The quadriceps are a group of four powerful muscles located at the front of the thigh responsible for flexing the hip and extending the knee. A quadriceps strain occurs when a sudden contraction of the quadriceps causes a pull or rupture of the muscle fibres. Some predispositions to a quadriceps strain injury include over tight quadriceps, inadequate warm up or stretching before a sporting activity, or a muscle imbalance between the quadriceps of the other leg (e.g. leg length deficiency). A quadriceps strain typically presents as a sudden pulling pain in the anterior (front) of the thigh following a sprint, powerful kick or sudden stop.