Three variables that drive the decision

The practical question most patients bring to their first hip consultation is not 'which technique?' but something more immediate: is there still something worth preserving in this joint, or has it reached the point where replacement is the right answer?

Three clinical variables shape that answer: the size and character of the cartilage damage, the overall stage of osteoarthritis in the hip, and the patient's age. None of these works as a standalone trigger. A patient in their early thirties with widespread bone-on-bone wear is not a repair candidate despite their age; a patient in their mid-fifties with a small, focal defect from an old sports injury may well be. The variables interact, and it is their combination that guides the clinical decision.

Two secondary factors tighten or loosen that window further. Body mass index matters because higher loads accelerate cartilage wear and can undermine the biological conditions a repair needs to succeed. Activity level matters because both pathways — preservation and replacement — carry different demands on recovery and rehabilitation, and realistic expectations about return to activity inform which route is appropriate.

Mapping where any individual sits across all of these variables is the task of specialist assessment.

How defect size determines your repair options

Defect size is the most quantifiable input into the repair decision, and it maps — loosely — onto a hierarchy of techniques, each designed for a different scale of cartilage loss.

Small, focal defects of roughly under 2 cm² are typically addressed by marrow stimulation (microfracture) or osteochondral autograft transfer (OATS, sometimes called mosaicplasty). The distinction between them matters for durability: microfracture generates fibrocartilage, a lower-grade scar-like tissue rather than true hyaline cartilage, and clinical results from microfracture frequently decline after two to three years. The procedure can also disrupt the subchondral bone plate, which may limit what further options remain available. OATS, by contrast, transplants native hyaline cartilage plugs from a lower-demand area of the joint — a more durable biological foundation that becomes particularly relevant for younger or more active patients placing sustained load on the repair. Microfracture retains a historical role for small lesions in carefully selected cases but is no longer regarded as a modern first-line choice.

Mid-range defects of 2 to 8 cm² move into the domain of AMIC — autologous matrix-induced chondrogenesis — a single-stage approach that pairs marrow stimulation with a scaffold layer to encourage more structured tissue regeneration. In O'Connor et al.'s 2018 systematic review of 1,484 patients, AMIC recorded the highest success rate of the techniques analysed, at 99.7%.

Larger or deeper lesions may suit MACI, a two-stage cell-based procedure. Where diffuse joint disease accompanies the defect, size alone no longer determines the route; the conversation tends to shift toward replacement rather than repair.

For suitable focal hip defects, ChondroFiller injection offers an outpatient option: it is a CE-marked injectable collagen scaffold positioned under ultrasound guidance, providing a structural matrix for the body's own cells to populate. As with every technique above, defect size is one input among several — joint loading, patient biology, and overall arthritis stage all bear on whether any preservation approach is appropriate.

Arthritis stage: where the preservation window closes

Knowing how worn the hip joint is — not just where — forms the second axis of the decision. That is where osteoarthritis staging draws the clearest line in the pathway.

Radiologists and orthopaedic surgeons use the Kellgren-Lawrence (KL) scale to grade hip OA on plain X-ray. Grades 1 and 2 — covering early joint-space narrowing and modest osteophyte formation — typically sit within the preservation window. At KL grade 3, narrowing becomes marked; at grade 4, the femoral head and acetabulum are effectively touching. The practical X-ray threshold for hip replacement consideration is joint space narrowing of 2 mm or less — bone-on-bone contact — which corresponds to KL grades 3 and 4. At that point, too little cartilage surface remains to support a repair procedure.

NHS England guidance sets a consistent bar: replacement is generally offered only for severe OA pain that has persisted despite physiotherapy, pain medication, and injections.

Diffuse OA — where damage is spread across the entire joint surface rather than confined to a focal patch — rules out repair regardless of the KL number. A hip with generalised cartilage thinning throughout the socket is outside the preservation window, whatever grade appears on the report.

The clinically hardest group sits at the KL 2–3 border. No randomised controlled trial has directly compared cartilage repair against hip replacement in this population, and that evidence gap is precisely why specialist assessment — reviewing MRI alongside plain X-rays — matters: a grade alone cannot capture the full clinical picture.

