PATELLAR TENDINITIS (JUMPER'S KNEE)
Proximal tendon angiofibroblastic hyperplasia | Eccentric loading key | Contraindication to steroids | VISA-P score
BLAZINA CLASSIFICATION
Critical Must-Knows
- Pathology is degenerative, not inflammatory (tendinosis vs tendinitis)
- Inferior pole of patella is classic site of tenderness (Bassett's sign)
- Eccentric strengthening on decline board is gold standard rehab
- Steroid injections are contraindicated due to rupture risk
- Surgical debridement indicated after 6 months of failed conservative care
Examiner's Pearls
- "Tenderness is typically at the proximal posterior patellar tendon (inferior pole)
- "Pain induced by extension against resistance
- "Bassett's sign: tenderness palpated in full extension disappears in flexion
- "Ultrasound shows hypoechoic area and neovascularization
Critical Exam Points for Jumper's Knee
Terminology Matters
It is a tendinopathy/tendinosis, NOT an acute inflammatory "tendinitis". Histology shows angiofibroblastic hyperplasia, mucoid degeneration, and absence of inflammatory cells. Use "tendinopathy" in the exam.
Steroid Contraindication
NEVER inject corticosteroids into the patellar tendon. It causes collagen necrosis and significantly increases the risk of acute tendon rupture. This is an immediate fail point in vivas.
Bassett's Sign
Bassett's sign distinguishes patellar tendinitis from other anterior knee pain. Localization of tenderness at distal pole of patella in full extension, which disappears in 90 degrees flexion (tendon tension prevents deep palpation).
Differential Diagnosis
Rule out Sinding-Larsen-Johansson (apophysitis) in adolescents, patellofemoral pain syndrome, and Hoffa's fat pad impingement. Location and patient age are key discriminators.
Quick Decision Guide - Anterior Knee Pain
| Condition | Location | Key Feature | Management |
|---|---|---|---|
| Patellar Tendinopathy | Inferior pole patella | Pain with jumping/eccentric load | Eccentric rehab |
| Patellofemoral Pain | Retropatellar/diffuse | Pain with stairs/sitting (movie sign) | VMO strength, tracking |
| Osgood-Schlatter | Tibial tubercle | Adolescent, prominent tubercle | Rest, self-limiting |
| Sinding-Larsen-Johansson | Inferior pole patella | Adolescent apophysitis | Rest, self-limiting |
| Hoffa's Fat Pad | Infrapatellar medial/lateral | Pain with full extension (impingement) | Extension block taping |
Tendinosis Pathology - MAD
Memory Hook:The tendon is MAD, not inflamed
Rehab Principles - EEE
Memory Hook:EEE for Excellent tendon remodeling
Surgical Indications - 6-FAIL
Memory Hook:Surgery only after 6 months of FAILure
Overview and Epidemiology
Patellar tendinopathy, commonly known as Jumper's Knee, is an overuse injury describing pain at the inferior pole of the patella. It is characterized by focal degeneration of the proximal patellar tendon.
Epidemiology:
- Prevalence: High in jumping sports (volleyball 40%, basketball 30%)
- Age: Typically 15-30 years old
- Gender: Male greater than Female (2:1)
- Risk Factors:
- Extrinsic: Hard playing surfaces, increased training volume
- Intrinsic: Poor quadriceps flexibility, vertical jump height (higher jumpers at higher risk), ankle dorsiflexion stiffness
The Jumper's Paradox
Ironically, better athletes are more prone to this condition. Higher vertical jump ability correlates with increased load on the extensor mechanism during landing (eccentric phase), leading to higher injury risk.
