Abstract
Introduction Chronic patellar dislocation (CPD) associated with osteoarthritis is a rare and challenging
problem, especially in patients with Down syndrome (DS). Chronic alteration of patellofemoral
(PF) function due to severe malalignment leads to progressive joint destruction, potentially
resulting in tricompartmental osteoarthritis. Various techniques have been described
for its resolution, ranging from soft tissue procedures to total knee arthroplasty
(TKA).
Case presentation A 29-year-old male with DS presented with a one-year history of atraumatic right
knee pain, associated with episodes of joint effusion. Initially, he was diagnosed
with septic arthritis. Physical examination showed hyperlaxity (Beighton score 8),
limping gait, CPD, irreducible genu valgum, and tricompartmental osteoarthritis with
13.3° genu valgum on the right side. Treatment included TKA and extensor mechanism
realignment through lateral retinaculum lengthening and advancement of the vastus
medialis obliquus (VMO) using the Insall technique. At 8 months postoperatively, the
patient was pain-free, had no new episodes of patellar dislocation, and was independent
in basic activities of daily living.
Discussion This is a complex case of gonarthrosis, and patellar instability associated with
genu valgum in a patient with DS and hyperlaxity. Along with CPD, we faced a 13.3°
valgus deformity and tricompartmental osteoarthritis. A primary posterior-stabilized
(PS) TKA was planned with the option for increased constraint intraoperatively, along
with soft tissue realignment. The literature demonstrates that this step is essential
to restore PF biomechanics and achieve good functionality.
Keywords
chronic patellar dislocation - total knee replacement - lateral retinacular release
- down syndrome
