Bipartite patella

Case contribution: Dr Radhiana Hassan

Clinical:

• A 71 years old man
• Underlying hypertension and IHD
• Complaint of right knee pain
• History of twisting knee with mild swelling
• Able to ambulate without aid

Radiographic findings:

• There is a well-defined linear line seen at superolateral aspect of right patella (yellow arrows) separating the patella.
• The line has well corticated bone borders
• No displacement of the bone fragment
• No associated soft tissue swelling at knee region

Diagnosis: Bipartite patella

Discussion:

• A bipartite patella is a patella with an unfused accessory ossification centre at the superolateral aspect.
• Prevalence of bipartite patella is about 2% of population
• It occurs bilaterally in about 43% of cases.
• It is more common in male than females.
• Mostly are asymptomatic but patient can present with knee pain after trauma or overuse.
• Different location: superoplateral portion (75%), lateral margin (20-25%) and inferior pole (1%).
• Differentiation with fracture; most common patella fracture is transverse (linear fracture is very uncommon), fracture commonly occurs after direct trauma to knee and  volume of fracture fragment usually equivalent of normal patella