What hip OA is and why it progresses the way it does

The phrase 'wear and tear' is widely used to describe hip osteoarthritis, but it understates what is actually happening. Hip OA is a biological disease affecting the cartilage that lines the ball-and-socket joint formed by the femoral head (the ball) and the acetabulum (the socket); as that cartilage degrades, the underlying bone, joint lining, and surrounding soft tissues are progressively drawn into a cycle of damage and repair that reshapes the joint over years.

Several factors raise the risk: increasing age, obesity, female sex, a family history of OA, and significant previous hip injury. Femoroacetabular impingement (FAI) — an anatomical mismatch between the ball and socket — is thought to be implicated in up to 50% of hip OA cases as an early structural trigger.

One reason hip OA can advance quietly is that cartilage itself has no nerve supply. Early loss of cartilage causes no direct pain signal; discomfort arises later, when underlying bone, the joint lining (synovium), and surrounding soft tissues become involved. This also means symptoms that feel like hip OA may sometimes originate from the lower spine or groin, and careful clinical assessment is needed to distinguish them.

Importantly, the disease does not follow a single, relentless trajectory. Evidence from long-term cohort studies suggests many people reach a period of symptom stability even as imaging changes continue — a point that shapes how the replacement conversation should be timed.

The sections that follow trace what each stage of hip OA looks and feels like, and at what point surgery enters the picture.

The four stages of hip OA and what each one feels like

Most people living with hip osteoarthritis find it useful to know where they sit on the disease arc — not because the stages predict what will happen next, but because each one has a recognisably different texture of daily experience.

Stage 1 — Structural change before symptoms

At Stage 1, tiny bone spurs (osteophytes) begin forming at the joint margin, but cartilage remains largely intact and X-rays often appear near-normal. Most people at this stage notice nothing at all; the changes are detectable on MRI before any pain registers. Occasional tightness in the groin after sustained activity may be the only hint.

Stage 2 — The first visit to a GP

Stage 2 is when hip OA most commonly comes to medical attention. Bone spurs are now clearly visible on X-ray and early cartilage degradation has begun. Patients typically describe morning stiffness that eases within 20–30 minutes, and an aching discomfort after longer walks or a day on their feet. The hip joint itself is still far from severely compromised, which means there is meaningful room for non-surgical management — physiotherapy, weight management, and activity modification — to reduce symptoms and preserve function.

Stage 3 — Activity starts to shrink

By Stage 3, significant cartilage has been lost and the joint space is visibly narrowed. Pain during everyday activity — walking any distance, climbing stairs, getting in and out of a car — becomes persistent rather than occasional. Sleep is sometimes disturbed. Patients frequently do not register how much hip range of motion they have already lost; the restriction creeps in so gradually that altered movement patterns compensate for it unnoticed.

Crepitus — a clicking or grinding sensation — may be present at any stage from Stage 2 onwards and does not by itself indicate urgency or rapid deterioration.

Stage 4 — Bone-on-bone contact

At Stage 4, cartilage has been worn through in the affected area, leaving bone surfaces in direct contact. Pain is present at rest and wakes people at night; basic tasks such as putting on shoes and socks, driving, and managing stairs become genuinely difficult. This is the stage at which total hip replacement typically enters the conversation — not because the stage label demands it, but because conservative treatments have usually reached their limit.

Does hip OA always get worse?

Over a decade of follow-up in the CHECK cohort — 588 people presenting with early symptomatic hip pain in primary care — radiographic OA prevalence nearly tripled, from 19% to 49%. Yet only 12% (roughly 1 in 9) underwent hip replacement in that period. Those who did not go on to surgery maintained broadly stable pain scores and physical function, with pain medication use rising only modestly from 43% to 50%.

X-ray grade is one input, not a verdict. Pain, sleep quality, and the effect on daily tasks carry equal weight when a consultant is considering the pathway ahead — which is why two people with the same X-ray appearance can have very different clinical trajectories.

Part of that divergence may come from biology that plain X-rays do not capture. A 2014 MRI follow-up study of 19 participants with hip joint pain found that bone-level signal changes tracked closely with pain activity — appearing during painful episodes and largely resolving when pain eased. When pain persisted, those bone alterations were associated with rapid radiographic progression to a more advanced stage. The implication is that OA involves bone-level processes as much as cartilage loss, which helps explain why symptoms can fluctuate in ways a plain X-ray does not predict.

The CHECK cohort was drawn from Dutch primary care; comparable UK-specific long-term progression rates are not directly available from this data. That said, the pattern — a stable-symptom majority alongside a smaller surgical minority — is consistent with clinical experience in hip OA more broadly.

For the minority who do progress to severe, bone-on-bone disease, the picture changes considerably — and that is where the sections that follow are directed.

Managing hip OA before surgery

Reaching Stage 3 or 4 does not make surgery automatic. For the majority of patients, the pathway begins — and for many, it ends — with structured non-surgical care.

