Symptoms that first raise suspicion

Joint pain that doesn't quite add up is often the first clue. In active adolescents and young adults — particularly those in high-impact sports such as football, gymnastics, or distance running — a focal osteochondral defect may begin as a dull, poorly localised ache around a joint that worsens during or after activity and settles with rest. It is easy to attribute this to muscle soreness or a minor sprain, especially when there is no single dramatic injury to point to. Onset can be gradual and insidious, building over weeks or months of repetitive load, or it may follow a discrete event — a heavy landing, a pivot, a fall — after which the pain simply never fully resolves.

Recurrent swelling is a telling feature that tends to separate this pattern from ordinary overuse pain. Fluid accumulates in the joint during or after activity, then subsides with rest, only to return the next time demand is placed on the joint. This cycle of exertion-related effusion is consistent across sites — knee, ankle, and beyond — and warrants proper investigation rather than continued conservative management in isolation.

As a lesion loses stability, the character of the symptoms changes. Catching, locking, popping, or a sudden giving-way sensation during movement suggests that a fragment has become partially or fully detached and is beginning to interfere mechanically with the joint. These episodes — sometimes described by patients as the joint 'jamming' or 'clicking out' — are not simply pain; they represent a shift in the lesion's behaviour that changes the urgency of assessment.

What the clinical examination adds

A specialist's hands can add important detail to the symptom picture, even when findings look relatively unremarkable. The most consistent sign is localised tenderness on palpation along the joint line: pressing directly over the affected condyle or talar dome typically reproduces the patient's pain in a way that generalised pressure does not. Range of motion — both passive and active — is assessed for restriction or discomfort at the extremes. In longstanding cases, wasting of the quadriceps may be visible simply on inspection of the thigh.

Posture and limb alignment offer an additional steer. Genu varum (bow-legged alignment) concentrates load through the medial compartment; genu valgum shifts it laterally. Either pattern can help predict which part of the joint a lesion is most likely to occupy, narrowing the focus before any imaging is requested.

Despite this, no single manoeuvre confirms an osteochondral defect. The Wilson test — knee flexion combined with internal rotation, classically associated with medial femoral condyle OCD — has limited sensitivity and is not reliable in isolation. Equally, a near-normal examination does not rule the condition out. The role of physical assessment is to sharpen clinical suspicion to the point where the right imaging can be chosen and directed accurately — not to deliver a verdict on its own.

Why imaging starts with X-ray but can't stop there

The imaging sequence follows a clear logic: start with what is quick and available, then move to what is definitive.

Weight-bearing plain radiographs are ordered first. They are effective at excluding loose bodies floating in the joint, bony fractures, and significant degenerative change that might alter the clinical plan — all of which are important to rule out early. The limitation is that X-rays image bone, not cartilage. Roughly 40% of cartilage defects produce no visible abnormality on plain film. A reassuring X-ray, therefore, is not the same as a clear joint; it simply narrows the differential and sets the baseline.

MRI is the required next step, and the one that does the real diagnostic work. It is the only non-invasive modality that can directly assess the articular cartilage surface, detect oedema and early change in the subchondral bone beneath it, identify cysts or sclerosis, and — critically — look for a high-signal fluid rim on T2-weighted sequences between a fragment and its bone bed. That rim is the key MRI marker of instability, and its presence materially changes how urgently and in which direction treatment needs to move.

When MRI findings remain ambiguous — fragment boundaries unclear, stability uncertain — CT arthrography provides a further layer of precision. Intra-articular contrast combined with cross-sectional CT imaging gives sharper definition of the subchondral bone architecture and cartilage surface than MRI alone. It is a conditional step, deployed to answer a specific outstanding question rather than as routine.

Each modality, in short, interrogates the joint differently. The sequence is clinical reasoning, not administrative process.

What the MRI report is actually looking for

Four features stand out in a standard MRI report for an osteochondral lesion, and reading them together is what shapes the next clinical decision.

Cartilage integrity. The radiologist maps how much of the cartilage thickness is involved — less than half, more than half, or all the way through to the subchondral bone plate — and measures the extent in three planes. This depth-and-area picture tells the clinician how much tissue is at stake and how far the breach has progressed.

