This chapter discusses different types of peripheral nerve injuries - including stretch-related injuries, such as hematoma, neuropraxia, axonotmesis and neurotmesis. Several systems are available for classifying nerve injuries. Sunderland’s and Seddon’s classification are commonly used. In neuropraxia, spontaneous recovery usually occurs within 6 to 8 weeks. In axonotmesis, spontaneous improvement may be observed, but in neurotmesis, surgical intervention will be required. Testing of muscles in individual nerve injuries is an important procedure to correctly diagnose the injury, which involves testing of sensation in the affected area. The chapter charts out a detailed table to describe the different various tests that can be done on the muscles to find an injury in a particular type of nerve. Brachioradialis extensor muscles of the wrist joint can be tested to locate an injury in the radial nerves. Other testing methods include conduction studies, such as motor nerve conduction studies, which are performed by electrical stimulation of a peripheral nerve and recording from a muscle supplied by the nerve. The chapter also gives brief introductions to different types of nerves such as the sciatic nerve, peroneal nerve and tibial nerve.