Exercise first. Land-based exercise, typically guided by a physiotherapist, is first-line treatment at every stage of hip OA. Targeted hip-strengthening programmes help the muscles surrounding the hip joint compensate for cartilage loss, reducing load on the joint surface and improving stability. The pain reduction that comes from a structured programme is not dependent on reversing structural damage; it works through neuromuscular conditioning and improved joint mechanics. Water-based exercise offers a lower-impact alternative for patients whose pain currently limits land-based activity.

Weight management. Every additional kilogram of body weight increases the mechanical load on the hip joint. Reducing that load slows symptom progression and makes exercise more tolerable — two compounding benefits.

Injection options. Cortisone injections can reduce joint inflammation and open a window of relief during which physiotherapy becomes more effective. Hyaluronic acid injections aim to supplement the joint's natural lubrication. Platelet-rich plasma (PRP) and micro-fragmented adipose tissue (mFAT) are used in some patients as biological support for joint tissue health. All four are symptom-management tools that can extend the conservative window; none reverses structural OA.

When conservative treatment has genuinely failed. The clinical threshold is ongoing significant pain despite at least three months of structured exercise, patient education, and appropriate analgesia — not a single physiotherapy course or a few weeks of trying. Sleep disruption, inability to manage basic daily tasks such as walking or dressing, and declining quality of life despite consistent adherence are the markers that move the conversation toward surgical assessment.

When hip replacement becomes the right conversation

No single X-ray finding triggers the replacement conversation. What moves a patient from conservative care to surgical assessment is an intersection of factors: persistent pain that disrupts sleep or requires daily analgesia, an inability to manage core tasks — walking, driving, putting on shoes and socks — and a meaningful decline in quality of life, all after a structured trial of exercise, education, and appropriate pain relief has run its course.

The NHS is explicit on this. The threshold is not a number on a Kellgren-Lawrence scale; it is the point at which the hip joint is materially impairing daily life and non-surgical treatment has been given a fair run.

Why timing matters beyond the threshold

Once the criteria are met, there is a practical reason not to wait. NHS elective hip replacement lists run at approximately 27 weeks — meaning that initiating specialist referral promptly, rather than persisting with management that has already failed, protects the patient from months of avoidable pain whilst waiting.

There is also a clinical argument against allowing disease to advance unchecked into end-stage. Operating on a hip with severely distorted anatomy and extensive scar tissue is a different undertaking: theatre time is longer, surgical risk is higher, and recovery is measured in years rather than months. Functional outcomes, even after a technically successful procedure, may remain permanently below what earlier intervention might have achieved.

High-quality trial evidence now supports the case for acting at the right moment. The 2024 PROHIP multicentre RCT compared total hip replacement with resistance training in patients aged 50 and over with severe hip OA and a surgical indication. At six months, the Oxford Hip Score improved by 15.9 points in the replacement group versus 4.5 points in those who continued with exercise alone — a clinically important difference. For patients who have crossed the threshold, exercise remains valuable, but it is not a substitute for surgery.

The honest answer on timing is this: the conversation becomes appropriate when NHS criteria are met and the hip is materially limiting life — not a stage earlier, and not unnecessarily later.

What modern hip replacement looks like and how to take the next step

Total hip replacement — replacing both the femoral head and the acetabular socket with a prosthetic implant — is among the most performed elective orthopaedic operations. Implant longevity has improved substantially; approximately 58% of total hip replacements are estimated to last 25 years, making timing a clinical decision rather than a reason to delay indefinitely.

Surgical technique has also evolved. The SPAIRE approach (muscle-sparing posterior) is designed to preserve the key muscles and tendons around the hip joint; the anterior Bikini approach uses an incision placed along natural skin lines and avoids cutting through posterior structures. Both are intended to reduce soft-tissue disruption and support earlier rehabilitation. Technique selection depends on individual anatomy and surgeon expertise — these approaches are described as minimising tissue damage rather than as having demonstrated superiority over standard methods in head-to-head trials.

Recovery is active from the outset. Rehabilitation typically begins within hours of surgery and advances on clinical criteria — strength, movement, and confidence — rather than by the calendar.

Lincolnshire Hip is part of the MSK Doctors group and accepts patients without a GP referral, with access points in Sleaford and Grantham for patients across Lincolnshire and the wider non-London UK catchment. An early specialist consultation can map the pathway whether surgery is a near-term prospect or still some way off — because the decision to replace a hip is clinical, not administrative, and having clear information at the right moment is what makes the difference.

1. [1] Pathophysiology and Progression of Hip Osteoarthritis: Bone Alterations Follow-up Study. (2014). https://doi.org/10.2174/1874312901408010046 https://doi.org/10.2174/1874312901408010046
2. [2] Hip replacement — NHS. https://www.nhs.uk/conditions/hip-replacement/ https://www.nhs.uk/conditions/hip-replacement/