OBJECTIVETo study the contribution of medial or lateral stabilizer to the stability of the patella, to explore the function and effect of releasing the LPR clinically and to provide a biomechanical basis for the clinical treatment of patellar instability(PI).

METHODSThe quadriceps femoris of 6 fresh human cadaver knees were loaded to simulate a normal condition of muscle strength. First the loading force was measured and recorded, which subluxated the patella with the different degrees of knee flexion. Intervention 1:released the medial patellar retinaculum(MPR) to simulate pathologic conditions, then repeated the above manipulates and recorded the loading force. Intervention 2:released the LPR furthermore to simulate clinical surgical treatment, then repeated the above manipulates and recorded the loading force.

RESULTSAfter releasing the MPR, the loading force which subluxated the patella were decreased obviously, and there were significant differences between the two groups(<0.05). The above loading force was further decreased after the further release of LPR, but the difference was not significant(>0.05).

CONCLUSIONSMPR plays an important role in maintaining the stability of the patella and in the normal trajectory of the patellofemoral joint. The attention should be paid to the repair or reconstruction of the MPR in the treatment for patella recurrent lateral dislocation subluxation. Releasing the LPR is not a best choice.