The posterior compartment of the thigh is composed of three major muscles collectively known as the hamstring muscles. These consist of the biceps femoris short and long head, semimembranosus and semitendinosus. Excluding the short head of biceps femoris, the hamstrings contribute to the movement of the hip and the knee joints as they span across both joints.

Imaging findings or procedure details:

100 pelvic MRIs in patients under the age of 40 years were reviewed by musculoskeletal radiology fellow and a consultant musculoskeletal  radiologist with more than 10 years’ experience in musculoskeletal radiology.  
P value using an unpaired t test was less than 0.05 confirming that the difference in the vector angle of the different hamstring components was statistically significant. 
Applying the concept of Newton’s second law to the angles calculated we demonstrated that an increase of 9% force applied to the conjoint tendon origin when compared to the semimembranosus tendon. 

Our hypothesis is that the nature of the conjoint tendon -ischial angle predisposes to an increased risk of tearing in this hamstring component. This might be one of the reasons for the difference in the incidence and patterns of the injuries of the various muscles of the hamstrings.

Proximal hamstring origin architecture- defining the vector angle