Current classification of muscle injuries

It has long been recognised that muscle injuries occur at several specific anatomical locations within the muscle–tendon unit. There has been much interest in the grading and classification of muscle injuries with several recent publications proposing different classification systems.1 The British Athletics Muscle Injury Classification system (BAMIC) described four grades of injury with each grade being subcategorised according to an ‘a–c’ injury based on the anatomical location involved. The ‘a’ reflecting a myofascial, ‘b’ musculotendinous and ‘c’ intratendinous injury.2

Limitations to current classification systems

The anatomical description of ‘a–c’ injury within the BAMIC system has led to some variation in clinical practice as to how different radiologists classify injuries as BAMIC ‘a’ or ‘b’ or ‘c’. This confusion may arise due to a lack of clarity on the precise terminology of the connective tissues. While there is some debate in the anatomical literature on the precise definition of fascia, it is generally accepted that fascia, aponeuroses and tendons represent a continuum of musculoskeletal connective tissue in terms of increasing thickness and regularity of collagen fibre orientation, respectively, (tendon>aponeurosis>fascia).3 4 Similar to tendons, but not fascia, aponeuroses have more regularly oriented fibres, which reflects their role in resisting largely unidirectional tensile forces. Table 1 provides more information on the nature of these structures.5 6 Aponeuroses are often underappreciated on imaging due to their thinner nature relative to tendons despite their important function.

A good example of the confusion in terminology of myofascial versus myoaponeurotic versus musculotendinous junction injury in clinical practice is …