Why hip OA is more than a wear-and-tear inconvenience

Around 240 million people worldwide live with activity-limiting osteoarthritis, and the hip is one of the joints most commonly and most severely affected. Globally, OA ranks among the leading causes of disability in adults — a scale that sits uncomfortably alongside the widespread assumption that hip pain is simply something to push through.

The condition is progressive. Cartilage loss does not plateau and wait; it advances, narrowing the joint space, remodelling bone, and steadily eroding the movements that underpin ordinary life — walking to the end of the road, climbing stairs, turning over in bed without waking. Stiffness that begins as a morning inconvenience can, over months or years, become the dominant fact of a person's day.

What makes hip OA genuinely serious is not only what it does to the joint. Research published in JAMA in 2021 found that people with OA are substantially more sedentary than those without, and carry approximately a 20% higher age-adjusted mortality as a result. The hip condition drives inactivity; the inactivity carries a systemic cost that extends well beyond discomfort.

Understanding where a patient sits on the spectrum of severity — and what that means for their options — is therefore not a matter of curiosity. It is the necessary first step toward deciding what to do next.

How doctors grade hip OA severity

The two tools clinicians most commonly use when assessing hip OA are an X-ray grading system and a patient questionnaire — and together they provide a fuller picture than either offers alone.

The Kellgren-Lawrence scale

The Kellgren-Lawrence (KL) scale rates structural damage on plain X-ray across five grades:

• Grade 0 — normal joint
• Grade 1 — doubtful joint space narrowing; possible small osteophytes (bone spurs)
• Grade 2 — definite osteophytes; possible narrowing of the joint space
• Grade 3 — moderate narrowing, multiple osteophytes, early sclerosis (bone hardening), and possible bony deformity
• Grade 4 — gross joint space loss, large osteophytes, severe sclerosis, and definite deformity

Grades 1–2 typically correspond to aching in the groin or front of the hip — particularly when bending or rising from a chair — with morning stiffness that clears within about 30 minutes. By Grades 3–4, pain tends to become persistent, often radiating to the thigh or knee, and routinely disrupts sleep. Many patients at this stage develop an antalgic gait — an unconscious limp that offloads the painful side — and find that tasks such as putting on shoes or climbing stairs require considerable effort.

An alternative system, the Tönnis classification, is used in some UK orthopaedic settings and covers broadly the same ground; the two approaches complement rather than contradict each other.

WOMAC

Where the KL scale measures structural damage, the WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) measures lived experience. Developed in 1982 and self-administered, it captures pain, stiffness, and physical function — dimensions that X-rays cannot show. A patient who scores heavily on function may have a very different clinical picture from someone with the same X-ray grade who remains largely active.

Both tools inform the treatment conversation rather than settle it. Clinician judgement, patient goals, and response to conservative management all carry weight alongside the numbers.

When X-ray severity and symptoms don't line up

Two patients can sit in the same consulting room with identical X-ray reports — Grade 3 changes, moderate joint space narrowing, multiple osteophytes — and have profoundly different lives because of them. One has adjusted her routine, manages with exercise and occasional anti-inflammatories, and still walks the dog each morning. The other cannot sleep through the night, cannot put on his shoes without assistance, and has stopped going out because the pain from the short walk to the car is too unpredictable.

Same film. Opposite functional realities.

This divergence is well recognised clinically: radiographic severity and symptom burden do not follow a tidy, predictable relationship. Some patients carry significant structural change on X-ray with relatively modest day-to-day symptoms; others reach real functional collapse at earlier structural grades. Current guidelines, including the 2025 clinical practice update from the Journal of Orthopaedic and Sports Physical Therapy, reflect this by anchoring treatment decisions in symptom burden and functional loss rather than X-ray grade alone.

Understanding this matters because it shifts the right question. Presenting a film and asking for a verdict is not how sound clinical decisions are made. The question that actually drives the pathway forward is what the hip is preventing — and answering that requires a thorough clinical assessment, not just an image.

The conservative treatment phase and its realistic limits

Structured conservative care is the appropriate starting point regardless of X-ray grade, and for many patients it provides meaningful symptom control for years.

