What is jumper's knee (patellar tendinopathy)?

Jumper's Knee (Patellar Tendinopathy)

Jumper's knee is a common overuse injury characterized by activity-related anterior knee pain due to degeneration of the patellar tendon, most frequently occurring in athletes who participate in jumping sports. 1

Definition and Pathophysiology

• Patellar tendinopathy (jumper's knee) is a degenerative condition of the patellar tendon rather than an inflammatory disorder, making the term "tendinitis" inappropriate 2
• The condition involves degeneration of the normally highly arranged collagen fiber structure in the tendon, resulting in collagen disorientation and fiber separation 3
• Most cases represent chronic tendinosis rather than acute inflammation, as patients typically present after prolonged symptoms when acute inflammation has subsided 3

Epidemiology and Risk Factors

• Affects both athletes and non-athletes, with highest prevalence in jumping sports like volleyball and basketball 1
• Repetitive loading of the patellar tendon places jumping athletes at greatest risk 3
• Risk factors vary based on sex, playing conditions, type of sport, playing level, and personal characteristics 1
• Landing biomechanics play a significant role, with stiff landing patterns and short landing times associated with increased risk 4

Clinical Presentation

• Insidious onset of load-related localized pain on the anterior aspect of the knee, coinciding with increased activity 3
• Pain is typically described as "sharp" or "stabbing" and is exacerbated by navigating stairs and prolonged sitting 3
• In early stages, pain is present during activity but may subside after a warm-up period 3
• Pain gradually increases in intensity and duration, potentially becoming present at rest in later stages 3
• Most patients report engaging in a new activity or increasing intensity of current activity before symptom onset 3

Physical Examination

• Examination reveals well-localized tenderness at the inferior pole of the patella 3
• Pain can be elicited at the inferior pole of the patella with the leg fully extended using resisted leg extension 3
• A decline squat test places increased load on the patellar tendon and often reproduces the patient's pain 3
• Inspection may show muscle atrophy (in chronic cases), asymmetry, swelling, or erythema 3
• Joint effusions are uncommon and suggest possible intra-articular pathology 3

Diagnostic Imaging

• Diagnosis is primarily clinical, but imaging can be useful for confirmation 1
• Ultrasonography shows tendon thickening, decreased echogenicity, and calcification; more specific (94%) than sensitive (58%) 3
• MRI shows changes consistent with chronic degenerative tendon changes with moderate sensitivity (78%) and specificity (86%) 3
• Plain radiography is typically unable to demonstrate soft-tissue changes but may reveal bony abnormalities 3

Treatment Approach

Conservative Management (First-Line)

• Eccentric strengthening exercises should be the primary treatment approach as they reduce symptoms, increase strength, and promote tendon healing 3, 5
• Relative rest to decrease repetitive loading of the damaged tendon is essential, but complete immobilization should be avoided 3, 5
• Deep transverse friction massage is recommended to reduce pain 3, 5
• Ice application through a wet towel for 10-minute periods provides short-term pain relief 5
• Stretching exercises for involved muscles improve flexibility and reduce tension on the tendon insertion 5
• Correction of biomechanical issues with appropriate orthotics may be beneficial, particularly if excessive foot pronation or pes planus is contributing 5

Advanced Interventions

• Corticosteroid iontophoresis can be effective for treatment of patellar tendinosis pain and function 3
• Various injection therapies (platelet-rich plasma, corticosteroids, autologous blood) show promising results but have variable evidence 6
• Corticosteroid injections may provide faster short-term relief but don't improve long-term outcomes and could potentially weaken tendon structure 5
• Extracorporeal shock wave therapy is a safe, noninvasive option for pain relief in chronic cases 3

Surgical Management

• Surgery is indicated for cases refractory to 3-6 months of conservative treatment 3
• Both open and arthroscopic approaches are effective, though arthroscopic surgery results in faster recovery 2
• Most patients can return to previous level of sports 8-12 weeks after surgery 7

Treatment Algorithm

1. Initial phase (1-2 weeks): Relative rest from aggravating activities, ice application, gentle stretching 5
2. Intermediate phase (2-6 weeks): Progressive eccentric strengthening exercises, continued stretching program, deep transverse friction massage, address biomechanical issues 5
3. Advanced phase (6+ weeks): Sport-specific exercises, gradual return to normal activities, maintenance program to prevent recurrence 5
4. Refractory cases: Consider advanced interventions (injections, shock wave therapy) or surgical consultation after 3-6 months of failed conservative treatment 3, 6

Prevention Strategies

• Employ a flexible landing pattern with adequate post-touchdown range of motion during jumping activities 4
• Improve kinetic chain functioning through appropriate strength and flexibility training 4
• Implement eccentric exercise programs as preventative measures for high-risk athletes 4
• Regular screening is essential, especially for elite athletes 1