "treat the patient, don't treat the X-ray."
What is happening in the joint
The hip is a ball-and-socket joint. The ball is the head of the femur; the socket is the acetabulum, a cup in the pelvis. Both are lined with articular cartilage, a smooth layer a few millimetres thick that lets the joint move almost without friction and spreads the load passing through it.
Osteoarthritis is the progressive loss of that surface. As cartilage thins, the bone beneath takes load it was not built for. It thickens in response, bony spurs called osteophytes form around the joint margins, and the lining and capsule become inflamed and tight, which is what makes the hip stiff as well as sore.
"Wear and tear" is the usual description and it is somewhat misleading. Osteoarthritis is not simple erosion from use. It is an active process involving cartilage, bone, the joint lining and surrounding tissues, and the body's response to the damage is part of what produces the symptoms.
Osteoarthritis versus inflammatory arthritis
Osteoarthritis is a degenerative condition and is far more common than inflammatory arthritis. It affects approximately 10% of the population. It becomes much more common as we age and is more common in females. Osteoarthritis causes thinning of the cartilage overlying the bone. As this process progresses, it can often lead to a point where there is virtually no cartilage overlying the bone. This is sometimes described as bone-on-bone arthritis.
Inflammatory arthritis is a condition that causes inflammation in the lining of the joint. There are a vast number of inflammatory arthritic conditions, with the most commonly known being rheumatoid arthritis. It often presents in multiple joints and is classically associated with significant swelling. If left untreated, this can result in secondary osteoarthritis. These days, rheumatologists can manage inflammatory arthritis extremely well with various medications, so early diagnosis is important. There is often a strong family history.
What causes it
Most hip osteoarthritis has no single identifiable cause. It develops gradually, usually after fifty, and family history makes it more likely.
Some develops because of an underlying problem with the shape or health of the joint, femoroacetabular impingement, hip dysplasia, avascular necrosis, previous fracture involving the joint surface, or a childhood hip condition such as Perthes disease. These are covered in the questions below.
Body weight matters, because the hip carries several times body weight with each step. Ordinary exercise does not cause arthritis.
How it is diagnosed
From the history, the examination and a plain X-ray.
The standard investigation is a weight-bearing X-ray of the pelvis, taken standing rather than lying down. Cartilage does not show on an X-ray, so it is assessed indirectly by the space between ball and socket. That space narrows as cartilage is lost, and the narrowing shows most clearly when the joint is loaded. This is why the film is taken standing, and why a lying-down X-ray can underestimate the changes.
Four features are looked for: narrowing of the joint space, thickening of the bone beneath the surface, osteophytes at the margins, and small cysts within the bone.
An MRI is not usually required. It may be arranged where the diagnosis is unclear, where symptoms do not match the X-ray, or where avascular necrosis, a labral tear or a stress fracture is suspected.
Why the X-ray and your symptoms often disagree
This causes a great deal of confusion, so it is worth being explicit.
Some people have marked changes on X-ray and modest symptoms. Others have significant pain with relatively mild change. The relationship between what the film shows and how the hip feels is genuinely loose.
Decisions are therefore based on symptoms and function, not on the X-ray alone. A film that looks worse than last year does not by itself mean anything needs to change. How far you can walk, and whether you are sleeping, matter more.
The old principle in orthopaedics is to treat the patient, not the X-ray.
How it progresses
Hip arthritis is a disease characterized by exacerbations and remissions. Sometimes it's really bad, sometimes it is not so bad. It is a degenerative condition, however, and usually gets worse with time.
Some people remain stable for years with modest symptoms. Others deteriorate more quickly. Symptoms also fluctuate, painful periods followed by quieter phases are normal, and a bad month does not necessarily mean the condition has changed. Decisions are best made on the trend across a year rather than on a single flare.
Most people with hip arthritis do not have surgery. The first question is not usually whether to have an operation, but how to manage the condition well.
What happens next
Treatment is staged. Exercise therapy, weight management where relevant, activity modification and appropriate pain relief come first, and are effective for many people. Injections have a limited but real role. Surgery is considered when symptoms persist despite these and the effect on daily life justifies an operation.
Each of these is covered in What to Try Before Surgery.
Common questions
What is the difference between osteoarthritis and rheumatoid arthritis?
Osteoarthritis is a degenerative condition in which the cartilage lining a joint gradually wears away, usually affecting one or a few joints. Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the joint lining, typically affecting many joints on both sides of the body, and is managed medically by a rheumatologist in the first instance.
Why is the X-ray taken standing up?
Cartilage does not appear on an X-ray, so its loss is assessed indirectly by measuring the space between ball and socket. That space narrows most visibly when the joint is bearing weight. A film taken lying down can therefore underestimate how much cartilage has been lost, which is why a standing X-ray is the standard investigation.
Do I need an MRI?
