Introduction: In spite of the common occurrence of hallux valgus deformity and the multiple corrective procedures that have been proposed, only few studies have been published about the anatomy of this joint. None of these studies mention the existence of a meniscal structure in the first MTP joint. The fact that this structure is often seen during bunion surgery evoked this study.

Material and methods: A hunderd and two human cadaveric feet were dissected primarly to study the anatomy of the first metatarsophalangeal (MTP) joint. The anatomical findings on the specimens were correlated with clinical findings on 100 consecutive hallux valgus procedures. Particular attention was paid to the localization and histology of this meniscal structure. Based on this study, possible associations between the presence of this structure and the pathophysiology of the hallux valgus deformity and chondral lesions are proposed.

Results: A meniscal structure was present in 19 percent of the cadavers. A striking negative correlation is found between the presence of a meniscus and the extent of chondral lesions (P < 0.05). The presence of the meniscus was higher in cadavers with hallux valgus deformity (33%), however no significant correlation is found between the occurrence of hallux valgus deformity and the presence of this meniscus (P = 0.2). In our clinical study this meniscus was seen in 40% and was particularly high in younger patients with mild -painful-bunions.

Conclusions: The presence of this meniscal structure seems to stabilize the MTP joint, preventing hallux valgus (or rotational ) deformities. Once the rotational deformity increases the meniscus tears becomes painful and slips into the joint. In the more advanced hallux valgus deformity this meniscus plays little function and seems to disappear, leading to arthrosis.