A condition common in growing children where the kneecap remains in two pieces
The kneecap (patella) normally forms from several small bone centers that fuse together as a child grows.
In some people, these centers don't fully fuse, leaving the kneecap in two or more separate pieces. This is bipartite patella.
It occurs in about 0.2–2% of people. Most live their entire lives without any symptoms, but sports and overuse can cause inflammation at the separation line, leading to pain.
During fetal development through adolescence, bone centers fail to merge completely
Jumping, sprinting, and other knee-stressing activities cause repeated friction at the separation
Repeated irritation causes surrounding inflammation and pain
Most patients improve within 4–12 weeks of conservative treatment and can return to sports. Rehabilitation focusing on quadriceps and hip function is key to preventing recurrence.
Surgery is considered only when at least three months of conservative care has not helped. Most people settle down with conservative care alone.
Options include removing the separated fragment (excision) or fixing it in place (internal fixation). It's important not to self-diagnose, as it must be distinguished from kneecap fracture and other conditions.