per 100,000 people. Fithian defined the highest risk to be amongst females aged 10 to 17 years old. And we know that there are a number of predisposing anatomic risk factors that contribute to this. The Wall and Lehner found up to a 70% risk of recurrence in patients with open growth plates and trochlear dysplasia. Management of first-time dislocations without loose body or fracture have typically been non-operative. However, for recurrent patellar instability, debate exists for the ideal surgical procedure, generally consisting of MPFL reconstruction plus or minus a number of a la carte procedures. Overall outcomes have not been well-established. JUPITER, or Justifying Patellar Instability Treatment by Early Results, is a hypothesis-driven, multi-center, multi-armed, prospective cohort study that was developed to obtain sufficient subjects to better describe clinical characteristics and predictors of clinical outcomes in the young patellar instability population. In 2018, this multi-center study began recruiting patients and allocated them into first-time patellar dislocation groups and recurrent patellar instability groups. Physician-dependent allocation placed patients into the non-operative group and the operative group, which consisted of either isolated MPFL reconstruction plus or minus a number of a la carte procedures. Follow-up is occurring up to a 10-year period. The purpose of this specific study is to describe the formation of JUPITER and provide objective analysis of patient demographics and patellar instability characteristics at baseline. After training and approval, surgeons began enrolling patients aged 10 to 35 years who had experienced a patellar instability event. We used radiographs, MRI, and clinical assessments to confirm patellar dislocation. We included both patellar subluxations and dislocations, as well as patients with a previous history of patellar instability surgery. We collected baseline information, including patient demographics, dislocation history, physical exam characteristics, and baseline validated patient-reported outcome scores. Patient IQ was the registry platform, and we further divided the cohort into the first-time dislocators and recurrent dislocators and the non-operative and operative treatment groups for comparison. As of December 31st of 2021, 22 surgeons from 12 sites had respectively enrolled a total of 1825 patients for a total of 2,073 needs. 62% of the cohort was female, and the average age is 19.1 years. 14.5% of patients reported a family history of patellar dislocation, most commonly coming from the maternal side. Concerning treatment group allocation, 73% of patients have been allocated to the operative group, and 27% of patients have been allocated to the non-operative group. 63% of all patients reported they had greater than one dislocation. 87% of the recurrent dislocators were indicated for operative treatment, while 47% of the first-time dislocators have been indicated for operative treatment. And of these, 36% were noted to have an osteochondral fracture or loose body, and 24% had a history of contralateral knee instability. Concerning the mechanisms of the injury of the first dislocation, the majority of them have been non-contact, with 68% reporting a non-contact injury. There's no difference between the first-time and recurrent dislocators concerning this, and 29% of patients required a manual reduction on first dislocation. Concerning physical exam characteristics, for the involved knee, J-sign, apprehension, and crepitus were all significantly more positive in the recurrent and operative groups. For the contralateral knee, J-sign and apprehension were significantly more positive, again, in the recurrent and operative groups. Additionally, the recurrent group was nearly twice as likely to be ligamentously lax compared to the first-time patients, defined by a Bain score of five or above. Concerning patient-reported outcome scores, these did vary, but we found for the recurrent dislocators, they generally had lower sporting-related activity scores, and the recurrent patients generally had higher activities of daily living scores compared to the first-time dislocators, suggesting a potential compensatory adaptation mechanism with time. So in conclusion, the Jupiter group has been able to accumulate the largest perspective-collected database for patellar instability to date. Over half, or 63%, of patients in this cohort sustained more than one dislocation. Operative management was indicated in 47% of first-time dislocators versus 87% of recurrent dislocators. Operative management was associated with the presence of osteochondral fractures in our first-time dislocators, as well as a prevalence of instability-related physical exam findings, including J-sign and patellar apprehension. And for patient-reported outcome scores, these varied between our first-time and recurrent dislocators, but do suggest that recurrent dislocators develop compensatory adaptive mechanisms with time. So keep following Jupiter. There will be more to come in the future. Thank you.

JUPITER study

patellar instability

clinical characteristics

young people

patellar dislocation