Patellar Tendonitis History and Epidemiology

Patellar tendonitis presents with a history of activity-related anterior knee pain. Symptoms initially appear after sports activity, particularly sports involving jumping. Repetitive loading over a single session or with insufficient rest between sessions leads to tears and altered mechanics of the tendon.¹ Individuals will report highly localized pain and indicate the areas of the distal patellar pole and proximal patellar tendon. Generally, there is no precipitating incident, and pain develops gradually. As the condition progresses, pain can be brought on by any activity, or it can become continuous.²

Patellar tendonitis is also known as jumper’s knee or patellar tendinopathy. It occurs primarily in sports involving repetitive loading of the patellar tendon (eg, basketball, volleyball, athletic jump events, tennis, and football).¹Due to frequent under-reporting of sports injuries, incidence data is imprecise. Incidence is extremely high in elite athletes, with a prevalence of 32% in basketball players and 44.6% in volleyball players (vs 14.4% for recreational volleyball players). Amateur athletes have an overall prevalence of 8.5%.²Patellar tendonitis predominantly occurs in males. A study on adolescent basketball players reported an incidence of 11% in males and 2% in females.³ The individuals most impacted are adolescents to those in their mid-30s.⁴

Diagnostic Workup

Diagnosis mainly relies on thorough patient history and physical examination. Detailed information regarding sport, position played, level of performance, and practice and competition schedule should be obtained. A thorough examination of the entire lower extremity should be performed to identify potential contributing hip, knee, ankle, or foot issues.

Risk factors include a high BMI, large abdominal circumference, limb-length discrepancy, and flatfoot arch.² The condition is also associated with weak quadriceps and low quadricep and hamstring flexibility.

Knee anatomy risk factors include abnormal patellar height, previous ongoing inflammation of the knee, and excessive force generation on the knee. Ligamentous laxity, quadriceps and hamstring tightness, and excessive Q-angle of the knee are also risk factors.⁴

Functional limitation and symptom classifications include:

Blazina Pain Staging

Stage 1: Pain following sports activity
Stage 2: Pain at start of sports activity, resolves with warmup, may reappear upon fatigue
Stage 3: Pain while at rest and while active, affects sports performance
Stage 4: Tendon rupture⁵

Acuity Staging

Acute: symptoms present up to 6 weeks.
Sub-acute: symptoms present for 6 to 12 weeks.
Chronic: symptoms persist for more than 3 months.

Patellar Tendonitis Physical Examination

Examination should include the entire lower extremity to identify related findings in the hip, knee, foot, or ankle.

Typical findings at the knee include:

Localized swelling overlying the patellar tendon with tenderness on palpation
Basset’s sign: positive if marked reduction in tenderness to palpation is elicited in the flexed knee position
Standing active quadriceps sign: positive if marked reduction in tenderness to palpation is elicited whilst the quadriceps muscle is contracted⁴

Imaging is not considered diagnostic, as most studies have found no correlation between imaging findings and disease severity.

Recommended imaging techniques include:

X-ray: AP, Lateral, and skyline views taken to exclude bone pathology. May show tendinous changes such as calcification, elongation of patella, and inferior traction spur.
MRI: (78% sensitivity, 86% specificity) with typical findings of increased signal in the posterior proximal tendon and tendon thickening. Can delineate intra-articular pathology, allowing inclusion of multiple conditions for differential diagnosis, whereas ultrasound cannot.
Ultrasonography: (sensitivity 58%, specificity 94%) may be used to locate intratendinous lesions, typically in the posterior portion of the tendon adjacent to the inferior pole. Also, tendon thickening, irregularity of the paratenon, intratendinous calcifications, and erosions of the inferior pole of the patella should be checked. Use ultrasonography when MRI is not an option.

Differential Diagnosis

Patellar tendonitis signs and symptoms may overlap with other knee conditions, including pain with prolonged sitting, squatting, and stair climbing, or prolonged knee flexion, aka “movie theater” sign.

