(L. straight + femur) This muscle of the quadriceps group follows a straight line down the front of the thigh originating from the anterior spine of the pelvis and attaches to the tibial tuberosity via the patellar tendon. The rectus femoris is the only quad to cross both the hip and knee joint making it a hip flexor as well as a knee extensor muscle. This muscle is vital to knee joint stability in walking and running. It is most susceptible to blows or trauma because of its location front and center of the thigh. Other common sports injuries include: “Jumper’s knee” and partial tears.