Why focal hip cartilage damage needs more than rest

A common question after receiving this diagnosis is whether rest and physiotherapy alone might settle things down. For a focal osteochondral defect of the femoral head, the honest answer is no — and understanding why matters before weighing up the surgical options.

An osteochondral defect is not simply a scratch on the cartilage surface. It involves a full-thickness loss of hyaline cartilage together with damage to the layer of bone immediately beneath it. Hyaline cartilage has virtually no capacity to regenerate itself: it contains no blood vessels, no lymphatics, and too few repair cells to fill a structural gap. When a defect forms on the femoral head, the body may partially fill it with fibrocartilage — a softer, mechanically inferior tissue — but this substitute breaks down under load and does not restore the smooth, durable surface the hip needs.

The hip's anatomy makes the situation more pressing than an equivalent defect in some other joints. Because the femoral head is a ball sitting inside a deep socket, it bears the full weight of the body on every step, stair, and turn. There is no position of genuine unloading in daily life. A focal defect sits directly in this load path, and each loading cycle erodes the edges further.

Defects of this kind arise from several different starting points: osteonecrosis of the femoral head, a direct impact injury, femoroacetabular impingement (FAI) damaging the articular surface over time, slipped capital femoral epiphysis (SCFE), or the childhood condition Legg-Calvé-Perthes disease. The underlying cause matters for planning treatment, but the risk they share is the same — without active intervention, focal lesions on the femoral head progress reliably to symptomatic hip osteoarthritis.

For younger, active patients in whom joint replacement is not yet appropriate, cartilage preservation surgery aims to restore the articular surface before that joint-wide deterioration sets in. Osteochondral autograft transfer — OATS or mosaicplasty — is one such option, and the sections that follow explain how it works and what the evidence shows.

How plug transfer surgery works on the hip

Plug transfer surgery — whether OATS or mosaicplasty — follows the same core logic: borrow healthy bone and cartilage from a part of the femoral head that bears little load, and use it to repair the damaged area that bears a great deal.

The surgeon first drills one or more cylindrical tunnels precisely into the defect site, removing the damaged tissue. Matching plugs of hyaline cartilage with the subchondral bone still attached are then harvested from a low-load donor zone on the same femoral head — a turf-repair analogy is apt, transplanting a healthy core into a worn patch. Each plug is press-fit snugly into its tunnel, restoring a continuous articular surface made of the patient's own native hyaline cartilage rather than the fibrocartilage that bone marrow stimulation techniques produce.

The two terms reflect the size and number of plugs used. OATS typically transfers one or two larger plugs to fill a smaller, well-defined lesion. Mosaicplasty uses multiple smaller plugs arranged in a tessellated pattern to cover a larger or more irregular defect — the same principle, scaled up. In clinical practice, the surgeon's choice between them follows the geometry of the lesion rather than representing a fundamentally different operation.

Surgical access is where the hip presents its greatest challenge. The deep ball-and-socket geometry means the femoral head cannot be reached without either dislocating the joint or working around it. Classical technique requires a formal surgical hip dislocation, which carries a small risk of disrupting blood supply and causing avascular necrosis of the femoral head. Newer approaches — including a direct anterior approach described by Coulomb in 2021 and an arthroscopic-assisted retrograde technique developed to avoid full dislocation — have been introduced specifically to reduce this risk, broadening the range of patients and surgeons for whom the procedure is practical.

The main procedure-specific risks beyond the access question are donor-site morbidity at the harvest zone and the possibility of incomplete plug integration.

Who is a realistic candidate for this procedure

Deciding whether this procedure is appropriate starts with three practical questions: how old is the patient, how large and localised is the defect, and is the rest of the hip joint still fundamentally intact?

The typical candidate is under 50, physically active, and has a focal osteochondral lesion rather than the diffuse, whole-joint cartilage loss of established hip osteoarthritis. Published clinical series report mean patient ages of 24–29 years — a group for whom hip replacement is not a realistic near-term answer and for whom few other surgical options exist. That said, age is a guide rather than a strict cut-off; overall joint health and activity level carry equal weight.

Defect size is a meaningful planning consideration. OATS is generally well-suited to lesions of roughly 1–2 cm²; mosaicplasty, with its multi-plug approach, can address up to approximately 4 cm². Lesions larger than this may require a different technique altogether — fresh osteochondral allograft (OCA), which uses donor rather than the patient's own tissue. MRI or direct arthroscopic assessment is needed to map lesion dimensions accurately; plain X-ray alone is insufficient to characterise cartilage loss.