Subchondral bone signals. Oedema in the bone immediately beneath the cartilage appears as a bright signal on fluid-sensitive sequences. On its own, it reflects a reactive process and may settle when load is reduced. Cyst formation and sclerosis carry a different significance: they point to more established structural change, suggesting the bone has been under abnormal stress for some time and may be less likely to recover without active management.

The T2 fluid rim. A bright line of fluid tracking between a fragment and the bone behind it is the single most important instability marker. In plain terms, fluid is seeping in behind the fragment — a sign it is losing, or has already lost, its attachment. An absent rim generally indicates a stable lesion with time on its side; a visible rim accelerates the decision-making timeline considerably.

Fragment size. The exact dimensions in cm² are documented because size directly determines which treatment approaches are technically feasible. The treatment implications of those measurements are explored in the section on management options.

Grading systems: ICRS, DiPaola, and Hepple

Three classification systems appear most commonly in referral letters and imaging reports, and each was designed for a distinct purpose.

ICRS (International Cartilage Repair Society), Grades 0–4 scores how deeply the damage penetrates the cartilage layer. Grade 0 is a normal surface; Grade 1 indicates softening with the surface still intact; Grades 2 and 3 reflect partial-thickness loss below or above the 50% depth mark respectively (Grade 3 carries four subgrades, A–D, depending on proximity to the calcified cartilage layer); Grade 4 means the defect passes through the subchondral bone plate entirely. This system is applied both on MRI and confirmed directly at arthroscopy.

DiPaola, Stages I–IV is an MRI-based system focused on fragment stability rather than depth alone. Stage I describes softened but intact cartilage; Stage II a non-displaced fragment held by a low-signal fibrous union; Stage III a partially displaced fragment with a visible T2 fluid rim; Stage IV a fully detached loose body. Stability — not just size — is what DiPaola is designed to capture.

Hepple, Stages 1–5 was developed specifically for lesions of the talus and is the system most likely to appear in an ankle MRI report. Its particular value lies in Stage 2, which is split into 2a (subchondral fracture with surrounding bone marrow oedema) and 2b (fracture without oedema) — a distinction that influences how urgently a lesion is managed. Stage 5 denotes subchondral cyst formation.

These systems are not interchangeable: each was built around a specific question and, in Hepple's case, a specific joint. More importantly, a grade or stage is one input into a clinical decision, not the decision itself. A 'Grade 3 ICRS' or 'DiPaola Stage III' in a letter does not automatically indicate surgery; the consultant weighs that finding alongside lesion size, skeletal maturity, symptoms, and the patient's activity demands before recommending a path forward.

What the diagnosis means for your treatment pathway

Pulling together the findings from clinical examination, imaging, and — where necessary — arthroscopy, the consultant faces two questions that come before any discussion of specific treatments.

Skeletal maturity is the first fork. In younger patients with open growth plates — juvenile OCD — there is meaningful potential for the lesion to remodel with load reduction and activity modification alone. Adult OCD, where the physes have closed, rarely resolves without some form of active intervention, and the management conversation typically moves more quickly toward treatment options.

Lesion size and stability are the second parameter. The area documented on MRI and the stability grade together determine which treatment approaches are technically appropriate. Smaller, stable lesions diagnosed early carry a considerably better prognosis than large, unstable, or displaced fragments. The fluid rim, subchondral cyst formation, and fragment dimensions identified on MRI are not simply descriptive; they are the parameters that open or close specific treatment pathways.

Where arthroscopy is performed, it adds one further dimension: the surgeon physically probes the lesion, confirms the ICRS grade under direct vision, and — if findings warrant — can proceed to treatment in the same setting without requiring a second procedure.

The practical upshot is that no single finding triggers a decision. Grade, size, stability, skeletal maturity, and the patient's functional demands are weighed together at a specialist appointment, at which point the clinician can say — with genuine precision — which part of the treatment spectrum applies, why, and in what order. The right question to bring to that appointment is not 'what is my grade?' but 'what does my grade mean alongside everything else?'

1. [1] Osteochondritis Dissecans – Wikipedia. https://en.wikipedia.org/?curid=3762029 https://en.wikipedia.org/?curid=3762029