Classic history and presentation: Because isolated injury to the LCL is rare, LCL lesions most commonly present in conjunction with feelings of instability and dull pain in the affected knee. The knee may or may not be swollen, depending on the chronicity and mechanism of the injury. LCL tears are also often associated with peroneal nerve damage (foot drop and/or numbness on the dorsum of foot) because it courses superficially in the lateral knee. Injury may present acutely (< 3 weeks) or chronically (> 3 weeks), with chronic cases having a greater risk of degenerative changes in the knee secondary to instability.
Prevalence: Because of frequent concurrent injury, it has been speculated that PLC pathologies are underreported and undertreated. A large 10-year study of more than 17 000 European athletes with sports-related injuries showed that approximately 37% experienced injury to the knee. Only 1.1% of knee injuries involved lesions of the LCL.
- Age – Nearly 65% were between 20 and 39 years, with the 20-29 year age group comprising nearly 45% of patients.
- Sex / gender – Nearly 70% of patients with knee injuries were male.
Grade / classification system: The grade of an LCL injury is determined by the amount of lateral joint line opening with varus stress:
- Grade 1 – less than 5 mm
- Grade 2 – 5-9 mm
- Grade 3 – 10 mm or more