Brief Answer: These can be caused by knee injury. Detailed Answer: Hello, Thanks for your query. Osteoarthritis and medial synovial plica can be caused by knee injury. Medial synovial plica, is the synovial tissue most prone to irritation and injury. When the knee is flexed, the plica is exposed to direct trauma, but it also may be injured in overuse syndromes. Repetitive stress injuries can develop osteoarthritis of the knee because of the constant pressure on the joint. I do hope that you have found something helpful and I will be glad to answer any further query. For future query, you can directly approach me through my profile WWW.WWWW.WW Take care

---