The cornerstones are well established: a supervised, progressive exercise programme — land-based or hydrotherapy for those whose joints tolerate impact poorly — combined with weight management where relevant, and patient education about the condition's natural course. Topical or oral NSAIDs reduce pain and inflammation, and short-term corticosteroid injections can ease flare-related swelling enough to restore participation in rehabilitation. Their benefit typically fades within weeks to months, however. An injection can be a useful bridge to better function; it does not address the underlying structural problem.

For selected patients — typically those with Grade 2–3 changes who retain reasonable joint space and have not yet exhausted multiple treatment cycles — biological options such as micro-fragmented fat injections may help improve comfort or buy additional time before surgical assessment. The evidence base in hip OA is less established than in the knee, and the more likely responders are those with moderate rather than end-stage disease, which is why a specialist assessment is needed before proceeding.

Conservative care works best when the joint still has enough structural integrity to respond to it. The honest limit appears when pain is disrupting sleep, when basic self-care has become genuinely difficult, and when repeated treatment cycles have failed to restore meaningful function. At that point, continued non-surgical management is no longer a strategy — it has become a delay, and that pattern of functional collapse despite appropriate care is itself a clinical signal worth taking seriously.

Signs that a replacement assessment is worth considering

Several specific thresholds — drawn from NHS guidance and international clinical guidelines — help clarify when the conversation about surgical assessment becomes reasonable.

• Sleep disruption most nights. Occasional bad nights are common with hip OA. When pain is waking a patient regularly, or preventing sleep altogether, that consistency is a recognised clinical signal — not just a quality-of-life complaint.
• Loss of basic daily function. Difficulty dressing the lower body, rising from a low chair, or managing stairs without significant effort represent meaningful functional decline. Inability to put on socks and shoes unaided is a commonly cited practical marker.
• A persistent limp. When an antalgic gait — shifting weight to offload the hip — becomes a habitual pattern rather than an occasional response to a harder day, the body has begun compensating structurally.
• Failure of a sustained conservative programme. A structured, supervised effort over roughly three to six months, combined with imaging showing advanced joint damage, is typically the point at which continued non-surgical management stops offering a realistic return.

The convergence of these factors — not any single item in isolation — is what ordinarily moves a clinician toward recommending specialist review. Seeking that assessment is an information-gathering step. It opens a conversation about options; it does not commit anyone to an operating list.

What specialist assessment and surgical planning actually involve

A good surgical assessment does more than review an X-ray. It brings together clinical examination — including whether internal rotation reproduces the patient's characteristic groin pain — alongside functional scoring such as the WOMAC index, which maps pain, stiffness, and daily activity limitations into a measurable picture. Together, imaging and patient-reported function allow a surgeon to understand not only the structural state of the hip but how much it is actually limiting someone's life.

Implant selection and surgical approach are also part of pre-operative planning — and they matter. Not all hip replacements are performed the same way. The conventional posterolateral approach involves dividing the short external rotator tendons at the back of the joint; those tendons require approximately 90 days to fully heal, creating a window of heightened dislocation risk. One approach designed to address this is the SPAIRE technique — Saves Piriformis And Obturator Internus with Repair of Obturator Externus — which preserves those posterior tendons rather than cutting them. The aim is to reduce disruption to the tissues responsible for joint stability, which may support earlier confident mobilisation for selected patients within this pathway.

Professor Paul Lee, Consultant Orthopaedic Surgeon at the Royal London Hospital and in private practice at 108 Harley Street, developed the SPAIRE technique. His practice spans hip preservation and hip replacement decision-making — meaning assessment weighs whether surgery is warranted at all before planning how to perform it. That preservation-first perspective is the context in which SPAIRE sits: an approach designed around stability, not simply turnaround time.

Modern implants, in well-selected cases with thorough pre-operative planning, carry survivorship data extending beyond 30 years — a figure that carries weight only when the decision to operate has been made for the right reasons, grounded in the kind of clinical and functional evidence this section describes.

1. [1] Hip replacement - NHS. https://www.nhs.uk/conditions/hip-replacement/ https://www.nhs.uk/conditions/hip-replacement/