M. articularis genus. Observations on arrangement and consideration of function.

On the basis of 44 adult Japanese cadavers, the mode of origin, insertion and innervation of the articularis genus muscle (m. articularis genus: AG) is described. All the muscle bundles that are inserted into the posterior aspect of the synovial membrane of the joint capsule as well as the suprapatellar bursa are defined as AG. The inserting fibers spread medially and laterally over the subsynovial connective tissue which is the outer layer of synovial membrane facing the femur. The fatty tissue between each muscle bundle gradually increases with depth. A few deeper muscle bundles of AG seem to be separated by a layer of fat from those of the superficial layer. The deepest muscle bundles arise from the anterior surface of the femur at a slightly lower level than the proximal apex of the suprapatellar bursa. It is inserted into the synovial membrane at the level of the junction of the suprapatellar bursa and proper joint cavity when the knee is extended. It is difficult to distinguish AG from m. vastus intermedius (Vi) only on the basis of the manner of origin and the surrounding fatty tissue. The innervation is in common with that of Vi, namely, a few nerves which run down obliquely to the lower medial part of Vi.