This paper presents a wearable measurement system for patients recovering from a hip replacement operation. The system, called HipGuard, is intended to be used at home during the recovery period of eight to 12 weeks after the surgery. The system measures the posture of the patient and also monitors the load put on the operated leg. These measurements help the patient to follow the precautions given by the surgeon. The measurement system consists of seven wireless posture sensor nodes for measuring the orientation of the hip and the legs, and a wireless load sensor node for measuring the load put on the operated leg. The patient is informed by the HipGuard system with an audio signal or a haptic vibration if the position of the operated hip or the load put on the operated hip approaches set limits.