Pathophysiology and Mechanisms
Anatomy:
- Patellar Tendon: Connects patella to tibial tubercle
- Inferior Pole: Most common site of pathology (proximal posterior aspect of tendon)
- Vascularity: Posterior proximal insertion is a relatively hypovascular zone ("watershed area")
Pathophysiology (Tendinosis vs Tendinitis):
- Historically termed "tendinitis" implying inflammation
- Current understanding: Degenerative process (Tendinosis)
- Histology:
- Angiofibroblastic hyperplasia: Neovascularization with nerve ingrowth (pain source)
- Mucoid degeneration: Increased ground substance
- Collagen disorganization: Loss of parallel type I collagen bundles
- Absence of inflammatory cells: No neutrophils or macrophages
Why is it painful?
If inflammation is absent, why does it hurt? Pain is driven by neovascularization accompanying neoinnervation (sensory nerve ingrowth) into the degenerative area. Sclerosing therapy targets these neovessels.
Classification Systems
Blazina Classification (Clinical)
Used to grade severity and guide treatment.
| Stage | Symptoms | Function | Treatment |
|---|---|---|---|
| Phase 1 | Pain only after activity | No functional impairment | Ice, NSAIDs, eccentric rehab |
| Phase 2 | Pain during and after activity | Can still compete/perform | Activity mod + intense rehab |
| Phase 3 | Pain during and after | Unable to compete at level | Prolonged rest, consider surgery |
| Phase 4 | Complete tendon rupture | Loss of extension | Surgical repair |
Blazina Transition
Progression from Phase 2 to Phase 3 is the critical tipping point. Once performance is affected (Phase 3), surgical consideration becomes more relevant if rehab fails.
Blazina staging is the most commonly used system in clinical practice.
Clinical Presentation and Assessment
History:
- Anterior knee pain localized to inferior patellar pole
- Aggravated by jumping, landing, deceleration (eccentric load)
- "Movie sign" (pain with prolonged sitting) - can overlap with PFPS
- History of recent increase in training volume
Physical Examination:
Physical Exam Findings
| Manoeuvre | Finding | Significance |
|---|---|---|
| Palpation | Tenderness at inferior pole of patella | Classic site (proximal insertion) |
| Bassett's Sign | Tenderness in extension, disappears in flexion | Differentiates from diffuse PFPS |
| Decline Squat Test | Pain on single-leg decline squat | Loading test for tendinopathy |
| Quad Atrophy | VMO wasting | Chronic inhibition |
| Hamstring/Quad tightness | Reduced flexibility | Predisposing factor |
Bassett's Sign Explained:
- Extension: Patterns tendon is lax; inferior pole palpation is possible.
- Flexion (90 deg): Tendon tightens ("trampoline"); deep palpation of the posterior aspect of the proximal tendon is impalpable.
- Positive sign = Tenderness present in extension, absent in flexion.
Check Hip and Ankle
Always examine the hip (restriction, FAI) and ankle (dorsiflexion restriction). Stiffness above or below forces the knee to absorb more kinetic energy during landing, overloading the tendon.
Investigations
1. Radiographs (X-ray):
- Usually normal
- May show:
- Elongated inferior patellar pole (impingement theory)
- Intratendinous calcification (chronic)
- Osgood-Schlatter or Sinding-Larsen-Johansson sequelae
2. Ultrasound (US):
- First-line imaging modality
- Findings:
- Tendon thickening
- Hypoechoic area (focal degeneration)
- Doppler flow (neovascularization) - correlates with pain
- Advantages: Dynamic, cheap, bilateral comparison
3. MRI:
- High sensitivity (95%)
- Findings: Increased signal intensity on T2/STIR in proximal posterior tendon
- Useful to rule out other pathology (meniscus, cartilage, bone edema)
- Note: MRI signal abnormalities can be present in asymptomatic athletes ("imaging-clinical mismatch"). Treat the patient, not the scan.
