The forearm is a complex articular unit, with poorly understood biomechanics. A novel forearm simulator to facilitate physiologic testing of cadavers for multiple clinical scenarios was designed, manufactured and validated. The simulator had good repeatability and reproducibility. A number of outcome measurements were potentiated including the forearm’s resistance to rotation, radiocapitellar contact pressure and area as well as Interosseous Membrane (IOM) loads. Testing of changes to forearm biomechanics due to radial head excision and variations of radial head arthroplasty dimensions was conducted. Radial head arthroplasty using the correct radial head length and diameter recreated the biomechanics of an intact forearm. Radial head excision as well as an implant of nonanatomic length or diameter created abnormal radiocapitellar joint properties and load transfer within the forearm. If radial head arthroplasty is clinically required, an implant that is similar in dimensions to the native radial head maintains native forearm biomechanics.