An athlete to you complaining of left anterior thigh pain after doing step back lunges during a weight training session. she states she did heavy squats that same day which was 2 days ago. you find increased muscle tone at mid-thigh with pain upon palpation. she has difficulty performing an air squat as well as a lunge. she cannot extend her knee against manual resistance because of pain. she has never felt this before. what is she suffering from?