Overview of Patellofemoral Joint Instability
Top Contributors - Jess Bell, Kim Jackson, Wanda van Niekerk and Ewa Jaraczewska
Introduction[edit | edit source]
Patellofemoral instability is a complex orthopaedic condition that frequently affects children and adolescents.[1][2] It is estimated that the incidence of patellofemoral instability in paediatric patients ranges from 23 to 43 per 100,000 person-years. The highest rates are in teenagers aged between 14 and 18 years.[2]
The management of patellofemoral instability is complex.[3] Vellios et al.[2] note that first-time dislocation may be managed conservatively (i.e. through rehabilitation, bracing, activity modification), but as many as 36 percent of patients will have recurrent instability on the same leg.
Definitions[edit | edit source]
Patellofemoral stability is defined as “constraint by passive soft tissue tethers and chondral/bony geometry that, with muscular forces, guide the patella into the trochlear groove and keep it engaged within the trochlear groove as the knee flexes and extends.” [4]
Conversely, patellofemoral instability is defined as “symptomatic deficiency of the aforementioned passive constraint (patholaxity) such that the patella may escape partially or completely from its asymptomatic position with respect to the femoral trochlea under the influence of displacing force.”[4]
Dislocation - patella comes completely out of the trochlea. Dislocation might be caused by a:[5]
- Trauamatic event (e.g. rugby tackle)
- In these cases, the knee has been structurally intact prior to injury[6]
- These individuals tend to have a better prognosis as there are no underlying structural morphological elements to predispose them to instability
- Minor trauma - a slight tap / knock to the knee causes dislocation
- These individuals tend to have a structural element which predisposes them to instability
Subluxation - a “halfway" point between dislocation and an in situ patella.[5] Patients with a subluxing patella may complain of a painful knee / anterior knee pain.[5][7]
References[edit | edit source]
- ↑ Bailey MEA, Metcalfe A, Hing CB, Eldridge J; BASK Patellofemoral Working Group. Consensus guidelines for management of patellofemoral instability. Knee. 2021;29:305-12.
- ↑ 2.0 2.1 2.2 Vellios EE, Trivellas M, Arshi A, Beck JJ. Recurrent Patellofemoral Instability in the Pediatric Patient: Management and Pitfalls. Curr Rev Musculoskelet Med. 2020;13(1):58-68.
- ↑ Jaquith BP, Parikh SN. Predictors of recurrent patellar instability in children and adolescents after first-time dislocation. J Pediatr Orthop. 2017;37(7):484-90.
- ↑ 4.0 4.1 Post WR, Fithian DC. Patellofemoral instability: a consensus statement from the AOSSM/PFF Patellofemoral Instability Workshop. Orthop J Sports Med. 2018;6(1):2325967117750352.
- ↑ 5.0 5.1 5.2 Robertson C. Patellofemoral Joint Instability Course. Physioplus. 2022.
- ↑ Duthon VB. Acute traumatic patellar dislocation. Orthop Traumatol Surg Res. 2015;101(1 Suppl):S59-67.
- ↑ Monk AP, Doll HA, Gibbons CL, Ostlere S, Beard DJ, Gill HS, Murray DW. The patho-anatomy of patellofemoral subluxation. J Bone Joint Surg Br. 2011;93(10):1341-7.
