Lateral Collateral Ligament Ganglion Cyst or Meniscal cyst?

Mr Tan came with a localised swelling in his right knee since 4 years ago. He told me that he landed awkwardly and subsequently a month later a swelling progressively developed. He would have pain with jogging or sitting cross-legged. He had seen an Orthopaedic surgeon who told him to undergo Arthroscopic surgery to determine the extent of damage.

I examined his knee and found that he had normal range of motion and his ligaments were all intact. He only localised tenderness over the 2cm by 2cm cystic swelling which appeared to be arising adjacent to the lateral collateral ligament and lateral meniscus. His tests for meniscus were inconclusive. I have referred him for another Orthopaedic surgeon for a thorough work-up (X-ray and MRI Right knee).

Since he is usually asymptomatic, if the swelling does not affect his normal function I would tend to leave the swelling alone.