Stephen Curry recently suffered an medial collateral ligament (MCL) knee injury. MCL injuries are classified into 3 categories.
Grade 1: Mild injury with no loss of ligament integrity (stretch injury).
Grade 2: Moderate injury with partial tearing of the ligament and some resulting knee laxity.
Grade 3: Severe injury with complete disruption of the ligament and gross knee laxity.
The diagnosis can be made based on history and physical exam (valgus test by stressing the MCL). The more significant the injury, the more knee gapping there is on stress examination (equal or greater than 1cm indicates a grade 3 injury). An MRI is used for confirmation of injury severity and also to identify other potential injuries (such as ACL or meniscus tear).
Most MCL tears can be treated non-operatively. Treatment involves knee bracing and time off (ranging from 2-8 weeks depending on injury severity) sporting activities. MCL repair or reconstruction is performed when there are other concomitant injuries and/or when there is persistent knee instability.
This is more commonly the case in grade 3 injuries. Fortunately, the reigning MVP only suffered a grade 1 MCL sprain and should make a rapid, full and uneventful recovery with bracing and a few weeks off.