The anterolateral ligament of the knee: a radiologic and histotopographic study.

Purpose: Recent anatomic investigations of the lateral structures of the knee have rediscovered a ligament, called the antero-lateral ligament (ALL).

Methods: Ten specimens of ALL (6 M, 4 F, mean age 82.3) were sampled from bodies of the Body Donation program of the University of Padova for histological and immuno-histochemical studies. Moreover, a retrospective magnetic resonance (MR) study was carried out in 50 patients (30 M, 20 F, mean age 37.5). MR exams with a normal anatomo-radiological report were selected.

Results: From the microscopic point of view the ALL corresponds to a dense connective tissue (mean thickness 893 ± 423 µm), and is composed by collagen I (90 %), collagen III (5 %) and collagen VI (3 %) and scarce elastic fibers (<1 %). On MR exams, ALL appears as a thin linear structure, originating at the lateral epicondyle, running obliquely downwards and forwards, and inserting in the middle third (46 %) or inferior third (14 %) of lateral meniscus and in the lateral aspect of the proximal tibia. It was observed in 47 cases (93 %), with a mean length of 32 ± 4.6 mm and mean thickness of 1.1 ± 0.4 mm. The ALL showed low signal intensity on both T1- and T2-weighted sequences.

Conclusion: The ALL shows the typical structure of a fibrous ligament. From the anatomo-radiological point of view the ALL is almost constantly depicted by routine 1.5-T MR scan.