Case 21 - Transverse trochlear ridge versus osteophyte or post-traumatic deformity

Summary

Imaging description

The trochlear groove is the large curved depression that articulates with the trochlea of the humerus. At the junction of the olecranon and coronoid process there is an osseous ridge without cartilage in this trochlear groove called the trochlear ridge (Figure 21.1). This cartilage-free ridge can project above the articular surface of the trochlear groove by approximately 2–5 mm in 68% of the population. When a trochlear ridge is present, it does not cause impediment to smooth motion at the elbow and it does not decrease the range of motion at the elbow. However, when it approaches 3–5 mm in size it can be mistakenly confused for a central osteophyte (Figure 21.2). It has signal and morphologic characteristics of an osteophyte with projection from the articular surface with both cortical and medullary bone signal characteristics.

Importance

The trochlear ridge can be mistaken for a central osteophyte leading to an erroneous diagnosis of osteoarthritis if no other osteophytes are present and the joint space is still preserved. An erroneous diagnosis of osteoarthritis can lead to an incorrect assumption that the patient's elbow pain is from the incorrectly diagnosed osteoarthritis. Familiarity with the classic location of the trochlear ridge will help prevent this pitfall in interpretation.

Typical clinical scenario

A middle-aged patient presents for MR imaging with a history of chronic elbow pain of unknown etiology. The trochlear ridge should not be identified as a central osteophyte and thus lead to an erroneous diagnosis of osteoarthritis. This ridge of the trochlear groove should not be misconstrued as pathology and reported as a possible cause of the patient’s elbow pain.