The kneecap (patella) has some important functions. One is to move up and down over the knee joint during motion. This is called patellar tracking. If the ligament along the outside edge of the patella is too tight, the kneecap gets off center. This can cause painful problems.
This tracking mechanism can get uneven when a knee joint is replaced. The procedure to replace the knee joint is called total knee arthroplasty (TKA). Doctors must be very careful when using a tourniquet during this operation. It has been shown that the pressure from the tourniquet can put a strain on the patellar ligament.
Likewise, the tourniquet can put tension on the quadriceps (thigh) muscle where it attaches to the patella. Too much pressure can be a problem. When the tourniquet is released, the patella may pull too far to the side, affecting patellar tracking.
In this study, researchers looked at the stress on patellar tracking during TKA. Two different ways to perform the operation were compared. In one method, the incision is made alongside the kneecap (through the patellar ligament). This is called the parapatellar approach.
In the other method, the opening to the knee is made above the kneecap (through the quadriceps muscle). This method is called the midvastus approach. When the tourniquet was taken off after this surgery, stress in the outer portion of the knee went down. The authors conclude that patellar tracking must be rechecked after deflation of the tourniquet when a midvastus incision is made for TKA.
Stress on the patellar ligament was much less after the parapatellar approach. This was true for all angles of knee flexion. The authors emphasize that tracking of the kneecap should be rechecked after releasing the tourniquet, regardless of the surgical method used.