Iatrogenic Patella Baja Following Primary Total Knee Arthroplasty: Is the Patellar Tendon to Blame?

Patellar tendon shortening (PTS) following primary total knee arthroplasty (TKA) is thought to occur because of excessive soft tissue tensioning during wound closure. Few studies have examined the incidence of acute PTS in TKA patients. The purpose of this prospective study was to evaluate the incidence and clinical implications of acute PTS after primary TKA. All patients undergoing primary TKA for osteoarthritis (OA) from January 2024 through April 2024 by a single, fellowship-trained surgeon were included. Patient demographics and range of motion (ROM) were recorded preoperatively. Range of motion and physical therapy (PT) requirements were recorded at 6-week follow-up. Patellar tendon length was determined by the Insall-Salvati ratio (ISR) and measured preoperatively, on postoperative day (POD) 0, and at 6 weeks following surgery. Significant PTS was defined as a decrease in the ISR of ≥10%. In total, 89 patients were included in the analysis. Of these, 54 (60.7%) patients experienced significant PTS and 35 (39.3%) did not experience significant PTS immediately following TKA. Preoperative ISR and ROM was similar between cohorts; however, on POD 0, the ISR decreased by 21.9 ± 8.7% in the significant PTS cohort versus 0.8 ± 10.9% (p < 0.001) in the insignificant PTS cohort. From POD 0 to 6 weeks postoperatively, ISR increased by 25.0 ± 15.8% in the significant PTS cohort versus 7.6 ± 12.0% in the insignificant PTS cohort (p < 0.001). The ISR decreased by 2.9 ± 10.9% for patients in the significant PTS cohort and increased by 5.7 ± 7.9% for patients in the insignificant PTS cohort (p < 0.001). There was no significant difference in PT requirements or ROM between cohorts at 6-week follow-up. Patellar tendon shortening following TKA resolved by 6 weeks postoperatively; no ROM deficits or additional PT requirements were found to exist between cohorts.