Systematic review of the etiology behind patellar clunk syndrome

Table 1 Etiologies associated with development of patellar clunk syndrome: Comparison of published studies^a

Ref.	Postope-rative Knee Flexion (degrees)	Prothes-es Design	Joint Line Level	Patellar Height	Insall- Salvati Ratio	Position of Tibial Tray	Patellar thickne-ss	Patellar tendon length	Femoral condyle offset	Patellar tilt	Posterior tibial slope	Resurfac-ing
Beight et al[40]	Not significant	N/A	Significant	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Anderson et al[22]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	Significant	N/A	N/A
Pollock et al[20]	N/A	Significant	Not significant	Not significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Maloney et al[27]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Yau et al[15]	N/A	N/A	Not significant	Significant	Significant	Significant	N/A	N/A	N/A	Significant	N/A	N/A
Ip et al[23]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Schroer et al[28]	Significant	Significant	N/A	Not significant	Not significant	N/A	N/A	N/A	N/A	Not significant	Not significant	N/A
Fukunaga et al[14]	Significant	Significant	N/A	Not significant	Not significant	Not significant	N/A	N/A	N/A	Significant	N/A	N/A
Dennis et al[5]	Not significant	N/A	Not significant	Significant	Significant	Significant	N/A	Significant	Significant	Not significant	Not significant	N/A
Frye et al[4]	Significant	Significant	Not significant	Not significant	Not significant	N/A	N/A	N/A	N/A	Significant	N/A	N/A
Choi et al[8]	Not significant	Significant	Not significant	N/A	Not significant	N/A	Not significant	N/A	Not significant	Not significant	Not significant	Significant
Costanzo et al[1]	N/A	N/A	N/A	Not significant	N/A	N/A	Significant	N/A	Significant	N/A	N/A	N/A
Gholson et al[32]	Not significant	N/A	Not significant	Not significant	Not significant	Not significant	Not significant	Not significant	Not significant	Not significant	Significant	N/A
Peralta-Molero et al[29]	Significant	N/A	Not significant	Not significant	Not significant	Not significant	Not significant	N/A	N/A	Not significant	Not significant	N/A
Bae et al[41]	N/A	Significant	Not significant	N/A	Not significant	N/A	N/A	N/A	N/A	Significant	N/A	N/A
Toomey et al[42]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Martin et al[19]	Significant	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Snir et al[43]	N/A	Significant	N/A	N/A	N/a	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Tang et al[21]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/a	N/A	N/A	N/A
Rajshekha-r et al[44]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/a	N/A	N/A
Figgie et al[9]	N/A	N/A	Significant	Significant	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A
Ip et al[45]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Lonner et al[17]	N/A	Significant	Not significant	N/A	Not significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Shoji et al[25]	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	Not significant
Ogawa et al[34]	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	Significant	N/A	Significant
Hamilton et al[31]	N/A	N/A	N/A	N/A	N/A	N/A	Significant	N/A	N/A	N/A	N/A	N/A
Martin et al[19]	Significant	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Agarwala et al[2]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Shilling-ton et al[33]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	Significant
McNabb et al[46]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Clarke et al[18]	N/A	Significant	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Ranawat et al[26]	N/A	Significant	N/A	Not significant	Not significant	N/A	Not significant	N/A	N/A	N/A	N/A	N/A
Aglietti et al[16]	Not significant	Significant	N/A	Not significant	N/A	N/A	N/A	N/A	N/A	Not significant	N/A	Significant

^aP = 0.05 for significance. N/A: Not available.

Table 2 Table 1 metrics defined

Postoperative knee flexion	After surgery, the degree to which the knee can flex
Prosthesis design	Several prosthesis designs can be implanted in a TKA
Joint line height	Shortest distance between the fibular head and lateral femoral condyle on AP radiograph
Patellar height	Measured as the perpendicular distance from the inferior pole of the patellar implant to the joint line of the prosthesis
Insall-Salvati ratio	Ratio of the length of the patellar tendon to the length of the patella
Position of tibial tray	Measured as the perpendicular distance of the tibial tray from the patellar tendon
Patella thickness	The width of the patella (medial to lateral)
Patellar tendon length	Length of the patellar tendon superior to inferior
Posterior tibial slope	The degree to which the tibia is lateral to the perpendicular line drawn from the prosthesis
Patellar tilt	Angle subtended by the equatorial line of the patella and the line connecting the anterior limits of the femoral condyles
Femoral condyle offset	Distance between the lateral condyle and the vertical line parallel to the lateral edge of the femur

Table 3 ROBIS Tool for assessing risk of bias in systematic review

	Study eligibility criteria	Identification and selection of studies	Data collection and study appraisal	Synthesis findings	Risk of bias in the review
PCS etiology	Yes	Yes	Yes	Yes	A. Yes
Systematic review					B. Yes
					C. No
					Overall: Low

PCS: Patellar clunk syndrome.