Patellar Tendinitis: Symptoms, Types, Causes and Treatment

Patellar tendinitis, often called "jumper’s knee," is a common source of pain at the front of the knee, especially among athletes and active individuals. Understanding the symptoms, different types, underlying causes, and the latest treatment options is crucial for both prevention and recovery. This article provides a comprehensive, evidence-based overview of patellar tendinitis, synthesizing the latest research to help you understand and manage this challenging condition.

Symptoms of Patellar Tendinitis

Patellar tendinitis can have a significant impact on daily life, causing discomfort that ranges from mild irritation to severe, activity-limiting pain. Recognizing the symptoms early can lead to more effective management and better outcomes.

Symptom	Description	Triggers/Exacerbation	Source(s)
Pain	Localized pain at the inferior pole of patella	Worse with activity, knee flexion	1, 2, 7
Tenderness	Tenderness to palpation at tendon attachment	Maximal with knee extended	2
Swelling	Mild swelling around tendon	After exercise	3, 7
Functional Loss	Difficulty jumping, running, or squatting	Aggravated by repetitive motion	7

Table 1: Key Symptoms

Pain at the Inferior Pole of the Patella

• The hallmark symptom is pain localized at the lower (inferior) pole of the patella, where the patellar tendon attaches to the kneecap.
• The discomfort often intensifies with activities that load the knee extensor mechanism, such as jumping, running, climbing stairs, or squatting 1, 2, 7.

Tenderness and Swelling

• Physical examination frequently reveals tenderness upon palpating the tendon just below the kneecap, especially when the knee is extended and the quadriceps muscle is relaxed 2.
• Mild swelling may occur around the tendon, particularly following sports or strenuous activity 3, 7.

Functional Limitations

• Individuals with patellar tendinitis commonly report difficulty or pain when performing explosive movements (like jumping) or repetitive knee-bending actions.
• In advanced cases, even walking or standing for extended periods can become painful 7.

Clinical Signs

• Specific clinical tests, such as the "passive flexion-extension sign" and the "standing active quadriceps sign," can help confirm the diagnosis. Tenderness typically decreases when the tendon is under tension, helping to differentiate patellar tendinitis from other causes of anterior knee pain 2.

Types of Patellar Tendinitis

Patellar tendinitis is not a one-size-fits-all diagnosis. Variations in anatomical structure, injury severity, and chronicity can influence how the condition presents and progresses.

Type	Defining Features	Associated Anatomy	Source(s)
Acute	Sudden onset, related to recent overload	Normal anatomy	3, 6
Chronic	Gradual progression, persistent symptoms	Tendon thickening, degeneration	3, 7
Structural Variants	Elongation, ossification, or impingement	Patellar pole/tendon morphology	1, 4
Graded by Severity	MRI-based grading (1-3)	Enthesial region, retinaculum	3

Table 2: Types and Classifications

Acute vs. Chronic Patellar Tendinitis

• Acute patellar tendinitis typically develops following a recent increase in activity or overload. The tendon appears normal on imaging, but symptoms are prominent 3, 6.
• Chronic patellar tendinitis (or tendinosis) evolves over time, often as a result of repeated microtrauma. Chronic cases may show tendon thickening, degeneration, and even partial tears on imaging 3, 7.

Structural and Anatomical Variants

• Some individuals develop unusual anatomical changes, such as elongation or ossification at the inferior pole of the patella, that further complicate the condition 1.
• Anatomical studies reveal that variations in the shape of the inferior patellar pole (pointed, intermediate, blunt) and the attachment site of the tendon (anterior vs. posterior) can predispose to specific types of tendon injury 4.

MRI-Based Classification

• MRI can grade patellar tendinitis severity:
  • Grade 1: Enhancing area adjacent to the patella with possible chondral-bone avulsion.
  • Grade 2: Similar changes without avulsion.
  • Grade 3: Homogeneous, nonenhancing area indicating more extensive degeneration 3.
• Associated findings may include chronic injury to the medial retinaculum 3.

Causes of Patellar Tendinitis

Understanding why patellar tendinitis occurs is essential for both treatment and prevention. Multiple factors—mechanical, anatomical, and biological—may contribute.

Cause	Mechanism	Risk Factors	Source(s)
Chronic Overload	Repetitive loading, microtrauma	Jumping sports, overuse	1, 6, 7
Poor Flexibility	Increased tendon strain due to tight muscles	Tight quadriceps/hamstrings	5
Anatomical Variation	Shape/attachment anomalies in patella or tendon	Pointed/blunt pole, attachment type	4, 6
Rare Local Lesions	Space-occupying masses near the tendon	Osteochondroma, ossification	1, 7

Table 3: Major Causes and Risk Factors

Chronic Overload and Repetitive Microtrauma

• The most common cause is chronic overload—repeated stress from activities that involve frequent jumping, landing, or rapid changes in direction 1, 6, 7.
• This repeated loading leads to microtears, failed healing responses, and eventual tendon degeneration.