Imaging Modality Comparison
| Modality | Pros | Cons |
|---|---|---|
| Ultrasound | Dynamic, shows neovascularization, cheap | Operator dependent |
| MRI | Anatomy definition, rules out other pathology | Expensive, static, high false positive rate |
| X-ray | Rules out bony pathology | Misses soft tissue pathology |
Management
Initial Management (Phase 1-2):
- Relative Rest: Avoid aggravating activities (jumping)
- Ice: For symptom control
- NSAIDs: Short course for analgesia (not healing)
- Biomechanical correction: Orthotics, technique modification
Rehabilitation Protocol (Gold Standard):
- Isometric loading: (e.g., Spanish squat hold) - analgesia effect
- Isotonic loading: Slow heavy resistance
- Eccentric loading: Decline board squats
- Functional/Plyometric: Return to sport progression
Eccentric Strengthening (Decline Board):
- Decline board (25 degrees) isolates patellar tendon (removes calf contribution)
- Perform single-leg squats
- "Pain allowed" protocol (mild pain acceptable during exercise)
- 3 sets x 15 reps, twice daily, 12 weeks minimum
Decline Board Mechanism
The decline board increases load on the patellar tendon by 25-30% compared to flat ground squats by maximizing knee flexion moment while minimizing hip flexion and ankle dorsiflexion contribution.
Adherence to the eccentric program is the single most important factor in conservative success.
Surgical Technique
Arthroscopic Patellar Tenotomy/Debridement:
Setup:
- Supine, tourniquet, standard portals (AL, AM)
- Knee flexed 90 degrees
Steps:
- Diagnostic scope: Rule out other pathology (plica, meniscal tear, chondromalacia)
- Visualization: View retropatellar fat pad and posterior aspect of patellar tendon
- Debridement:
- Shaver used to resect retropatellar fat pad (visualize proximal tendon insertion)
- Identify "boggy" or degenerate area at inferior pole (proximal posterior tendon)
- Resect focal degenerative tissue
- Some surgeons perform inferior pole osteoplasty (resecting bony beak)
Advantages:
- Smaller incisions
- Faster rehabilitation
- Addresses intra-articular pathology
- Visualizes posterior tendon (site of pathology) without disrupting anterior fibers
Arthroscopy is increasingly preferred for its diagnostic utility and lower morbidity.
Complications
Complications Management
| Complication | Risk Factors | Management |
|---|---|---|
| Tendon Rupture | Steroid injections, aggressive early load | Surgical repair (quad/hamstring augmentation) |
| Persistent Pain | Inadequate resection, wrong diagnosis | Revision surgery vs salvage |
| Infrapatellar Numbness | Damage to infrapatellar branch of saphenous nerve | Observation (often permanent) |
| Infection | Open surgery | Antibiotics +/- debridement |
Tendon Rupture:
- The most devastating complication
- Rare in virgin cases, risk increases with multiple steroid injections
- Requires complex surgical reconstruction (often needs augmentation due to poor tissue quality)
Saphenous Nerve Injury:
- Infrapatellar branch runs transversely across proximal tibia/tendon
- Transverse incisions risk injury causing lateral numbness
- Longitudinal incisions safer
Postoperative Care and Rehabilitation
- Goal: Wound healing, pain control
- WBAT with crutches if needed
- ROM as tolerated
- Isometric quads
- Goal: Normal gait, full ROM
- Closed chain strengthening
- Cycling
- Proprioception
- Goal: Hypertrophy and strength
- Start eccentric loading program
- Increase resistance
- Single leg squats
- Goal: Return to sport
- Plyometrics initiation
- Sport-specific drills
- Return to play when strength over 90% contra-lateral side
Recovery is Slow
Patients must be counseled that surgery is NOT a quick fix. Biology of tendon healing combined with need for strength recovery means return to sport typically takes 4-6 months.
Outcomes and Prognosis
- Conservative: 60-80% success rate with proper eccentric program
- Surgical: 70-90% good/excellent results
- Return to Play:
- 50-60% return to previous level of sport
- Many return to sport but at a lower level or with residual symptoms
- Refractory cases: Consider other diagnoses (Hoffa's fat pad, plica) or look for biomechanical contributors (hip/ankle).
