Patellar tendinitis is a syndrome of overuse characterized by anterior knee pain brought on by running, jumping, and kicking activities. Blazina's original paper in 1973 coined the term, "jumper's knee," which is generally felt to be synonymous with patellar tendinitis. Blazina1 believed that there were four progressive stages of patellar tendinitis (Table 1). With each advancing stage, athletic performance was adversely affected and tendon damage became more severe. Discomfort is usually reported at the start (generally getting better after a warm-up period) and finish of an athletic competition.
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Table 1. Classification of Jumper's Knee.
|Stage 1||Pain after sport. |
|Stage 2||Pain at beginning, disappears with warm-up, reappears with fatigue.|
|Stage 3||Pain at rest, worsens with activity, unable to participate.|
|Stage 4||Patellar tendon rupture.|
In 1984, Stanish2 published a classification of patellar tendinitis based on athletic performance limitations (Table 2). As with Blazina's staging, each level more adversely affects the athlete's ability to participate. Stanish outlined an aggressive rehabilitation program to help strengthen the patellar ligament through a combination of stretching and eccentric strengthening exercises.
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Table 2. Stanish's Classification of Jumper's Knee.
| Level 1 ||No pain.|
| Level 2 ||Pain with extreme exertion only.|
| Level 3 ||Pain during and 1-2 hours after exertion.|
| Level 4 ||Pain during any athletic activity and 4 to 6 hours after; performance diminished.|
| Level 5 ||Pain immediately after the beginning of sports activity; withdrawal from activity.|
| Level 6 ||Pain during daily activities; inability to participate in any sports.|
The repetitive microtraumatic loads during sporting activities frequently exceed the tensile strength of the patellar tendon. These forces have been reported to be as high as 8,000 N to 9,000 N during running and landing from jumps. These microtears usually are located within the deep fibers near the inferior pole of the patella where the fibers are less elastic and more subject to elongation stresses.
There is a high frequency of patellar tendinitis reported in soccer, volleyball, basketball, and track. These sports require repeated impacts of the limb to the ground with the knee partially flexed. The excessive forces created as the foot leaves the ground during running (accelerations) or when the quadriceps contract during change of direction and while landing from jumps (deceleration) cause microtears of the tendon that lead to focal degeneration and chronic inflammation.
Pain is usually reported with bent knee activities, is localized to the patellar tendon, and increases with squatting and resisted knee extension, and with frequent activity on hard surfaces. Tenderness is better localized with the knee in extension (Puddu's sign) by pushing the patella distally and palpating the lower pole of the patella. Thickening and swelling of the inferior pole of the patella may be present. Quadriceps and hamstring tightness is usually observed. Most athletes may notice some mild crepitation or popping. There does not seem to be any correlation to malalignment, age, sex, degree of training, or years involved in the sport.
Jumper's knee can occur at both insertions of the patella. The most frequent location (80%) is at the patella tendon origin along the inferior pole. The majority of patients with this condition are less than 40 years old. Quadriceps tendinitis generally is seen after age 40 and occurs at the proximal pole of the patella. In adolescents, the weak link in the extensor chain is the lower pole of the patella (Sinding-Larsen-Johansson disease) or the tibial tubercle attachment (Osgood-Schlatter disease). These conditions are regarded as self-limiting but should be treated with relative rest.
The results of standard radiographs are usually normal. There will be an occasional elongated inferior tip or a fragmented inferior patellar pole (usually adolescent Sinding-Larsen-Johansson disease). Much less frequently, bone or calcific deposits may be seen. In the adolescent, a fragmented tibial tubercle confirms Osgood-Schlatter disease.
Magnetic resonance imaging is not routinely indicated in evaluating patellar tendinitis. Ultrasound is extremely sensitive, showing edema in combination with angiofibroblastic hyperplasia and fibrinoid necrosis. Intratendinous calcifications can be visualized. As in other areas, the ultrasound examination is extremely operator sensitive.
Many other conditions that cause anterior knee pain should be considered and evaluated during the examination. Several common disease processes include, but are not limited to, the following:
- Patellofemoral disorders
- Medial parapatellar plica inflammation
- Meniscal tears
- Fat pad inflammation (Hoffa's disease)
- Infrapatellar bursitis
Conservative treatment: Nonsurgical
Nonsurgical treatment is always recommended as the first choice of management in all stages and levels of patellar tendinitis except with complete rupture of the tendon. Stretching of the quadriceps and hamstrings is recommended to resolve tightness in the muscle tendon unit. A warm-up should include eccentric exercises (for example, mini-squats or lateral step-ups). Plyometrics can be incorporated into the warm-up routine to help increase tendon loads and ultimately increase the tensile strength of the tendon. Eccentric activity helps increase the elasticity and tensile strength of the muscle tendon unit. As discomfort disappears, the speed of the exercise should increase.
Cross-fiber friction and ice massages are beneficial. Ice should be used after any activity. Nonsteroidal anti-inflammatory medication can be used for several weeks during an acute exacerbation. Therapeutic modalities, such as ultrasound, electrical stimulation, and iontophoresis, also seem to help control pain and allow the progression of rehabilitation.
Various braces, straps, and taping techniques have been used to assist the athlete during athletic participation. These supports tend to stabilize the patella and apply compression to the tendon. The compression increases as the knee flexes, therefore decreasing the tensile forces on the tendon. The decrease in tendon forces results in less pain during and after the activity.
Intratendinous anti-inflammatory steroid injections should be avoided. There is a concern that further damage may occur due to collagen necrosis seen after injection. This may lead to an increased incidence of patellar tendon rupture.
The athlete should take an extended period of relative rest. He or she should avoid any extra high impact loads, such as bounding or springing activities. Improvement usually will be satisfactory (more than 90%) if the provocative stimulus can be avoided.
Surgical intervention only should be considered if conservative treatment has been attempted for a minimum of 6 months. If the athlete can no longer maintain appropriate participation in practice and game situations, surgical exploration and debridement of the tendon can be performed. Generally, prior to surgery, an MRI is used to rule out intra-articular pathology as a source of a patient's symptoms. The patellar tendon is explored and opened longitudinally to expose the degenerated tendon. All discolored, gelatinous material is removed and the inferior pole of the patellar can be excised (similar to anterior cruciate ligament graft harvest) and/or drilled to help stimulate a healing response in the scarified tendon. An aggressive rehabilitation program similar to that described above should be started within 3 to 4 weeks after surgery. High impact activity may require 4 to 6 months of intense postopertive rehabilitation.
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- Stanish WD, Curwin KS. Tendinitis: Its Etiology and Treatment. Toronto: Collanone Press; 1984.
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