Synovial Chondromatosis

For Medical Students

What It Shows

Synovial chondromatosis is the formation of cartilage nodules within the synovium, which may detach into the joint. 5.5.11 covers the synovium.

Radiographs show the bodies only once they calcify, so magnetic resonance imaging finds the ones a film cannot. 5.3.1 covers the AP view.

It matters because this inverts the usual relationship, in which the radiograph is the cheaper first answer and the scan adds detail. 5.1.3 covers choosing the correct investigation.

How It Is Acquired

Obtain radiographs, since calcified bodies are obvious and diagnostic on them. 5.3.1 covers the AP view.

Use magnetic resonance imaging where the radiograph is normal and the history suggests bodies. 5.5.1 covers the standard protocol.

Count and locate the bodies, the posterior compartment and the recesses included. 5.4.4 covers the posterior knee.

Assess the cartilage, since the bodies abrade it. 5.5.7 covers the cartilage.

Assess the bone for pressure erosion where bodies collect. 5.5.6 covers the bones.

What Normal Looks Like

No intra-articular bodies on radiographs or on a scan. 5.3.1 covers the AP view.

A thin synovial lining with no nodules. 5.5.11 covers the synovium.

Recesses free of collected material. 5.4.4 covers the posterior knee.

Intact cartilage surfaces. 5.5.7 covers the cartilage.

What Abnormal Looks Like

Multiple bodies of similar size within the joint and its recesses. 5.5.11 covers the synovium.

Calcified bodies on the radiograph, which is the classical appearance. 5.3.1 covers the AP view.

Uncalcified bodies visible only on a scan, following cartilage signal. 5.5.7 covers the cartilage.

Collections of bodies in the posterior compartment and the recesses. 5.4.4 covers the posterior knee.

Pressure erosion of bone where bodies sit against it. 5.5.6 covers the bones.

MRCS Level

How It Is Acquired

In a viva the expected answer notes that a normal radiograph does not exclude the diagnosis.

The expected points are the radiographs, the scan when they are normal, the count and location, the cartilage, and the bone.

Say that uncalcified bodies are radiographically invisible. 5.3.1 covers the AP view.

Say that the bodies follow cartilage signal rather than fluid. 5.5.7 covers the cartilage.

Say that the distribution decides whether excision can be complete. 5.4.4 covers the posterior knee.

What Abnormal Looks Like

The reasoning expected is that the synovium is making cartilage, so the bodies have cartilage's composition and therefore its signal, and they calcify only with time. 5.5.7 covers the cartilage.

Many bodies of similar size suggest synovial origin, where a few of differing size suggest fragments detached from a joint surface. 5.11.5 covers osteochondral lesions.

The recesses and the posterior compartment collect bodies through gravity and joint motion, which is why a complete map matters before an operation. 5.4.4 covers the posterior knee.

Malignant transformation is rare and real, which is why follow-up rather than discharge is the usual course. 5.13.7 covers bone tumours.

How Good It Is

Magnetic resonance imaging is the best available test for the bodies and the radiograph the quickest test for the calcified ones.

Its best contribution is the full count, the distribution and the state of the cartilage. 5.5.7 covers the cartilage.

It is limited because small uncalcified bodies are easy to miss, because bodies and fluid can be hard to separate, and because the distinction from detached fragments rests on pattern. 5.11.5 covers osteochondral lesions.

No figures appear for accuracy on this page, under decision 028, and no body counts or size thresholds appear either: those are published quantities from particular series and this environment cannot check them.

FRCS Level

How Good It Is

At decision level the imaging decides the approach and whether a synovectomy accompanies the removal. 5.5.11 covers the synovium.

A complete map including the posterior compartment is what prevents a second operation. 5.4.4 covers the posterior knee.

Established cartilage damage changes the conversation from removal to arthritis. 5.3.17 covers joint space narrowing.

Recurrence follows incomplete synovectomy rather than incomplete body removal, which the imaging should support. 5.20.7 covers reporting the post-operative knee.

A solitary large body with aggressive features raises the rare malignant course. 5.13.7 covers bone tumours.

Where It Misleads

The commonest error is excluding the diagnosis on a normal radiograph. 5.3.1 covers the AP view.

Uncalcified bodies are read as fluid. 5.5.7 covers the cartilage.

Detached osteochondral fragments are reported as chondromatosis. 5.11.5 covers osteochondral lesions.

Posterior bodies are missed and return as a retained finding rather than a new one. 5.4.4 covers the posterior knee.

A body in a recess is read as a meniscal fragment. 5.6.6 covers bucket handle tears.

Fellowship Level

Where It Misleads

At fellowship level the knee has usually had bodies removed and the symptoms have returned. 5.20.7 covers reporting the post-operative knee.

Imaging then has to separate retained bodies from new ones, and it cannot, so the pre-operative map is what answers it. 5.20.1 covers structured reporting.

Recurrent disease with cartilage loss is a different problem from recurrent bodies in a preserved joint. 5.3.17 covers joint space narrowing.

Malignant transformation is reported in long standing disease, so a change in character rather than in number is the thing to watch. 5.13.7 covers bone tumours.

Serial imaging is the follow-up, and it needs one protocol to be comparable. 5.5.1 covers the standard protocol.

The useful report gives the number, the distribution by compartment and recess, the calcification, the cartilage, and any aggressive feature. 5.20.1 covers structured reporting.