An internal bracing system is disclosed for stabilizing a joint such as the knee, shoulder, ankle or the like. The internal bracing system includes an extra-articular tension band mechanism and an anchor assembly therefore. The internal bracing system adds substantial control to unstable joints which is effective in limiting the pathological joint motions and internal slippage. The anchor anchoring assembly designed to affix a tethering device to various bony structures which form a joint, for the purpose of providing stability. The anchor assembly includes an anchor and a set screw. A double helix thread/chamber structure between the anchor and set screw securely holds the tether without binding.