Thigh pain can be caused by a wide range of problems. Pain can be referred to the thigh from a problem in the abdomen, low back, hip, or knee. For example, kidney stones, tumors, or blood clots can cause thigh pain.
But muscle strains, bursitis, pressure on the nerve, and hernias can also cause thigh pain. It is also possible that a problem with the implant can send pain to the thigh. Loosening of the implant, infection, and wear debris from the implant can cause thigh pain.
A simple X-ray can help show what might be going on. First, the radiologist will look for fractures. Rotation of the femur (thigh bone) indicates loosening of the implant. The X-ray can also show subsidence or sinking of the implant down into the bone.
Don't put off having this problem checked. Early diagnosis and treatment can prevent more serious problems later. It could be something as simple as muscle weakness or even a problem with posture. If this is the case, a physical therapist can help your mother with a program of exercise and posture awareness. More serious problems can be addressed by the surgeon.