- Bipartite patella is an asymptomatic anatomical variant.
- Occasionally, some adolescent athletes can present with AKP, resulting in decreased participation and performance.
- Bipartite patella is classified in type I, inferior pole; type II, lateral margin; and type III, superior lateral pole, depending on where the accessory patellar fragment is.
- Nonoperative treatment is advocated first. If symptoms persist surgical treatment should be attempted.
In 2% to 3% of the general population, the finding of bipartite patella on knee radiographs is often incidental.1,2 During development, the patella normally originates in a primary ossification center. Occasionally, secondary ossification centers emerge around the margins of the primary center and typically join that center. In some cases, the secondary2 center remains separated, leading to patella partita and an accessory patellar fragment.3,4
The bipartite patella is connected to the primary patella by fibrocartilage. The fibrous attachment may become irritated or separated as a result of trauma, overuse, or strenuous activity.1,5-7 Saupe classification of bipartite patella is based on accessory patellar fragment location: type I, inferior pole; type II, lateral margin; and type III, superior lateral pole.8 When an individual with a bipartite patella becomes symptomatic, anterior knee pain (AKP) is the most common complaint—it has been described in adolescent athletes in numerous sports.7,9-11For most patients, first-line treatment is nonoperative management. A typical regimen includes reduced activity, use of nonsteroidal anti-inflammatory drugs, physical therapy, and isometric quadriceps-strengthening exercises.1,12 Other nonoperative approaches described in the literature are immobilization,5,10 steroid and anesthetic injection, and ultrasound therapy.13 If symptoms do not improve, surgical treatment should be considered. Surgical treatment options include open excision of fragment,3,9,12 arthroscopic excision of fragment,7,14,15 tension band wiring,5,16 open reduction and internal fixation,17 open or arthroscopic vastus lateralis release,18-20 and lateral retinacular release.21 However, the optimal surgical option remains controversial.
In this case report, we present a modification of an arthroscopic surgical technique for excising a symptomatic bipartite patella and report midterm clinical outcomes. The patient provided written informed consent for print and electronic publication of this report.
A 16-year-old elite male ice hockey player presented to clinic with a 2-week history of left AKP. He could not recall a specific injury that triggered the symptoms. Radiographs were obtained at an outside institution, and knee patellar fracture was diagnosed. The patient, placed in a straight-leg immobilizer, later presented to a referral clinic for a second opinion and further evaluation. Physical examination revealed significant tenderness to palpation of the lateral aspect of the patella. Range of motion was symmetric and fully intact. Patellar mobility was excellent. However, the patient could not perform a straight-leg raise because of the pain.
We obtained anteroposterior and lateral radiographs (Figures 1A, 1B), which showed evidence of a Saupe type III bipartite patella with separation at the superolateral pole.
Two years later, the patient returned with left AKP, again localized to the lateral aspect of the patella, over the bipartite fragment. The pain was significant with compression. Given the patient’s history, arthroscopic excision of the bipartite patella was recommended. After discussing all treatment options, the patient elected to proceed with the surgery.
The patient was positioned supine on the operating table. Medial and lateral parapatellar arthroscopic portals were created. Menisci, cruciate ligaments, and tibiofemoral articular cartilage were arthroscopically visualized and determined to be normal. The bipartite patella was easily visualized, and notably loose when probed. Grade 2 chondromalacia was present diffusely throughout the bipartite patella and on the far lateral aspect of the patella, at the fragment interface.
Attention was then turned to arthroscopic removal of the accessory patellar fragment (Figures 3A, 3B).