Muscular Flexibility

• Poor flexibility of the quadriceps and hamstring muscles significantly increases patellar tendon strain during activity, making tendinitis more likely in athletes with tight muscles 5.
• Preventive strategies often focus on improving muscle flexibility to reduce risk.

Anatomical Predisposition

• The shape of the inferior patellar pole (pointed vs. blunt) and the tendon attachment site can alter the mechanics of the knee, increasing impingement or tensile stress during movement 4, 6.
• For example, a pointed pole with an anterior tendon attachment may cause the patella and tendon to impinge during knee flexion, resulting in localized damage 4.

Rare and Localized Lesions

• Although rare, certain cases are caused by space-occupying lesions such as ossification at the tendon insertion or extraskeletal osteochondromas, which can directly irritate or compress the tendon 1, 7.
• Surgical removal of these lesions can resolve symptoms when present.

Treatment of Patellar Tendinitis

The management of patellar tendinitis is multifaceted, ranging from conservative interventions to advanced surgical techniques. Early and appropriate treatment can greatly influence recovery outcomes.

Treatment	Approach/Intervention	Indication/Outcome	Source(s)
Eccentric Exercise	Slow, controlled lengthening of quadriceps	First-line, improves pain/function	8, 9, 10, 11
Shockwave Therapy	High-energy sound waves to stimulate healing	Adjunct for persistent cases	9, 10, 11
PRP Injections	Platelet-rich plasma to promote repair	Chronic/refractory, long-term benefit	9, 10, 11
Surgery	Open or arthroscopic tendon debridement	Failure after 3-6 months conservative care	1, 11, 12
Other Injections	Steroids, sclerosing agents	Limited/no benefit, not recommended	9, 11

Table 4: Overview of Treatments

Eccentric Exercise

• Eccentric quadriceps training—where the muscle lengthens under tension—is consistently recommended as the first-line treatment.
  • Proven to reduce pain and improve function in both short- and long-term studies 8, 9, 10, 11.
  • Programs typically last 8 weeks or longer, with gradual progression.
• Stretching exercises for the quadriceps and hamstrings are also beneficial, especially for those with poor flexibility 5, 8.
• Pain may limit initial strength gains, so gradual progression is key 8.

Shockwave Therapy and Platelet-Rich Plasma (PRP)

• Shockwave Therapy: Uses sound waves to stimulate tendon healing; effective as a noninvasive adjunct, especially in cases not responding to exercise alone 9, 10, 11.
• PRP Injections: Multiple PRP injections have shown the best long-term outcomes, especially for chronic cases; may accelerate early recovery 9, 10, 11.
  • Single injections may be less effective than a series.

Surgical Options

• Surgery is reserved for patients who fail to improve after 3–6 months of conservative therapy 1, 11, 12.
  • Open Surgery: Involves removing abnormal tissue, drilling the inferior pole of the patella, and sometimes partial tendonectomy. Success rates are high but recovery may take 8–12 months 12.
  • Arthroscopic Surgery: Minimally invasive, includes tendon debridement and excision of abnormal tissue. Associated with a slightly higher success rate and faster return to sport compared to open surgery 12.
  • The choice between open and arthroscopic techniques depends on surgeon expertise and patient preference, as both have demonstrated good outcomes 11, 12.
  • Surgery may also be required for rare structural lesions such as ossification or tumors near the tendon 1, 7.

Other Treatments

• Corticosteroid injections and certain sclerosing agents are not recommended due to limited efficacy and potential adverse effects 9, 11.
• Other experimental approaches include injection of autologous cells or polidocanol, but evidence supporting their use is limited 11.

Rehabilitation and Return to Sport

• Postoperative or post-intervention rehabilitation is critical, focusing on gradual strengthening, flexibility, and safe progression back to activity.
• Return to pre-injury activity levels varies: faster with minimally invasive surgery, but always requires diligent rehab 12.

Conclusion

Patellar tendinitis is a complex condition that requires a tailored, evidence-based approach for optimal management. Here’s a quick summary of the main points:

• Symptoms include localized pain and tenderness just below the kneecap, especially during activity.
• Types range from acute to chronic, with variations in anatomical structure and severity as seen on MRI.
• Causes are multifactorial, involving chronic overload, poor flexibility, anatomical predisposition, and, rarely, local lesions.
• Treatment begins with eccentric exercise and flexibility training, with shockwave therapy and PRP injections for persistent cases. Surgery is effective for refractory tendinitis, with both open and arthroscopic procedures offering good outcomes.

Key Takeaways:

• Early recognition and intervention are crucial for recovery.
• Eccentric exercises and flexibility improvements are cornerstones of care.
• Most patients can avoid surgery, but it remains a successful option when needed.
• Ongoing research continues to refine nonoperative options, especially biologic injections.
• Individualized rehabilitation and a gradual return to sport optimize long-term knee health.

With the right approach, most individuals with patellar tendinitis can look forward to a full return to activity and a pain-free future.