Traditionally, ankle sprains are classified as grade I to grade III based on clinical signs and loss of function: Grade I sprains originate from mild stretching of the ligaments with only subtle tears. The patient has mild swelling and pressure pain. There is no joint instability on examination, and the patient is able to bear weight and walk with only mild pain. Because of the milder nature of this injury, it is rarely seen in the clinic. A grade II sprain is a more severe injury involving an incomplete tear of the ligament. The patient has moderate pain, swelling, tenderness and bruising. Examination may reveal the presence of mild to moderate joint instability, some limitation of joint mobility, and loss of function. Pain is present with weight bearing and walking. Grade III sprains involve a complete tear of the ligament. The patient has severe pain, swelling, tenderness and bruising. Examination may reveal significant mechanical joint instability, as well as significant functional and motor loss. The patient is unable to bear weight or walk. Although higher grade sprains involve more severe ligament damage, the time required for rehabilitation is not necessarily proportional to the grade of the sprain.