*3.2.6 Patellar compression test*

The patella should be palpated for retropatellar tenderness and crepitus which may suggest an injury to the articular cartilage. Compression of the patella during full range of motion of the knee may reproduce the associated pain. The location of the chondral injury may be estimated on the basis of the knee-flexion angle in which pain is experienced. The patellofemoral contact area moves proximally on the patella as the knee flexion increases. Articular lesions on the distal patella are painful during early knee flexion, whereas proximal patellar lesions are manifested with further knee flexion. Clinically suspected chondral lesions should be confirmed by MRI assessment to help in preoperative planning.

#### *Patellofemoral Instability DOI: http://dx.doi.org/10.5772/intechopen.99562*

The flexibility of the lower extremity should be evaluated, especially in reference to hamstrings tightness. Excessive tightness of the hamstrings requires greater quadriceps force for knee extension, leading to increased transmission of contact pressure across the patellofemoral joint. Hamstring flexibility is best assessed by measuring the popliteal angle. Gastrocnemius and soleus tightness should also be evaluated. The flexibility of both muscles can be judged by ankle dorsiflexion with the knee extended. With the knee flexed, the gastrocnemius is relaxed, and the soleus is isolated. In both positions, the ankle should dorsiflex 15 to 20 degrees past neutral. Limitation of ankle dorsiflexion causes a compensatory increase in subtalar pronation, thereby increasing internal tibial rotation during gait [30]. The lower extremity should also be examined for iliotibial band tightness and the examination finding should be compared with that in the opposite limb. Iliotibial band tightness is assessed by performing the time-honored Ober's test [56]. With the patient in the lateral decubitus (with the affected extremity on top), the hip and knees are flexed to 90 degrees initially. The examiner then places one hand on the pelvis to stabilize and monitor for movement. The ipsilateral leg is abducted, brought into full extension at the hip and the knee, and then adducted toward the table. Tightness or pain may be elicited. The test is considered positive if the patient's leg does not lower beyond neutral as the examiner lowers it from an abducted and slightly extended position, suggesting shortness of the tensor fascia lata and iliotibial band. A negative test results in the leg returning normally toward the examination table.
