Common Origin Tendon of the Biceps Femoris and Semitendinosus Muscles, Functional and Clinical Relevance

Abstract

The injury of Biceps Femoris long head (BFlh) and Semitendinosus (ST) is caused by over-stretch of the muscles at the back of the thigh. This condition encompasses almost one third of sports-related injuries and has severe consequences, such as pain and weakness of the muscles. This injury is related namely to quick and demanding activities, such as short distance sprinting in a limited time period. The Common Origin Tendon (COT) for these two muscles is affected in these injuries. This tendon is formed by the BFlh and ST muscles which together have a common origin in the ischial tuberosity. Given the lack of complete knowledge about the detailed structure of the COT, we dissected cadaveric limbs, describing their morphological characteristics, and discussing its functional and clinical implications.: Thirty-five human cadaveric lower limbs were dissected after fixation to analyze the morphology of the COT, focusing on their volume and muscular/tendinous proportion. We identified two subtypes of COT. The most frequent was the musculotendinous type, in which the origin of the BFlh was mainly tendinous, while the ST muscle was mainly muscular (91.4%). In the tendinous type both muscles had a tendinous origin (8.6%). In the musculotendinous type, the ST muscle ends with a microscopic connective tissue that extend into the ischial tuberosity. We conclude that there is a variability in the anatomical presentations of the COT, and we propose that this will correspond with biomechanical differences in the risks and the response to regional injuries. The connective tissue between the COT and the neighbouring structures could be a risk factor for adhesion tearing.

Morphological study on the origin of the semitendinosus muscle in the long head of biceps femoris

“…During a previous study focused on the morphology of the conjoint tendon, it was observed that part of the fibers of semitendinosus originate from the long head of biceps femoris caudally to the conjoint tendon 15 . This origin has been observed previously by other authors.…”

“…In intrinsic hamstring injuries, the long head of the biceps femoris is usually affected in a region located approximately 67 mm caudal to the ischial tuberosity 7,9,10 . From our observations, this position corresponds to the location where the long head of the biceps femoris and the semitendinosus muscle meet to form a conjoint hamstring tendon 15 . The connection between these two muscles could be implicated in the pathogenesis and characteristics of injuries affecting this area.…”

“…The morphology of the conjoint tendon and its insertion surfaces in the ischial tuberosity, have been investigated by several authors 15–19 . Other works have described the muscle partition of hamstrings, the pennation angle, and other morphometric parameters of the muscle fibers 20–23 .…”