Age, activity level, and the timing problem

Timing sits at the intersection of defect size and OA stage — and it pulls in two directions at once.

Under 40–50, the balance generally favours preservation. Active patients with focal disease, adequate bone stock, and only minor arthritic change are the group most likely to achieve durable benefit from repair. Once patients are past 50–60 and diffuse OA is advancing, replacement typically becomes the more realistic and reliable pathway.

The longevity data for hip implants frames one side of the problem. Approximately 58% of total hip replacements are estimated to last 25 years, and most remain functional for at least 15 years. For a 45-year-old, that arithmetic points toward revision surgery at some point — a procedure that carries meaningfully higher risk than a first replacement. Around 10% of hip replacements require revision within 15 years; in absolute terms that is a minority, but the younger the patient at first operation, the more consequential that figure becomes as a long-term planning consideration.

The opposite risk is equally real. Prolonged pain, progressive muscle loss, and compensatory loading of the contralateral hip all accumulate before surgery and can impair post-operative recovery once it does take place. The therapeutic window for a straightforward outcome does not stay open indefinitely.

BMI above 30–35 and low activity levels tend to narrow the repair window further; high-demand patients under 50 with a contained focal defect typically extract the most durable benefit from a preservation approach. No single metric settles the timing decision — defect size, OA stage, and patient profile need to be read together before a recommendation can be made.

Repair and replacement pathways at Lincolnshire Hip

Both pathways — preservation and replacement — sit under one specialist roof at Lincolnshire Hip, which means patients still working out which route fits their situation do not need to be triaged to separate centres before getting a clear answer.

Preservation options

ChondroFiller injection is the primary scaffold-based option for suitable focal hip cartilage defects. As an outpatient procedure delivered under ultrasound guidance, it requires no general anaesthetic and no overnight hospital stay — the treatment is completed in a single visit. The mechanism and size considerations were covered earlier in this article; the practical distinction here is the absence of theatre time or surgical admission. For mid-size lesions in the 2–8 cm² range, AMIC (autologous matrix-induced chondrogenesis) is a single-stage surgical option that augments marrow stimulation with a collagen matrix. OATS (osteochondral autograft transfer) suits smaller, focal, deeper defects where transplanting native hyaline cartilage plugs is appropriate.

PRP injection is available alongside these options as a supportive adjunct: it may help manage symptoms and support the joint's biological environment, but it is not a cartilage repair procedure and does not restore lost tissue in the way scaffold or graft techniques aim to.

It is worth noting that hip-specific long-term follow-up data (beyond five years) for AMIC remains limited in the published literature — a point worth raising during a consultation rather than resolving from current evidence alone.

Hip replacement pathway

Professor Paul Lee, whose published work includes peer-reviewed papers on total hip replacement technique and hip arthroplasty, leads the private replacement pathway. Surgery is performed at Weymouth Street Hospital; the all-inclusive package, priced at £17,800, covers pre-operative planning, the procedure itself, and unlimited post-operative physiotherapy delivered locally at clinics in Grantham and Sleaford. For Lincolnshire patients, that local rehabilitation access removes the need for repeated travel to London throughout recovery.

What a specialist assessment actually covers

The single most useful question to put to a hip specialist — 'is my cartilage damage contained in one area or has it spread across the joint?' — is also the one that cannot be answered without combining an MRI (which maps cartilage thickness and defect boundaries) with a weight-bearing X-ray (which measures joint space and assigns a Kellgren-Lawrence grade). A GP appointment, or a scan report without clinical interpretation, rarely settles it.

A full specialist assessment cross-references those imaging findings with age, BMI, and functional demand. Patients who recognise the signs that the preservation window may already be closing — bone-on-bone ache present at rest rather than only on loading, pain that no longer varies with activity, or visible joint-space narrowing on a recent X-ray — tend to present at a different stage from those with intermittent mechanical symptoms and no prior imaging. Both groups benefit from that same assessment, but the pathway it points to may differ significantly.

The free discovery call at Lincolnshire Hip is designed for patients still working out which route applies to them — not only for those already decided on replacement. No GP referral is required. Lincolnshire Hip is part of the MSK Doctors group and accepts patients without referral for hip assessment.