किसी अस्थिसंधि (ज्वाइंट) के स्नायु (लिगामेन्ट) जब अपनी क्षमता से अधिक खिंच जाते हैं तो इस प्रकार की चोट को मोच (sprain) कहते हैं। चोट लगने के साथ ही सूजन शुरू हो जाती है। मोच किसी भी जोड़ में हो सकता है पर एड़ी और कलाई के जोड़ पर ज्यादा मोच आती है।

A sprain is a soft tissue injury of the ligaments within a joint, often caused by a sudden movement abruptly forcing the joint to exceed its functional range of motion. Ligaments are tough, inelastic fibers made of collagen that connect two or more bones to form a joint and are important for joint stability and proprioception, which is the body's sense of limb position and movement. Sprains may be mild, moderate, or severe, with the latter two classes involving some degree of tearing of the ligament. Sprains can occur at any joint but most commonly occur in the ankle, knee, or wrist. An equivalent injury to a muscle or tendon is known as a strain.