Dr. Dressendorfer is a physical therapist, adjunct professor of exercise physiology at University of Alberta, Edmonton, and an editor for DynaMed. Dr. Alper is medical director of clinical reference products for EBSCO Publishing, in Ipswich, Mass., and editor-in-chief of DynaMed (www.dynamicmedical.com), a database of comprehensive updated summaries covering nearly 2,000 clinical topics.

• Patellar-tendon microlesions, increased fibrosis, and loss of tensile strength; characterized by pain and stiffness
• Common reason for interrupted training and competition in elite athletes

ICD-9 code
• 726.64 Patellar tendinitis

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Who is most affected
• Physically active older teenagers and young adults
• Athletes who jump, e.g., volleyball, or kick, e.g., soccer

• Commonly seen in athletes, especially those who jump
• Developed in 14% of physical-education students followed over two years
• Second-most common injury in female basketball players and military recruits during basic training

• Repetitive or sudden overload that exceeds reparative capacity of tendon
• Jumping and landing from jumps

Likely risk factors
• Inflexibility of the quadriceps and hamstring muscles
• Inappropriate amount and intensity of training
• Hardness of playing surface
• Limited evidence of intrinsic biomechanical risk factors

• Degenerative tendinosis, not an inflammatory tendinitis
• Failed healing response indicated by collagen disorganization, fibrosis, fibroblastic cells, and neovascularization

• Sudden rupture if severe or prolonged, especially with continued activity
• Chronic irreversible scarring

Associated conditions
• Patellofemoral pain resulting from chondromalacia or subluxing patella
• Rheumatoid arthritis
• Systemic lupus erythematosus
• Anabolic steroid use

Clinical evaluation
• Ask about previous knee problems or trauma (diagnosis, x-rays, therapy).
• Localized anterior knee pain, frequently at proximal insertion to base of patella, precipitated by activity or prolonged knee flexion
• While elevating patella, palpate deep fibers at inferior pole for point tenderness.
• Provocation of symptoms on resisted knee extension, or with passive knee flexion and hip extension
• Minimal or no effusion, redness, or warmth
• Evaluate patellar mobility and tracking.
• Assess strength of quadriceps.
• Knee range of motion may be normal.
• Assess flexibility of quadriceps to pain onset.
• Assess flexibility of hamstring (straight-leg raise >70°, 90° for athletes).
• Consider assessment of knee function with Victorian Institute of Sport Assessment (VISA) score.

Rule out
• Referred pain from hip or back
• Patellofemoral pain
• Patellar tendon impingement
• Chondromalacia patella
• Osgood-Schlatter disease, if teenager and painful enlargement at tibial tuberosity
• Degenerative joint disease of the knee
• Meniscus tear
• Osteochondritis dissecans
• Iliotibial-band friction syndrome

Imaging studies
• Not needed except to rule out other potential causes
• Bone scan: increased density in patellar tendon
• Ultrasound: hypoechoic region at base of patella

Treatment overview
• Discontinue aggravating activities/factors.
— In athletes, relative rest with partial reduction in training intensity and volume
• Conservative therapy should be shifted away from anti-inflammatory strategies toward functional rehabilitation with eccentric tendon strengthening as a key element.
— Eccentric quadriceps strengthening (squat exercise) on decline appears more effective than therapeutic ultrasound or transverse friction.
— Eccentric quadriceps strengthening, but not concentric training, appears to reduce pain.
• Stretching normalizes quadriceps and hamstring flexibility.
• Analgesic measures—ice pack, oral or topical nonsteroidal anti-inflammatory drugs (NSAIDs), patellar tendon counterforce strap


• Anti-inflammatories do not provide long-term benefit; inflammation is not a major part of the pathology.
• Topical NSAIDs may be effective for associated musculoskeletal pain.
• Injections
— No strong evidence for benefit or harm
— Should be peritendinous if tried

Additional therapies to consider
• Ultrasound-guided sclerosis of neovessels
• Ultrasound-guided peritendinous steroid injection
• Hyperthermia at 434 MHz may reduce pain more than conventional ultrasound.
• Extracorporeal shock wave therapy might be effective for improving functional outcome.
• Evidence on surgical treatment inconclusive

• Generally good outcome with activity modification, physical therapy, and strengthening


• Adequate warmup prior to running or jumping
• Stretching program to maintain quadriceps and hamstring flexibility
• Correct biomechanical errors in jumping technique.
• Limited evidence regarding interventions for preventing lower-limb soft-tissue injuries in runners

See www.dynamicmedical.com for references.