Purpose of the study: Mycetoma designates an inflammatory pseudotumour caused by fungal or bacterial agents with a slow chronic course and characterised by the emission of species-specific grains through fistules. Like the foot, the knee is a weight-bearing zone which can lead to mycetoma of soft tissue and/or bone or articular tissue. The purpose of this work was to study the frequency of the different clinical forms and report medical and surgical outcomes of the localisation.

Material and methods: This was a retrospective analysis of consecutive files collected over a 20-year period from July 1988 to 2008 including a total of 267 cases. Twentyfive patients (22 male 3 female) had an articular or peri-articular mycetoma of the knee joint. Mean age was 31.8 years (range 18–59). The right knee was involved in 17 cases and the left in eight. Duration of symptoms was 2.2 years (range 1–25 years). Antibacterial treatment with sulfamethoxazole and exclusively for actinomycetoma was given for 10 months at least and antifungal treatment with ketoconazole as adjuvant treatment with surgery for maduromycetomas. This orthopaedic surgery was radical (three above-knee amputations) or conservative (directed healing for 5, first-intention surgery for 5 with a flap for 3 and with a graft for the others).

Results: The knee accounted for 9.23% of the localizations in our series, most common after the foot and ankle. Twenty cases were exclusively maduromycetomas with black grains; the five others were actinomycetomas: 3 red grain, 1 white grain and 1 yellow grain. The topographic forms were predominantly anterior localization: 15 cases (versus popliteal in two, the entire knee in four and unknown in four). According to the Bouffard classification, the lesions were: diffuse (n=20), polyfisutulised (n=20), sclerohypertrophic (n=1) versus two localized encapsulated forms. Local spread led to bone and joint involvement in six patients, mycosis arthritis in three complicated by a pathological fracture of the patella. At last follow-up, there have been three recurrences with limited flexion in four patients.

Discussion: Articular or extra-articular mycetoma of the knee is an infectious dermato-orthopaedic disease dominated by fungal infection. Treatment is particularly difficult in advanced stage disease, medical and surgical management can be proposed with cancerological type resection.