Table 3.

Findings of studies looking at the function of the MPFL.

Study	Knee Positions	Quadriceps Tension	MPFL Findings
Conlan et al.19	Full extension	No	MPFL provides 53% of medial restraint Restraining force with all structures intact was 225 N/cm
Hautmaa et al.25	Tests performed with knee at 30° (±5°)	Yes - 2-pound weight applied as resting physiological load	MPFL responsible for 50% of medial restraint with a displacement of 13.8 mm with 5lb of force applied
Farahmand et al.22	Patellar displacement (10 mm) was measured at 0, 10, 20, 30, 45, 60 and 90°	Yes – varying forces used	Decrease in force required to displace patella between 0° and 20° which then remains reasonably constant until 60°
Zaffagnini et al.12	Testing performed at 0, 30, 60 and 90° of flexion	Yes - 60 N isolated force through the quadriceps tendon	With a resected MPFL, there is increased laxity at 30–60° of knee flexion
Desio et al.20	Testing performed at 20° of flexion	Yes – 2lb weight attached to centralise patella	MPFL represents 60% of restraint Average force of 182 N required to achieve maximal patella translation
Senvongse et al.21	Testing performed from 0 to 90°	Yes – 175 N	75 N of force required to displace patella at 20° of knee flexion compared with 126 N and 125 N at 0° and 90° respectively
Mountney et al.24	Knee placed in external rotation	No	Mean tensile strength of 208 N required for MPFL to rupture
Burks et al.23	Secured in 20° of flexion	Yes – 2lb weight attached to centralise patella	Mean tensile strength of 209 N required for MPFL to rupture