Patellar tendonitis, also known as jumper’s knee, is inflammation of the patellar tendon. This tendon connects the patella (kneecap) to the tibia. Its function is to extend the leg by transmitting the force produced by the quad to do so. Tendonitis develops when there is overuse of the tendon, Athletes who participate in sports such as basketball or volleyball are more likely to develop patellar tendonitis. Tendonitis is a complex injury that is difficult to overcome and can delay an athlete’s return to play. Understanding the forces acting on the tendon during jumping can help create a plan that will help the athlete return to play quickly and reduce the chances of reinjury.
A 2010 study, was conducted to determine the differences in the tendon properties between adults and children. An experiment that was done during the study was to measure the length of the tendon before and while there is force acting on the tendon. As shown in Figure 2, it can be seen there is a small elongation of the tendon. This confirms the idea that the tendon acts similarly to a spring which can be stretched but will return to its original state.
Figure 2: Patella Tendon before quadricep contraction (a) and during contraction (b) Håvard Visnes et al
A different study from 2005 was conducted to determine if an athlete that natural genetic advantages for jumping higher and more explosively were also more likely to developing tendonitis. The study used high school student-athletes to take the data from their counter movement jump (CMJ), which determines the force the athlete produces when they jump, and compares that with if the athlete developed jumpers’ knee over the course of their high school athletic career. The study found that in male athletes with high CMJ scores were more likely to develop jumpers’ knee while female athletes did not have any correlation of developing symptoms no matter their CMJ score.
Once patellar tendonitis is diagnosed a recovery plan is important to be created and followed to avoid reinjury or worse outcomes such as a tendon tears or a fracture of the tibia/patella. The most common recovery approach focuses on strengthening the tendon through eccentric loading of both the patellar tendon and the quadriceps.
Eccentric loading is when a force is applied to the muscle, in this case the quad, at its max contraction. For the quad, max contraction occurs when the leg is fully extended. The load would be applied best with a leg extension machine, commonly found in most gyms. The important part of rehabbing a patellar tendon is to gradually increase the workload back to what it was before the injury. Jumping should be part of rehab but not at fully effort initially, starting with eccentric exercises then working the athletes way back up to 100%. Once there is pain free performance after multiple sessions at max effort then the athlete should return to play.
To conclude, patellar tendonitis is an injury that affects athletes in jumping intensive sports such as basketball and volleyball. Individuals affected often times have genes that promote explosive and high jumping. Rehab should be done thoroughly and with a plan to reduce the risk of reinjury and get the athlete to return to play quickly.