What the diagnosis actually means for your hip

An MRI report showing femoroacetabular impingement (FAI) with cartilage damage can feel alarming. In practice, it is better understood as a map of mechanical risk — information that shapes what comes next, not a verdict about surgery or decline.

FAI is a shape mismatch: the femoral head, the acetabular rim, or both have a geometry that generates abnormal contact pressure during hip flexion and rotation. It is a structural variation, not a disease. The cartilage damage — termed a chondral lesion — is what that repeated abnormal contact produces over time, ranging from surface softening at the mildest end to partial- or full-thickness cartilage loss at the most severe.

Two points are worth holding clearly. First, imaging findings and pain levels do not reliably mirror each other: some people have marked MRI changes with relatively mild symptoms, while others have modest findings and significant functional limitation — both are clinically valid presentations and both inform the assessment. Second, the MRI report is one piece of a larger picture; defect size, lesion grade, the pattern of impingement, and how symptoms affect daily life together determine the realistic options.

What makes early recognition worthwhile is momentum: without addressing the underlying bone-shape conflict, the hip continues to load already-damaged cartilage with each movement, and mechanical attrition may progress toward osteoarthritis over time.

How cam and pincer FAI injure cartilage

The type of bone-shape abnormality determines where cartilage damage appears — which is why the location of a lesion on MRI is rarely random.

In cam-type FAI, a bony prominence on the edge of the femoral head creates a non-spherical profile. During hip flexion — bending to sit, squat, or climb stairs — this bump grinds against the cartilage lining the anterosuperior acetabulum, the front and upper inner surface of the socket. The repeated contact generates shear forces the cartilage was not designed to withstand, stripping and softening the tissue in a characteristic arc.

Pincer-type FAI works differently. Here, the acetabular rim extends too far over the femoral head, pinching the labrum at the front of the socket with each movement. The direct damage falls on the labrum, but secondary — or contrecoup — cartilage injury frequently appears at the posterior acetabulum, where the femoral head levers against the opposite wall under load. Combined morphology, where cam and pincer features coexist, is the most common presentation; both damage patterns may therefore be present simultaneously.

The labrum is almost always involved. Its role is to form a fluid seal around the joint, distributing load evenly across the cartilage surface. Once a labral tear develops, that sealing function is compromised and mechanical stress concentrates on already-vulnerable cartilage — accelerating the very attrition the labrum was protecting against.

Because articular cartilage has no blood supply of its own, it cannot meaningfully self-repair once damaged. This biological limit is why the location and depth of a lesion on MRI carry real clinical weight: they reflect how far the mechanical process has already run, and they are one of the key inputs into decisions about the timing and nature of any intervention.

What hip MRI and MR arthrography can and cannot show

Standard hip MRI is a reliable guide to bone shape and moderate-to-severe structural damage — but what it reliably detects is not the same as what it can reliably exclude.

The scan will typically confirm whether cam or pincer morphology is present, identify labral tears, and show overt cartilage thinning or delamination where loss is significant. For partial-thickness chondral lesions — damage that has not yet reached full depth — sensitivity is lower, which means a broadly reassuring MRI does not rule out early-grade cartilage injury. This is one of the most clinically important limits to hold in mind when reading a report.

MR arthrography (MRA) reduces that gap. By injecting a small amount of gadolinium contrast directly into the hip joint before scanning, MRA improves the visibility of the labrum and partial-thickness cartilage delamination that standard sequences can miss. It is often requested when a labral or chondral lesion is clinically suspected but not clearly demonstrated on standard MRI.

For structured assessment, some centres use SHOMRI (Scoring Hip Osteoarthritis with MRI), a validated whole-joint scoring framework that applies a reproducible grading system to cartilage, bone marrow changes, and other features — bringing systematic evaluation to the hip analogous to established knee scoring tools.

At specialist centres, compositional sequences add a further layer. dGEMRIC measures glycosaminoglycan concentration in the cartilage matrix; T2 mapping and T1rho sequences assess collagen and proteoglycan integrity respectively — detecting biochemical depletion before any structural defect is visible on standard imaging. Research in hip dysplasia has used dGEMRIC to identify pre-symptomatic cartilage changes and to predict early failure of joint-preserving surgery. These sequences are not part of routine NHS scanning, but some private orthopaedic centres offer dGEMRIC as part of a pre-operative workup when early cartilage status is a key decision variable.

Cartilage grades 1 to 4: what the numbers mean

When a surgeon or radiologist refers to a cartilage "grade", they are using a four-point classification that describes how far through the cartilage thickness an injury extends.

