It hurts where?  
The area of pain will vary according to the severity of the injury.  Acutely there will be generalized pain throughout the medial and lateral aspect of the ankle.  Specific point tenderness will be along the anterior and distal end of the lateral ankle.  Active and passive movement of the ankle joint in all planes will cause discomfort with an increase in discomfort upon inversion and plantar flexion. 

How does it happen?  
As with most joints of the body, there are specific ligaments to prevent excessive motion of that joint.  The anterior talofibular ligament (ATF) and the calcaneofibular ligament (CF) are the primary restraints of ankle inversion.  Because ankle sprains usually occur with the foot in plantar flexion (foot pointed downward) the ATF is the most frequently injured.  With the foot in plantar flexion the ATF is taught.  With combined excessive inversion and plantar flexion, tearing or complete rupture of the ATFL is the usual occurrence.  This exact mechanism may occur with any high intensity activity involving lateral movement, jumping or running.  It may also occur with leisurely walking if the ground surface is uneven (stepping into a hole).  Occasionally, foot abnormalities may predispose an athlete to ankle sprains.  For these athletes orthotics may be required to reduce the risk of further injuries. 

Injury Progression… 
Classification of inversion ankle sprains is done through a grading system according to the amount of damage.  Grade 1 is considered to be mild stretching within the ATF with little swelling, tenderness and laxity.  Grade 2 may vary depending on the source.  Some sources will identify complete rupture of the ATF without CF involvement and others will claim partial tearing of both.  Descriptors of this grade include mild-moderate laxity, moderate pain, moderate inflammation and some loss of motion.  Grade 3 sprains indicate rupture of both the ATF and CF.  Descriptors include severe swelling, an unstable joint, loss of function, and abnormal motion.  As with any injury, improper rehabilitation and early return to competition may cause progression from one grade to the next. 

Similar injuries:  
Upon occurrence of a suspected ankle inversion sprain, bony involvement must also be suspected.  Fractures to the distal end of the fibula as well as avulsion fractures should be ruled out.  Complete immobilization of these fractures must occur for proper bone healing to take place. 

Treatment:  
The treatment process can be divided into three phases.  Modifications to these phases can be made depending upon the severity of the injury.  Phase 1 is usually one to two days with the focus primarily on the reduction of inflammation utilizing the principles of RICE (Rest, Ice, Compression, and Elevation), Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), and crutches as needed to allow weight bearing as tolerated.  Phase 2 (2-12 days) focuses on restoration of motion within the ankle complex starting with active range of motion into dorsiflexion and plantar flexion.  Inversion and eversion may be too painful to tolerate actively and therefore should be performed either passively or active-assist.  Weight bearing during walking should gradually be increased to allow proprioception to return and an increase in ankle mobility.  Phase 3 (12 days and beyond) should focus on strengthening, agility and endurance.  Strengthening should  primarily emphasize dorsiflexion and eversion, as these muscles are responsible for resisting inversion-plantar flexion sprains.  Proprioception activities can be initiated utilizing a BAPS / balance board or trampoline.  Agility and endurance activities should gradually be progressed to allow return to functional and athletic activities.  For certain athletes, the use of an orthotics may help limit the vulnerability of a person to inversion sprains. 

Participation status:  
Returning to competition is dependent again on the severity of the injury.  Some general indicators that may be used as a guideline for return include full muscular control of a painless joint with full active range of motion and minimal to no swelling.  Prophylactic taping and bracing has proven effective in the prevention of ankle inversion sprains and should be incorporated for some time after the initial injury.  Continued strengthening of the ankle musculature and proprioception activities should be continued both in and out of season to allow continued prevention of inversion sprains.