Summary

Critical elements of the physical examination and radiographic evaluation of patellofemoral instability patients were determined by survey and critically evaluated by experts in patellofemoral disease to obtain a consensus recommendation.

Abstract

Multiple radiographic and physical examination criteria have been described to evaluate patellofemoral patients. Clear and accurate documentation can help in determination of risk factors, natural history, and results of treatment. We worked to identify a common set of evaluation criteria to help standardize evaluation and description for clinicians and researchers.

Materials And Methods

An international 14 member task force selected on the basis of publication and presentation in the area of patellofemoral evaluation and treatment. To provide structure to data gathering and assessment, a modified Ebel procedure for content validation was used. This consists of 3 elements: (1) simple/face validation by experts (2) review and acceptance from an international group of experts (3) face-to-face discussion on items that do not receive 80% agreement. Task force members were surveyed to identify potential critical factors for patellofemoral evaluation. 30 physical examination elements and 20 radiographic findings were identified as possibly important for documentation. Using a web-based survey tool, items were rated using a 5 point Likertscale; with 1 being “potentially useful, but not critical,” to 5 points, “most critical, must always be assessed and recorded.” All members of the task force and the International Patellofemoral Study Group (IPSG) were invited to fill out the survey.

Results

Twenty nine international experts filled out the survey. No item was ranked “5” by all experts. The most highly ranked item was radiographic measurement of patella alta (mean, 4.52). The top items clustered and were separated from the lower ranked items by a minimum of 0.25, indicating that these items were quantitatively different. 12 physical exam (Table 1) and 9 radiographic items (Table 2) had > 4.0.
TABLE 1. Physical examination
Presence of Lateral Apprehension
Whether the obligatory dislocation occurs in flexion or extension
Presence of a J sign
Knee range of motion (passive)
Lower limb alignment
Patella tracking
Generalized laxity: Beighton score or similar
Effusion: presence and severity
Presence of Quadriceps atrophy
Patella mobility: (quadrants or similar method), medial and lateral
Degree of flexion at which tilt and mobility are assessed
Patella tilt / tightness of lateral retinaculum

TABLE 2. Radiographic evaluation
Patella height
Tibial tubercle – trochlear groove (TT-TG) distance
How TT-TG was assessed: CT/MRI
Presence of Patellofemoral joint space narrowing
Skeletal maturity based on visible physes
Degree of knee flexion in which all axial films are obtained
Presence of Patella subluxation or translation on axial imagining
Trochlear dysplasia grade
Location and size of cartilage lesions of the patella or trochlea
Crossing sign: Present/absent

The results were reviewed with Task Force and IPSG members at AOSSM, ISAKOS, and IPSG (>50 experts). There was general agreement on relative importance and the criteria and number of items. The recommendation was to utilize the highest ranked items.

Discussion

Using a validated consensus based methodology, key physical examination and radiographic elements for the evaluation of patellofemoral patients were identified and ranked. These can be used by clinicians and researchers to help better systematically evaluate and treat patellofemoral patients.