RADIOGRAPHIC EVIDENCE OF ABNORMAL A/P PATELLAR TILT IN PATIENTS WITH PATELLAR TENDONITIS.

Tyler TF, Hershman EB, Nicholas SJ, Berg J, Gleim GW, McHugh MP

Nicholas Institute of Sports Medicine and Athletic Trauma, New York, NY

PURPOSE: Abnormal patellofemoral position has been identified as a contributing factor in several patellofemoral pathologies. Patellar tendonitis is an overuse injury attributed to excessive stress on the patellar tendon. The role of imaging studies in identifying patellar tendonitis remains controversial. The purpose of this study was to determine if patellar tendonitis was associated with abnormal patellofemoral position in the sagittal plane. A new radiographic measurement called the A/P patellar tilt angle was defined as the angle created by a line drawn along the anterior cortex of the distal femoral diaphysis and a line drawn along the central longitudinal ridge of the articular surface of the patella.

METHODS: Optimum radiographic position was determined using five cadaveric knees. Normative values and measurement reliability were established using 58 individuals with no history of knee pathology.

SUBJECTS: Lateral radiographs were obtained on 77 patients (95 knees) with symptomatic anterior knee pain who met our inclusion criteria for one of 3 isolated pathologies of the patellofemoral joint: patellar tendonitis (19), patellofemoral pain syndrome (PFP) (42), or patients more than six months following bone-patellar tendon-bone autograft ACL reconstruction (16). All measurements were made by a single, blinded investigator.

ANALYSIS: Reliability was assessed by Pearson product-moment correlation coefficients. A/P tilt patellar angles were compared using T-tests.

RESULTS: Intratester measurements on normals exhibited high reliability (ICC=.97). The A/P tilt patellar angle for the patellar tendonitis group was 25.6° +/-7.0° which was significantly lower (p<0.01) than the normal population (30.8+/-6.7). The mean A/P tilt angle for the PFP group (29.1° +/-8.5°) and the ACL reconstruction patients (35.5°+/-6.2) was not different from the control population (p=0.29 and p=0.19).

CONCLUIONS: Our study demonstrates that patients with patellar tendonitis have abnormal patellar position in the sagittal plane. In this group of patients the inferior pole of the patella was tilted anteriorly, away from the tibial tubercle.

RELEVANCE: This difference in A/P tilt angle compared to controls may represent increased tension through the extensor mechanism resulting in enthesopathy.

Journal of Orthopaedic and Sports Physical Therapy, 31: A-48, PL12, 2001.