Evidence Base
- Systematic review showing no significant difference between eccentric and concentric exercise for pain/function.
- BUT eccentrics on a decline board showed superior results compared to flat ground.
- Randomized trial comparing corticosteroid vs eccentric rehab.
- Steroid group had good short term relief but significantly worse outcomes at 6 months and higher recurrence.
- MRI showed atrophy in steroid group.
- Systematic review of PRP for chronic tendinopathy.
- Found no significant benefit of PRP over control/eccentrics alone regarding pain or function.
- Comparison of surgical vs conservative treatment.
- No significant difference between surgery and eccentric strength training at 12 months.
- Surgery reserved for failed conservative care.
- Use of 25-degree decline board resulted in greater improvement in VISA-P scores compared to flat ground squats over 12 weeks.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Elite Basketball Player with Knee Pain
"A 24-year-old professional basketball player presents with 6 months of anterior knee pain. It warms up during play but hurts significantly afterwards. He is struggling to dunk. How do you assess him?"
Failed Conservative Management
"This patient has failed 6 months of supervised eccentric rehab and shockwave therapy. MRI shows focal mucoid degeneration at the proximal posterior tendon. Discuss surgical options."
Mechanism of Decline Squats
"Why do we prescribe decline board squats specifically? What is the biomechanical rationale?"
MCQ Practice Points
Pathology
Q: What is the primary histological finding in patellar tendinopathy? A: Angiofibroblastic hyperplasia and mucoid degeneration, with a distinct absence of inflammatory cells (tendinosis, not tendinitis).
Classic Sign
Q: What is Bassett's Sign and what does it indicate? A: Tenderness at the inferior pole of the patella in full extension that disappears in 90 degrees of flexion. It is pathognomonic for patellar tendinopathy.
Contraindication
Q: Why are corticosteroid injections contraindicated in the patellar tendon? A: They inhibit collagen synthesis and cause necrosis, leading to a significantly increased risk of acute tendon rupture.
Imaging Findings
Q: What are the characteristic ultrasound findings? A: Thickening of the tendon, hypoechoic areas (focal degeneration), and Doppler flow (neovascularization) which correlates with pain.
Rehabilitation
Q: What is the gold standard rehabilitation protocol? A: Eccentric strengthening, specifically using a 25-degree decline board to isolate the patellar tendon mechanism.
Classification
Q: What defines Stage 3 in the Blazina classification? A: Pain during and after activity that causes a decrease in sports performance. This is often the tipping point for considering surgery.
Australian Context
- Epidemiology: High prevalence in AFL (jumping/landing) and Netball.
- VISA-P: Developed in Victoria (Victorian Institute of Sport Assessment), is the global standard outcome measure.
- Research: Australia (Prof. Jill Cook, Purdam) is a world leader in tendinopathy research ("Donut" theory, continuum model).
- Injections: PRP is widely available but not Medicare rebated for this indication (out of pocket cost).
- Referral: Sports Physicians often manage conservative phase (PRP/shockwave) before surgical referral.
Patellar Tendinitis Essentials
High-Yield Exam Summary
Key Facts
- •Degenerative process (tendinosis), NOT inflammatory
- •Inferior pole of patella is classic site
- •Bassett's sign: Tender extension, non-tender flexion
- •Decline board eccentric squats = Gold Standard rehab
Must Know
- •NO STEROIDS (rupture risk)
- •VISA-P score is key monitoring tool
- •Surgery only after 6 months failed rehab
- •Return to sport takes 4-6 months post-op
Imaging
- •Ultrasound: Hypoechoic, thick, Doppler flow
- •MRI: T2 high signal posterior proximal tendon
- •X-ray: Usually normal (rule out other causes)
- •Doppler flow correlates with active pain
Surgical Options
- •Arthroscopic debridement (posterior tendon)
- •Open debridement
- •Tenotomy
- •Inferior pole osteoplasty (if impingement)