Relationship between patellar tendon length and surgical treatment for patellar tendinosis

The incidence of athletic injuries in the adolescent population seems to be on the rise. In the United States, Merkel et al. report 3.5 million youth under the age of 15 years old received medical care each year for injuries that occurred during sports.1 The higher incidence of injury can be attributed to an increase in sports specialization, an increase in practice lengths and higher intensity at younger age. In addition, many young athletes today work with personal trainers to improve overall performance in their chosen sport. These increased demands on individuals who are still growing may be contributing to the rise in tendonitis problems in this age group. To further investigate reasons for patellar tendonitis, our staff looked at the relationship of those with patella alta (longer than normal tendon length) and patellar tendinosis.


Patellar tendinitis (jumper’s knee) is an overuse injury (inflammatory issue) of the patellar tendon. The symptoms include pain below the patella (kneecap) when running, sprinting, pushing off and jumping. There is typically tenderness present where the tendon attaches on the bottom of the patella. Patellar tendinitis tends to feel better when at rest or not performing running and jumping type activities.

Patellar tendinosis, or recalcitrant patellar tendinosis (RPT), is the adaptive process where the body can no longer heal itself and histologically, there are parts of the tendon that becomes necrotic, or dead, When patellar tendonitis progresses to this point, the tissue will not heal on its own.

Generally, patellar tendinitis can be treated with proper rehab. However, if tendonitis is not properly diagnosed and treated early then it progresses to recalcitrant tendinosis where surgical intervention becomes the primary treatment recommendation.

Our staff looked at a group of 45 patients who were scheduled for surgery due to recalcitrant patellar tendinitis. As a control group, we also looked at 45 patients who were scheduled for anterior cruciate ligament reconstruction (ACLR) and did not have any previous patellar tendinosis. The patellar tendons were measured in both groups preoperatively on a lateral radiograph with the knee in 60 degrees of flexion. Measurements were taken from the distal aspect of the inferior pole of the patella to the insertion site on the tibial tubercle. We also looked at variables, such as primary sports played and preoperative quadriceps strength of the noninvolved leg isokinetically, and normalized them to body weight. The RPT group was matched to the ACLR group based on sex, height and weight.

The patients with RPT had statistically significant longer patellar tendon lengths at 57.6 mm compared to the ACLR group at 46.1 mm, p-value < .001. The most frequent sports played in RPT was basketball at 38% and volleyball at 22%. The most common sport played for the ACLR group was basketball at 22% and football at 20%. When the jumping sports of basketball and volleyball were combined, the RPT group showed a statistically significantly higher distribution of patients playing these sports compared to the ACLR group (60% vs 31%), p-value of .006. The preoperative isokinetic quadriceps strength failed to show a statistically significant difference.

Patients scheduled for surgery for RPT had longer patellar tendons compared to those without a history of patellar tendinosis and are more likely to play jumping sports. This is clinically significant to better evaluate, diagnose and educate individuals with longer than normal patellar tendons who develop tendinitis, especially for those playing basketball and volleyball. When patellar tendonitis is recognized and diagnosed, especially for those with longer than normal patellar tendons, it is advised to treat early, manage workloads, and educate on symptom management to avoid progression that can lead to surgery.

This study has been accepted to the American Physical Therapy Association Combined Sections Meeting in 2023 as a poster presentation and to the American Orthopedic Society of Sports Medicine 2023 Meeting as a poster presentation.


  1. Merkel D.L. Youth Sport: Positive and Negative Impact on Young Athletes. Open Access J. Sports Med. 2013; 4:151-160, doi:10. 2147/OAJSM. S33556.