Intraarticular pressure distribution in the talocrural joint is related to lower leg muscle forces

Background It is of paramount importance to know the magnitude and the distribution of joint contact stress within the most heavily loaded structures of the human foot. In the talocrural joint role of external loading and loading applied by muscles on joint contact stress is not extensively studied. The purpose was to determine the distribution of joint contact stress of the talocrural joint with varying axial tibia loading and extrinsic tendon loading. Methods Five cadaveric feet were studied in the intact condition and following transsection of ligaments under seventeen different loading conditions. Joint contact stress was determined from capacitive pressure sensors implanted in the talocrural joint when the specimens were loaded in a specially designed loading simulator. Different axial tibia and extrinsic tendon loads were applied. Motions of the bony structures were assessed by an optical motion analysis system. Findings The anterior aspect of the joint is predominantly stressed in all loading conditions. The influence of muscle force on the internal joint contact stress distribution is higher than the axial shank loading. The biggest effect on joint contact stress was initiated by the tibialis posterior muscle. The flexor hallucis homogenizes the pressure distribution in intact joint conditions. Joint angles were not substantially changed by muscle force applications. Interpretation The functions of the muscles of the lower leg are important for maintaining physiologic joint contact stress. Reducing the force potentials of certain muscle tendon units through surgeries, immobilization, fatigue or inappropriate footwear should change the joint contact stress. Such information is helpful to understand the physiological function of the foot. It might also explain the development and manifestation of certain foot pathologies.