Penetrating wounds of joints are treated on the same lines as compound fractures. If the penetrating instrument is to be regarded as infected,--as, for example, when the spoke of a motor bicycle is driven through the upper pouch of the knee,--the injury is to be looked upon as serious and capable of endangering the function of the joint, loss of the limb, or even life itself. Reliance is chiefly laid on primary excision of the edges and track of the wound, and other measures employed in the treatment of gun-shot wounds. While the wound in the synovialis and capsule is sutured, that in the soft parts is left open. If drainage is employed, the tube extends down to the opening in the synovialis, but not into the joint itself. If sepsis supervenes, the joint is opened and irrigated by Carrel's method. Some form of splint and a Bier's bandage are valuable adjuncts. The final recourse is to amputation. #Gun-shot injuries# of joints vary in severity from a mere puncture of the synovial layer by a chip of shell to complete shattering of the articular surfaces. Between these extremes are cases in which the capsular and synovial layer are extensively lacerated without involvement of the bones, and others in which the bones are implicated without serious damage being done to ligaments or synovial layer--for example, by a bullet passing through and through the cancellated part of one of the constituent bones, or by a fissure extending into the articular surface. In all degrees the great risk is from septic infection, which may be assumed to be present in all but the last-named variety. The _treatment_ consists in immediately cleansing the wound by excising grossly damaged tissue and removing any foreign body that may have lodged; disinfecting the exposed part of the joint cavity with eusol, "bipp," or other antiseptic, and closing the wound or establishing drainage, according to circumstances. The joint is then immobilised till the wound has healed, after which massage and movement are commenced. When the bones are shattered or when sepsis gets the upper hand and disorganises the joint, amputation is called for. #Sprains.#--A sprain results from a stretching or twisting form of violence which causes the joint to move beyond its physiological limits, or in some direction for which it is not structurally adapted. The main incidence of the force therefore falls upon the ligaments, which are suddenly stretched or torn. The synovial layer also is torn, and the joint becomes filled with blood and synovial fluid. Muscles and tendons passing over the joint are stretched or torn, and their sheaths filled with serous effusion. It is not uncommon for portions of bone to be torn off at the site of attachment of strong ligamentous bands or tendons, constituting a "sprain fracture"; or for intra-articular cartilages to be torn and displaced, as in the knee.