Predisposing factors for torsion testis are: *Inversion of the testis. *High investment of the tunica vaginalis which acts like a mesentry through which testis rotates. Here testis hangs like a clapper in bell. *Presence of gap between the body of the testis and epididymis, as a result of which testis twists over epididymis. *Heavy straining often ppts torsion d/t vigorous contraction of the cremaster which is attached spirally. Reference : page 1082 SRB's manual of surgery 5th edition