Les auteurs présentent 4 observations de luxation irréductible du genou par incarcération du plan capsulo-ligamentaire médial dans l'échancrure inter-condylienne. Ces luxations, parfois désignées sous le terme de lésions en boutonnière du condyle fémoral médial à travers la capsule, sont très rares. L'examen clinique permet de reconnaître des signes traduisant l'irréductibilité. Ces signes sont : un sillon en regard de l'interligne fémoro-tibial médial, un bourrelet en arrière du condyle médial. Une lésion artérielle associée doit être éliminée. Une complication est spécifique à ce type de luxation, la nécrose cutanée. Ce risque impose une réduction en urgence par abord chirurgical ; l'arthroscopie est déconseillée dans ce type de lésion capsulo-ligamentaire car il existe un risque potentiel de syndrome des loges.

Irreducible dislocation of the knee is exceptional. Incarceration of the capsulo-ligamentary elements in the inter-condylar notch is a particular causal mechanism. We report four new cases and review the literature to describe the diagnostic and therapeutic approach.

Between January 2001 and January 2002, four patients underwent surgery after trauma (wind surf, ski accidents) producing an irreducible knee dislocation. Mean patient age was 53 years and mean follow-up was 16 months. The IKDC classification was used to assess outcome.

Physical examination revealed characteristic signs: a groove facing the medial joint line with signs of cutaneous suffering just above and a fold line behind the medial condyle. Orthopedic reduction failed. Surgery was performed in all cases and revealed incarceration of the entire capsulo-ligamentary structure in the intercondylar notch with the medial condyle in an extra-articular position. After surgical reduction, healing was achieved in all cases without cutaneous necrosis. The mean subjective IKDC score was 53.9.

Orthopedic reduction is impossible in about 4% of all cases of knee dislocation. Clinical signs are characteristic when the medial capsulo-ligamentary structures are incarcerated in the intercondylar notch; the anatomic injury is almost always the same. Vasculonervous complications are exceptional but an emergency arteriography should be obtained to rule out an infra-clinical intimal lesion. Cutaneous necrosis is a specific complication of irreducible dislocation. Early and complete reduction is required to prevent necrosis. Arthroscopic management raises the risk of compartment syndrome since peripheral lesions are not healed. Satisfactory functional recovery requires associated repair of the cruciate ligaments.

This type of irreducible dislocation of the knee is a specific clinical entity. It usually results from postero-lateral rotation but may exceptionally occur after lateral dislocation. A groove associated with a fold line indicates the need for rapid surgical reduction to avoid the risk of cutaneous necrosis.