Straightforward hip osteoarthritis is diagnosed on a weight-bearing X-ray and does not usually require an MRI. An MRI may be requested where the diagnosis is uncertain, where symptoms do not match the X-ray findings, or where a condition such as avascular necrosis, a labral tear or a stress fracture is suspected.
My X-ray looks bad but my pain is manageable. What does that mean?
X-ray appearance and symptoms often do not match. Some people have marked changes on imaging with modest pain, and others have significant pain with relatively mild changes. Treatment decisions are based on how much the hip is affecting your daily life rather than on the severity of the X-ray alone.
Does hip arthritis always get worse?
Hip osteoarthritis generally progresses over time, but the rate varies considerably and is difficult to predict. Some people remain stable for years with modest symptoms; others deteriorate more quickly. Symptoms also fluctuate, with painful periods followed by quieter phases, so decisions are based on the overall trend rather than a single bad month.
What is femoroacetabular impingement?
Femoroacetabular impingement is a condition in which the ball and socket are shaped so that they catch against one another during movement. It typically causes groin pain in younger, active adults, particularly on deep bending or rotation, and over years it can damage the cartilage and lead to osteoarthritis.
What is hip dysplasia?
Hip dysplasia describes a hip socket that is shallower than normal, so the load passing through the joint is concentrated over a smaller area of cartilage. It is often present from childhood but may not cause symptoms until early adulthood, and it is a recognised cause of osteoarthritis developing at a younger age than usual.
What is avascular necrosis of the hip?
Avascular necrosis occurs when the blood supply to the head of the femur is interrupted and part of the bone dies and can collapse. Causes include high-dose corticosteroid use, heavy alcohol intake, previous fracture and some medical conditions, though sometimes no cause is identified. It is diagnosed on MRI when X-rays appear normal.
Common questions.
What is the difference between osteoarthritis and rheumatoid arthritis?
Osteoarthritis is a degenerative condition in which the cartilage lining a joint gradually wears away, usually affecting one or a few joints. Rheumatoid arthritis is an autoimmune disease in which the immune system attacks the joint lining, typically affecting many joints on both sides of the body, and is managed medically by a rheumatologist in the first instance.
Why is the X-ray taken standing up?
Cartilage does not appear on an X-ray, so its loss is assessed indirectly by measuring the space between ball and socket. That space narrows most visibly when the joint is bearing weight. A film taken lying down can therefore underestimate how much cartilage has been lost, which is why a standing X-ray is the standard investigation.
Do I need an MRI?
Straightforward hip osteoarthritis is diagnosed on a weight-bearing X-ray and does not usually require an MRI. An MRI may be requested where the diagnosis is uncertain, where symptoms do not match the X-ray findings, or where a condition such as avascular necrosis, a labral tear or a stress fracture is suspected.
My X-ray looks bad but my pain is manageable. What does that mean?
X-ray appearance and symptoms often do not match. Some people have marked changes on imaging with modest pain, and others have significant pain with relatively mild changes. Treatment decisions are based on how much the hip is affecting your daily life rather than on the severity of the X-ray alone.
Does hip arthritis always get worse?
Hip osteoarthritis generally progresses over time, but the rate varies considerably and is difficult to predict. Some people remain stable for years with modest symptoms; others deteriorate more quickly. Symptoms also fluctuate, with painful periods followed by quieter phases, so decisions are based on the overall trend rather than a single bad month.
What is femoroacetabular impingement?
Femoroacetabular impingement is a condition in which the ball and socket are shaped so that they catch against one another during movement. It typically causes groin pain in younger, active adults, particularly on deep bending or rotation, and over years it can damage the cartilage and lead to osteoarthritis.
What is hip dysplasia?
Hip dysplasia describes a hip socket that is shallower than normal, so the load passing through the joint is concentrated over a smaller area of cartilage. It is often present from childhood but may not cause symptoms until early adulthood, and it is a recognised cause of osteoarthritis developing at a younger age than usual.
What is avascular necrosis of the hip?
Avascular necrosis occurs when the blood supply to the head of the femur is interrupted and part of the bone dies and can collapse. Causes include high-dose corticosteroid use, heavy alcohol intake, previous fracture and some medical conditions, though sometimes no cause is identified. It is diagnosed on MRI when X-rays appear normal.
References.
- Australian Orthopaedic Association National Joint Replacement Registry. Annual Report. Adelaide: AOA.
- Royal Australian College of General Practitioners. Guideline for the management of knee and hip osteoarthritis. 2nd edn. East Melbourne: RACGP.
- Katz JN, Arant KR, Loeser RF. Diagnosis and treatment of hip and knee osteoarthritis: a review. JAMA. 2021;325(6):568-578.
This page provides general information about a medical condition and a surgical procedure. It is not individual medical advice and does not replace consultation with a qualified practitioner. Outcomes vary between individuals and all surgery carries risk. A referral is needed for a consultation with Professor Daevyd Rodda; without one, you can start with the practice nurse practitioner, who can provide it.