The underlying cause — osteonecrosis, trauma, FAI sequelae, SCFE, or Perthes disease — influences surgical planning but does not by itself determine suitability. What does exclude a patient is advanced or diffuse hip joint arthritis: cartilage preservation surgery depends on there being a joint worth preserving. For those patients, the appropriate conversation is about hip replacement rather than repair.

What the evidence actually shows for the hip

Two published cohort studies provide most of what is known about hip-specific outcomes, and both are worth examining plainly.

The longest follow-up comes from a Bone & Joint Open 2023 series tracking 11 hips in patients with a mean age of 28.6 years over an average of 18.5 years — the most extended published data of its kind for femoral head osteochondral autograft transfer. Cumulative native hip survivorship was 91% at five years and 62% at ten years; six patients ultimately required conversion to total hip arthroplasty at a mean of 10.3 years post-surgery. The authors frame the procedure explicitly as a 'time-saving bridge' — it bought more than a decade of native hip function for the majority of patients in a group who, at the time of surgery, had virtually no other viable surgical option.

A smaller series by Johnson (2017, n = 5, mean age 24.8 years) reported Harris Hip Scores rising from 60.8 pre-operatively to 86.6 at approximately 54 months — broadly, a move from moderate disability toward near-normal function. Four of the five patients reported complete resolution of pain and a return to their baseline activities; none showed radiographic evidence of defect progression, and no operative complications were recorded.

The honest limitations of this evidence base are worth stating directly. The largest series involves only 11 hips. No randomised controlled trials exist. The patient populations across studies are heterogeneous in aetiology. Long-term survivorship falls substantially beyond ten years — dropping to around 37% at 20 years in the 2023 cohort — and outcome data for lesions larger than 2 cm² remain sparse. These gaps do not invalidate the procedure's role for the right patient, but they do mean that expectations should be grounded in what the evidence actually demonstrates: meaningful preservation of native hip function over the medium term, with declining durability over the longer term.

Recovery and returning to activity after hip plug transfer

Weeks 0–8: protecting the repair

For the first six to eight weeks, strict non-weight-bearing or toe-touch weight-bearing on crutches is the central requirement — press-fitted plugs need time to osseointegrate into the surrounding bone, and early loading risks displacement. Active patients often find this the most demanding phase psychologically; planning ahead (work schedules, transport, home layout) makes a material difference to how manageable it feels.

Physiotherapy begins within this window, focusing on gentle hip range of motion and limiting muscle wasting rather than building strength.

Months 2–4: progressive loading

As crutches are weaned, rehabilitation shifts to hip muscle strengthening and gait re-education. Two sites are healing concurrently — the repair zone and the donor harvest area — so discomfort may arise from either location. Recognising this helps patients distinguish expected recovery soreness from something warranting clinical review.

Months 4–6: return to activity

Light sport and lower-impact activities become possible for most patients around this point, though these figures are estimates rather than fixed targets. Symptom response and clinical review should guide the actual timing; individual variation is normal.

12 months: full maturation

Cartilage maturation continues for up to a year post-surgery. Physiotherapy across this entire period is integral to the outcome — not an optional extra. Consistent rehabilitation engagement carries as much weight as the surgery itself.

Getting assessed for hip cartilage preservation in Lincolnshire

Deciding whether plug transfer surgery is the right option cannot be settled from an article alone — the answer depends on defect size confirmed on MRI, the underlying cause, the condition of the surrounding joint, and individual factors that only a clinical assessment can establish. A specialist consultation will typically cover clinical history and examination, MRI review (weight-bearing imaging where the clinical picture warrants it), and a frank discussion of where the patient sits on the hip preservation pathway: cartilage restoration surgery, injection support, or a more conservative approach at this stage.

Not every focal hip defect will prove suitable for OATS or mosaicplasty. Some will be better served by biologic injection support; others may not yet need intervention beyond structured physiotherapy. The assessment appointment exists precisely to answer that question for the individual rather than in the abstract.

For patients across Lincolnshire and the wider non-London catchment, specialist hip assessment is available locally without the need to travel to London, with clinics in Sleaford and Grantham. Lincolnshire Hip is part of the MSK Doctors group and accepts patients without referral for hip assessment.