Sprains are tears of the ligaments and capsules (tissues around joints). Ligaments are made up of bundles of somewhat elastic, collagen tissue and attach one bone to another. Capsules typically partially or completely surround a joint. In a synovial joint, there is lubricating and nourishing fluid within the capsule called synovial fluid.
Like strains, sprains are classified as grade I, II, or III in their severity.
A grade I sprain involves a minimal number of ligament fibers. There may be pain, swelling, and only mild loss of function.
A grade II sprain is a moderate or partial ligament tear. There is usually moderate to severe pain, swelling and bruising are typically present, and there is a loss of joint function (e.g., it is extremely difficult or you are unable to walk on a grade II ligament sprain of the ankle).
A grade III sprain is a complete tearing of the ligament or joint capsule into two pieces. Severe pain, swelling, bruising, and loss of function are associated with a grade III sprain. As with grade III strains, orthopaedic intervention/surgical repair may be necessary.