Grade 1 marks the earliest structural change: the surface may show softening or fibrillation, but the cartilage layer remains intact. Many Grade 1 lesions are manageable with conservative care and do not, on their own, point toward surgery.

Grade 2 extends the damage to less than half the cartilage depth — partial-thickness loss that is clinically significant but has not yet reached the deeper layers.

Grade 3 crosses the halfway point, with injury exceeding 50% of cartilage depth. This grade is further sub-classified A through D depending on how close the lesion comes to the calcified cartilage layer and the tidemark beneath it. That sub-classification is a clinician-level detail patients need not memorise; knowing Grade 3 represents a spectrum is sufficient for an informed discussion with a specialist.

Grade 4 denotes full-thickness loss reaching subchondral bone. At this depth, treatment options narrow considerably and the conversation about joint preservation versus longer-term joint health becomes more urgent.

Grade alone, however, does not tell the complete story. Defect area — measured in cm² — is the second critical dimension: a small Grade 3 lesion and a large Grade 3 lesion carry materially different treatment implications, influencing whether microfracture, osteochondral grafting, or a cell-based approach is most appropriate.

One practical distinction is worth holding clearly: MRI grading and arthroscopic grading do not always agree. Direct visual inspection of the joint at arthroscopy remains the reference standard for definitive cartilage grading, particularly for partial-thickness lesions where MRI sensitivity is limited. This is not a shortcoming to be concerned about — it is the reason that specialist review of the original images, rather than the written report summary alone, plays an important part in surgical planning conversations.

Treatment options matched to your cartilage grade

The right approach depends on grade, defect area, and — critically — whether the underlying bone shape abnormality has been corrected.

Conservative care: the first stage across all grades

Structured physiotherapy targeting hip stability, load distribution, and range of movement is the appropriate starting point while the full clinical picture is being established. Anti-inflammatory management addresses symptoms in parallel. For Grade 1 lesions and contained early Grade 2 damage, this stage may be sufficient on its own; for higher grades, it remains the foundation for any intervention that follows.

Injectable biologic support for focal early-to-mid-grade lesions

For Grades 1 to 3 with a focal defect and preserved joint architecture, injectable treatment sits between conservative management and surgical repair.

ChondroFiller injection — an acellular collagen scaffold delivered under ultrasound guidance as an outpatient procedure — provides a matrix within the defect that supports recruitment of the patient's own progenitor cells to promote new tissue formation. No theatre admission is required.

Surgical cartilage repair

Microfracture creates small perforations in the subchondral bone to stimulate a fibrocartilage repair response. It is generally appropriate for smaller focal defects, typically under approximately 2 cm², with the caveat that fibrocartilage differs mechanically from the original hyaline tissue it replaces.

MACI (matrix-induced autologous chondrocyte implantation) uses the patient's own cultured chondrocytes embedded in a scaffold. The SUMMIT trial demonstrated significantly improved KOOS pain and function scores at two and five years for lesions of 3 cm² or greater, compared with microfracture. Both the size thresholds and the trial data are drawn from knee literature; hip-specific randomised evidence remains limited, so these figures are applied to acetabular repair by extrapolation rather than direct evidence.

Addressing the mechanical cause

Residual cam deformity that continues to load the acetabular surface will compromise any cartilage repair, regardless of technique. Correcting the bone morphology and managing the cartilage defect need to be considered together — an unaddressed impingement mechanism undermines the longevity of whatever repair is undertaken.

Getting a specialist assessment in London

Persisting hip pain — or an MRI confirming FAI with chondral changes — warrants specialist input if symptoms have not improved after six to eight weeks of structured conservative management, or sooner where pain is severe or significantly limiting daily function.

A specialist consultation goes beyond reviewing the written imaging report. The clinician will take a detailed history, assess movement and loading patterns on examination, and review the original MRI sequences directly. That combination is what allows an informed judgement of whether cartilage damage is the primary pain source, whether the FAI morphology has been adequately corrected, and which point on the treatment pathway is most appropriate for that individual.

For patients in London seeking this assessment, the ChondroFiller injectable collagen scaffold pathway is available at the London Cartilage Clinic on Harley Street. Professor Paul Y. F. Lee leads delivery of the treatment there; the clinic is the UK certified centre for ChondroFiller. Appointments can be booked at londoncartilage.com.

1. [1] Femoroacetabular impingement. https://en.wikipedia.org/?curid=20754811 https://en.wikipedia.org/?curid=20754811
2. [2] Hip arthroscopy. https://en.wikipedia.org/?curid=31963181 https://en.wikipedia.org/?curid=31963181
3. [3] Cartilage. https://en.wikipedia.org/?curid=166945 https://en.wikipedia.org/?curid=166945