Patellar Tendon-Lateral Trochlear Ridge Distance Is More Specific Than Tibial Tubercle-Trochlear Groove for Patellofemoral Instability
In brief
Patellar tendon-lateral ridge distance at least 4.6 mm identifies instability with 92% specificity
In a matched case-control of 50 knees with recurrent patellofemoral instability and 50 controls, the PT-LTR measurement was highly reliable and, at a cutoff of 4.6 mm, correctly flagged instability in 66% of cases while correctly ruling it out in 92% of non-cases-far higher specificity than the traditional TT-TG metric. The test's moderate sensitivity means it should complement, not replace, existing assessments.
- Journal
- Arthroscopy : the journal of arthroscopic & related surgery : official publication of the Arthroscopy Association of North America and the International Arthroscopy Association (Q1)
- Published
- 13 September 2026
- Study design
- Retrospective cohort
- Evidence level
- Level 3, Low (CEBM 3b)
- Authors
- Adam J Tagliero, Gavin H Ward, Sophia Mavrommatis, Jason Ina, Louis Kang, Rakan Alshaibi, et al.
- PMID
- 42732467
- DOI
- 10.1002/arj.70545
Why clinicians should know about it
- Picked for Anatomy (paper of the day, 14 September 2026): PT-LTR distance, reliable metric for patellofemoral instability
Abstract
PURPOSE: To assess the reliability, predictability, and discriminative capacity of 3 anatomic measurements, tibial tubercle-trochlear groove (TT-TG), tibial tubercle-posterior cruciate ligament, and patellar tendon-lateral trochlear ridge (PT-LTR), where PT-LTR may offer a complementary approach to assessing recurrent patellofemoral instability (PFI) risk. METHODS: Patients diagnosed with PFI before primary patellofemoral stabilization surgery at a single institution between 2022 and 2024 were included. A control group without PFI was propensity matched 1:1 for age, sex, and laterality. Magnetic resonance images were evaluated to measure TT-TG, tibial tubercle-posterior cruciate ligament, and PT-LTR. A priori power analysis determined the cohort size. Statistical analyses compared differences between the PFI and control groups with Student t-tests, receiver operating characteristic analyses, and area under the curve with resultant sensitivity, specificity, and an optimal cutoff. RESULTS: Patients included 50 knees with PFI (28 women, 22 men; mean age 18 ± 5 years). The control group included 50 knees (27 women, 23 men; mean age 18 ± 4 years). Excellent inter- and intra-rater reliability (intraclass correlation coefficient > 0.7) was shown for TT-TG and PT-LTR in the PFI and control groups. The distances for TT-TG, tibial tubercle-posterior cruciate ligament, and PT-LTR were significant predictors (P ≤ .025) of PFI. The average PT-LTR distance difference for the PFI and control groups was 7.0 mm (P < .001). PT-LTR showed an area under the curve of 0.80 and, when ≥4.6 mm, was 66% sensitive and 92% specific for PFI. CONCLUSIONS: The PT-LTR distance is a reliable and discriminative metric for identifying PFI in both pediatric and adult populations. A PT-LTR cutoff value of 4.6 mm showed diagnostic discrimination and substantially high specificity for recurrent PFI, indicating strong ability to identify patients with instability. LEVEL OF EVIDENCE: Level III, retrospective case control study.
Abstract as published, via PubMed.
For healthcare professionals. The summary is generated by AI from the published abstract, and the evidence level is assigned automatically from the study design on the Oxford CEBM hierarchy. Neither is medical advice. Read the full paper before changing practice.