#Hernia of Muscle.#—­This is a rare condition, in which, owing to the fascia covering a muscle becoming stretched or torn, the muscular substance is protruded through the rent.  It has been observed chiefly in the adductor longus.  An oval swelling forms in the upper part of the thigh, is soft and prominent when the muscle is relaxed, less prominent when it is passively extended, and disappears when the muscle is thrown into contraction.  It is liable to be mistaken, according to its situation, for a tumour, a cyst, a pouched vein, or a femoral or obturator hernia.  Treatment is only called for when it is causing inconvenience, the muscle being exposed by a suitable incision, the herniated portion excised, and the rent in the sheath closed by sutures.

#Dislocation of Tendons.#—­Tendons which run in grooves may be displaced as a result of rupture of the confining sheath.  This injury is met with chiefly in the tendons at the ankle and in the long tendon of the biceps.

Dislocation of the peronei tendons may occur, for example, from a violent twist of the foot.  There is severe pain and considerable swelling on the lateral aspect of the ankle; the peroneus longus by itself, or together with the brevis, can be felt on the lateral aspect or in front of the lateral malleolus; the patient is unable to move the foot.  By a little manipulation the tendons are replaced in their grooves, and are retained there by a series of strips of plaster.  At the end of three weeks massage and exercises are employed.

In other cases there is no history of injury, but whenever the foot is everted the tendon of the peroneus longus is liable to be jerked forwards out of its groove, sometimes with an audible snap.  The patient suffers pain and is disabled until the tendon is replaced.  Reduction is easy, but as the displacement tends to recur, an operation is required to fix the tendon in its place.  An incision is made over the tendon; if the sheath is slack or torn, it is tightened up or closed with catgut sutures; or an artificial sheath is made by raising up a quadrilateral flap of periosteum from the lateral aspect of the fibula, and stitching it over the tendon.

Similarly the tibialis posterior may be displaced over the medial malleolus as a result of inversion of the foot.

The long tendon of the biceps may be dislocated laterally—­or more frequently medially—­as a result of violent or repeated rotation movements of the arm, such as are performed in wringing clothes.  The patient is aware of the displacement taking place, and is unable to extend the forearm until the displaced tendon has been reduced by abducting the arm.  In recurrent cases the patient may be able to dislocate the tendon at will, but the disability is so inconsiderable that there is rarely any occasion for interference.

#Wounds of Muscles and Tendons.#—­When a muscle is cut across in a wound, its ends should be brought together with sutures.  If the ends are allowed to retract, and especially if the wound suppurates, they become united by scar tissue and fixed to bone or other adjacent structure.  In a limb this interferes with the functions of the muscle; in the abdominal wall the scar tissue may stretch, and so favour the development of a ventral hernia.