Hence, MRI is the investigation of choice in a clinically suspected lesion with negative radiographs while CT remains the preferred investigation for pre-operative planning with a positive plain radiograph as it better demonstrates the subchondral area of the lesion. Although it provides good visualization of the cartilage, it tends to overestimate the extent of the subchondral lesion due to the associated marrow edema. MRI is the most sensitive imaging for OLT with a sensitivity of 96%. In case of clinically suspected lesion with negative radiographs, advanced imaging options such as CT and MRI are useful. Berndt and Harty classification is the staging system that is widely employed for describing OLT on plain radiographs. Plain radiography is the initial investigation of choice in a clinically suspected case of OLT. This initial evaluation often leads to a broad differential diagnosis including ankle synovitis, impingement, occult fractures, and early ankle/subtalar arthritis. Provocative tests such as anterior drawer test should be performed and compared to the unaffected side to evaluate the associated instability. Clinical examination may reveal effusion at the ankle, tenderness over the talus on palpation, decreased range of motion, and pain on ankle dorsiflexion and inversion. A history of ankle trauma/recurrent instability is to be elicited as OLT are associated with ankle instability. Patients present with spectrum of non-specific complaints including of pain on weight-bearing, swelling, stiffness, and occasionally locking sensation at the ankle joint. All these factors make the talus prone for developing osteochondral lesions. Second, arterial supply to the talar dome and the overlying cartilage is by a retrograde vascular network that comes from the talar neck with additional watershed areas showing poor perfusion in the posteromedial, posterolateral, and mid-medial segments of the subchondral bone. First, the talar cartilage is relatively thinner with a thickness of 0.7–1.2 mm compared to that of other joints of the lower extremity. There are numerous reasons that make the talar cartilage and the subchondral bone prone to vascular insufficiency. These repetitive injuries may result in microtrauma in an already vulnerable bone with sparse vascularity causing OLT. Axial loading with inversion and dorsiflexion has been described as the most common mechanism for lateral lesions while plantar flexion, inversion, and external rotation are possibly the mechanism for medial lesions.
Among the OLT, up to 94% of the lateral lesions are said to be secondary to trauma while only 62% of medial lesions are post-traumatic. Most OLT are secondary to trauma, with up to 50% of ankle sprains resulting in some grade of cartilage injury. There have been numerous changes to the terminology of these lesions since the first description, however, the term “osteochondral lesions of the talus” (OLT) is generally preferred. in 1984 emphasized that these lesions should not be called as osteochondritis dissecans but be grouped under a broader term “osteochondral lesions of the talar dome.” The arthroscopic treatment of these lesions was first described by Parisien and Pritsch et al. They also proposed the radiological classification that is widely employed even to the present day.
In 1959, Berndt and Harty were the first to describe the pathogenesis of osteochondral lesions post-trauma. In 1922, Kappis extrapolated the concept of spontaneous necrosis at the hip to the etiopathogenesis of foreign bodies in the ankle joint and used the term osteochondritis dissecans. The first description of osteocartilaginous loose bodies in the ankle, attributed to trauma, was given by Monro in 1738. This review aims to elucidate the historical aspect of the disease, etiopathogenesis, classifications, diagnosis, and treatment to assist in day-to-day clinical practice. These lesions pose a diagnostic challenge to the attending clinician due to lack of specific clinical signs and lack in consensus regarding treatment makes the management aspect controversial. Although majority may be associated with trauma, some may develop insidiously. This is a broad terminology that encompasses a variety of disorders including osteochondritis dissecans, osteochondral fractures, and osteochondral defects. Osteochondral lesions of the talus (OLT) are those that affect the chondral and subchondral areas of the talus.
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