Isolated Lateral Collateral Ligament Injury of the Knee in a Judo Athlete: A Surgical Case Report.

Introduction: We report a rare case of surgical treatment for an isolated lateral collateral ligament (LCL) injury of the knee that was difficult to correctly diagnose considering physical findings alone of a judo athlete.

Case Report: The 27-year-old man complained of pain on the lateral side of the right knee and discomfort and balance instability when climbing and descending stairs. During a judo match, he stepped on his right foot to prevent his opponent's waza (techniques), causing forced varus on his knee in a slight flexion position. His right knee showed no apparent sway in the manual test, but pain around the fibular head was induced in the figure-of-four position, and the LCL could not be palpated. Joint instability was not detected on varus stress roentgenography, but magnetic resonance imaging showed signal changes and an abnormal course in the fibula head insertion at the distal part of the LCL. Although no instability was observed objectively, clinical findings diagnosed LCL as an isolated injury, and surgical treatment was performed. Six months after the operation, his symptoms improved, and he resumed competing in judo.

Conclusion: To correctly diagnose an isolated LCL injury of the knee, it is important to consider patient history and physical findings. Repair of the injury could improve subjective symptoms, such as pain, discomfort, and balance instability, even if objective instability is not observed.