Incidence and Associated Factors of Patellar Clunk Syndrome After Total Knee Arthroplasty: A Retrospective Single-Center Study

Year 2025, Volume: 17 Issue: 3, 252 - 258, 29.10.2025

Yunus Emre Bulum , Erdem Değirmenci

Abstract

Objective: Patellar clunk syndrome (PCS) is an uncommon complication after total knee arthroplasty (TKA), particularly in posterior-stabilized prostheses. It is characterized by a painful catching or “clunk” during knee extension, often caused by fibrous nodule formation at the superior pole of the patella. Reported incidence rates vary widely, and although factors such as implant design, femoral component size, and insert thickness have been proposed, the true incidence and risk factors remain uncertain.
Method: This retrospective study included 330 patients who underwent primary TKA between 2016 and 2018. Demographics, implant design, femoral component size, insert thickness, and radiographic parameters were analyzed. Clinical outcomes were assessed using the Knee Society Score (KSS), and ultrasonographic detection of suprapatellar fibrous nodules was performed.
Results: PCS occurred in 23 patients (7.5%). Incidence was higher in men (12.5% vs. 5.8%, p=0.041), in posterior-stabilized compared with cruciate-retaining prostheses (8.5% vs. 3.1%, p=0.048), and in bilateral versus unilateral procedures (30.4% vs. 5.2%, p<0.001). Smaller femoral components (p<0.001) and thicker inserts (>12 mm, p=0.001) were associated with PCS. No significant differences were found for Insall–Salvati ratio (p=0.914), patellar tendon length (p=0.885), or tibial slope (p=0.891). KSS was slightly lower in PCS patients (p=0.036).
Conclusions: PCS was observed in 7.5% of cases and appeared more frequent with posterior-stabilized prostheses, bilateral TKA, smaller femoral components, and thicker inserts. Radiographic parameters were not predictive. These findings suggest implant and surgical factors may contribute, but results should be interpreted cautiously given the retrospective design.

Keywords

total knee arthroplasty , patellar clunk syndrome , posterior-stabilized prosthesis , femoral component size , polyethylene insert

Total Diz Artroplastisi Sonrası Patellar Clunk Sendromunun Görülme Sıklığı ve İlişkili Faktörler: Retrospektif Tek Merkezli Çalışma

Abstract

Amaç: Patellar clunk sendromu (PCS), total diz artroplastisi (TDA) sonrası, özellikle posterior stabilize protezlerde nadir görülen bir komplikasyondur. Bu sendrom, genellikle patellanın üst tarafında fibröz nodül oluşumu nedeniyle diz ekstansiyonu sırasında ağrılı bir takılma veya “çatırtı” ile karakterizedir. Bildirilen insidans oranları büyük farklılıklar göstermektedir ve implant tasarımı, femoral komponent boyutu ve insert kalınlığı gibi faktörler öne sürülmüş olsa da, gerçek insidans ve risk faktörleri belirsizliğini korumaktadır.
Yöntem: Bu retrospektif çalışmaya, 2016 ile 2018 yılları arasında primer TDA geçiren 330 hasta dahil edilmiştir. Demografik özellikler, implant tasarımı, femoral bileşen boyutu, insert kalınlığı ve radyografik parametreler analiz edildi. Klinik sonuçlar Knee Society Score (KSS) kullanılarak değerlendirildi ve suprapatellar fibröz nodüllerin ultrasonografik tespiti yapıldı.
Bulgular: PCS 23 hastada (%7,5) görüldü. İnsidans erkeklerde (12,5% vs. 5,8%, p=0,041), arka stabilizasyonlu protezlerde çapraz bağ koruyucu protezlere kıyasla (8,5% vs. 3,1%, p=0,048) ve bilateral prosedürlerde unilateral prosedürlere kıyasla (30,4% vs. 5,2%, p<0,001) daha yüksekti. Daha küçük femoral bileşenler (p=0,001) ve daha kalın insertler (>12 mm, p=0,001) PCS ile ilişkiliydi. Insall–Salvati oranı (p=0,914), patellar tendon uzunluğu (p=0,885) veya tibial eğim (p=0,891) açısından anlamlı bir fark bulunmadı. KSS, PCS hastalarında biraz daha düşüktü (p=0,036).
Sonuç: PCS, vakaların %7,5'inde gözlendi ve posterior stabilize protezler, bilateral TKA, daha küçük femoral bileşenler ve daha kalın insertlerde daha sık görüldü. Radyografik parametreler öngörücü değildi. Bu bulgular, implant ve cerrahi faktörlerin katkıda bulunabileceğini düşündürmektedir, ancak sonuçlar retrospektif tasarım göz önüne alındığında dikkatli bir şekilde yorumlanmalıdır.

Keywords

Total Diz Artroplastisi , Patellar Clunk Sendromu , Posterior Stabilize Protez , Femoral Bileşen Boyutu , Polietilen İnsert

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