Loading at the distal forearm has been previously examined under static loads, however there remains no consensus on how loading is affected by active wrist and forearm motion. This work examines load magnitudes and load sharing at the distal radius and ulna during of active wrist and forearm motion. Two instrumented implants were designed to measure in vitro loading in cadaveric specimen. The implants were evaluated and found reliable for use in further biomechanical studies. An in vitro study investigated the effect of joint angle and direction of joint motion on loads in the distal radius and ulna during active flexion-extension, radioulnar deviation and dart throw motion. Loads through the distal radius and ulna were significantly greater in extension and reverse dart throw motion than in flexion and forward dart throw motion. A subsequent study examined the effect of radial length changes, joint angle and direction of motion on distal radius and ulna loading during active forearm rotation. Load magnitudes through the distal radius were greater in supination than in pronation. Radial lengthening found to increase radial loading and decrease ulnar loading and radial shortening decreased distal radius loading and increased distal ulna loading throughout forearm rotation, in a quasilinear fashion. This work improves the understanding of forearm bone loading and will assist clinicians in the development of rehabilitation techniques, surgical protocols and implant designs.