Differential diagnostic considerations include:^2,4

Patellofemoral pain syndrome
Fat-pad syndrome
Meniscal tears
Cartilage lesions
Referred pain
Osgood-Schlatter disease
Quadriceps injury
Bursitis of the superficial and deep infrapatellar bursae
Osteochondritis dissecans
Patellar subluxation
Chondromalacia
Patellar tracking problem

Patellar Tendonitis Management

Evidence-based therapies are lacking for this condition, which is often refractory to treatment. As a result, numerous alternative and experimental treatments are often utilized.⁴

Non-Surgical

Rest without immobilization to avoid muscle and tendon atrophy
Taping or infrapatellar straps
Weight reduction to reduce tendon strain
Eccentric exercise has been shown to be as effective as surgical treatment.⁴Recommended as first-line therapy, particularly in the early stages. Promotes collagen remodeling in the patellar tendon, thereby making the tendon more resilient to exercise-related stress. Exercises should be performed using a decline board and to a level of discomfort. Use a 12-week course before considering surgery.

Experimental or Investigational Therapies

Extracorporeal Shock Wave Therapy – based on pain reduction through hyperstimulation, causing reduction of ascending pain transmission; stimulation of tissue regeneration by mechanical load; and breaking up of tendon calcification. It has demonstrated mixed results, with significant pain reduction and functional improvement compared to physical therapy and NSAIDs in one randomized trial,² though a 2021 meta-analysis found no advantage.⁶
Platelet-rich plasma – provides growth factors thought to speed healing.
Stem cell therapy – thought to improve tissue healing and remodeling.
Hyaluronic acid – has been shown to reduce inflammation and speed tendon healing in early trials.
Sclerosing agents – used to inhibit neovascularization, which occurs in 60 to 80% of patients with pain.
Dry-needling – a form of trigger point therapy.
Aprotinin injection – inhibits matrix metalloproteinases.
Hyperthermia – a combination of deep heating and superficial cooling to promote pain relief and tissue repair.

Patellar Tendonitis Surgical Options

Required in 10% of patients; indicated in partial tendon tear and pain stage 3. Patellar tendon repair protocol options include:²

Open Surgery – An 87% success rate has been reported; 8.3 months return to sport. Incision is made through the anterior patellar tendon to access and debride the posterior tendon. Distal 5 mm of the patella are resected, and the inferior pole is perforated to stimulate repair.²
Arthroscopic Surgery – A 91% success rate has been reported; 3.9 months return to sport. Synovial tissue adjacent to the inferior patellar pole is resected to expose degenerative tissue, which is resected. Distal 5 mm of the patella are resected.²

Post-surgical rehabilitation is the same for both: immediate full weight bearing with free range of motion to tolerance. Pain management, eccentric squat exercises on an inclined board, and strength training start 10 days post-op.

References

Malliaras P, Cook J, Purdam C., et al. Patellar Tendinopathy: Clinical Diagnosis, Load Management, and Advice for Challenging Case Presentations. J Orthop Sports Phys Ther. 2015 Nov;45(11):887-98. Published online September 21, 2015. doi:10.2519/jospt.2015.5987
Figueroa D, Figueroa F, Calvo R. Patellar Tendinopathy: Diagnosis and Treatment. J Am Acad Orthop Surg. 24(12):e184-e192. doi:10.5435/JAAOS-D-15-00703
Cook JL, Khan KM, Kiss ZS, et al. Patellar tendinopathy in junior basketball players: a controlled clinical and ultrasonographic study of 268 patellar tendons in players aged 14-18 years. Scand J Med Sci Sports. 10(4):216-20. doi:10.1034/j.1600-0838.2000.010004216.x
Santana JA, Mabrouk A, Sherman AI. Jumpers Knee. National Library of Medicine: StatPearls. Last updated July 19, 2022.
Rosso F, Bonasia DE, Cottino U, et al. Patellar tendon: From tendinopathy to rupture. Asia Pac J Sports Med Arthrosc Rehabil Technol. 2(4):99-107. Published online October 2015. doi:10.1016/j.asmart.2015.07.001
Challoumas D, Pedret C, Biddle M, et al. Management of patellar tendinopathy: a systematic review and network meta-analysis of randomised studies. BMJ Open Sport Exerc Med. 7(4):e001110. Published online November 2021. doi:10.1136/bmjsem-2021-001110

Author Bio

Tracey Roizman, DC, is a chiropractor and medical writer.