1
Background
Patellar tendinopathy (PT) is a common syndrome encountered in sports medicine. The symptoms are located in the distal extremity of the patella or in the proximal patellar tendon [ ] ( Fig. 2.1 ).
They can be intense and lead to stoppage of sports activity.
This condition is related to sports that involve frequent jumping such as volleyball and basketball, which explains why this condition is also called jumper’s knee [ ].
Repetitive jumping results in a considerable pressure on the knee extensor mechanism. The main pathophysiologic phenomenon in PT is tendinosis, which is a degenerative rather than an inflammatory disorder. Therefore, the use of the term tendinitis is not appropriate to describe this injury.
Prevalence of PT in professional volleyball players has been reported to be at 45% and 32% in professional basketball players [ ]. In other sports, such as soccer, in which jumping is not the main activity, PT has been reported in up to 2.4% of players [ ].
PT has been reported to have extrinsic and intrinsic risk factors. They include anthropometric factors, such as a high body mass index, a large abdominal circumference, limb-length difference, and flat foot [ ]. Biomechanical factors such as weak quadriceps muscles and inextensibility or tightness of the quadriceps and hamstring muscles are also associated with PT. Gender and some factors associated with the sport itself, including the training surface, were not found to be correlated with the development of PT [ ].
Patients typically present with an activity-related anterior knee pain that is precisely localized to the distal pole of the patella and the proximal end of the patellar tendon. The onset of the pain is usually insidious.
The diagnosis is mainly clinical, but imaging is needed when the symptoms are not typical.
The conservative management of PT is commonly sufficient to relieve symptoms. Surgical treatment is indicated for refractory cases.
2
Synonyms
Patellar tendinitis
Patellar tendinosis
Patellar chondropathy
Partial rupture of patellar ligament
3
Clinical Study
3.1
Symptoms
Patients with PT usually report a well-localized anterior knee pain that is related to the intensity of activity [ ].
Pain is usually insidious and aggravates gradually. It may be precipitated by an increase in the frequency or intensity of repetitive extension movements of the knee.
Initially, pain may present as a dull ache at the beginning of sports activities or after their accomplishment. This initial symptom may be ignored as it disappears during the activity [ ]. With continued use, however, pain can progress to be present during activity and interfere with performance significantly.
In some cases, there is a constant painful sensation at rest and at night that alters sleep [ ].
Other common complaints are pain with prolonged sitting and when using the stairs [ ].
3.2
Physical Examination
On clinical examination, the most frequent finding is patellar tendon tenderness [ ]. This tenderness is typically located at the inferior pole of the patella that is influenced by knee position [ ]. With the knee flexed to 90°, the tendon is placed under tension, and tenderness significantly decreases and may disappear altogether so the patellar tendon should be palpated in relaxed full-knee extension or with slight knee flexion ( Fig. 2.2 ).
Mild isolated pain should not be given much significance as it may be a normal finding in active athletes [ ].
Stretching and resisted contraction of the quadriceps may reproduce the patient’s usual pain ( Fig. 2.3 ).
Patients with chronic symptoms may exhibit weakness of the quadriceps, with the vastus medialis obliquus portion being the most commonly affected.
Functional strength testing of the quadriceps may be performed by asking the patient to perform one-legged step-downs [ ]. The strength of the calf can be assessed by performing single-legged heel raises. A jumping athlete should be able to perform a minimum of 40 raises [ ]. During both activities, the onset of fatigue and the quality of movement should be monitored and both activities should be performed bilaterally.
To reproduce PT symptoms, a useful functional test is the decline (30 degrees) squat test. This test places greater load on the patellar tendon than does a squat on level ground [ ]. The objective measurement during this test can be obtained by determining the number of decline squats before the onset of pain and asking the athlete to indicate the level of pain on a visual analog or verbal reporting scale. An alternative method of objectively assessing an athlete with PT is to use the Victorian Institute of Sport Assessment scale [ ]. This scale provides a numerical index of the severity of PT by assessing both pain and function. A maximum score of 100 indicates full, pain-free function (Annex 2).
4
Differential Diagnosis
4.1
Retinacular Pain
Patients with patellofemoral malalignment frequently complain of dull aching or pain in the anterior knee that is worsened by patellar retinaculum tensioning.
4.2
Fat Pad Lesion
The patient presents with pain on either side of the patellar tendon, where the fatty tissue sits. The pain may be worse with jumping, prolonged standing, or any other position with knee hyperextension. Besides, the area around the patellar tendon may be slightly swollen. Fat pad impingement is not associated with clicking, locking, or instability.
4.3
Lipoma Arborescens
This condition is characterized by an insidious onset of painless swelling of the affected joint, usually persisting for many years, followed by progressive pain accompanied by intermittent episodes of joint effusion.
4.4
Infrapatellar Bursitis
Symptoms of bursitis commonly include swelling and anterior knee pain that is worsened with flexion and usually occurring at night or after activity.
4.5
Partial Anterior Cruciate Ligament (ACL) Tear
A certain degree of laxity is found on ligamentous laxity tests of the knee.
4.6
Entrapment of the Saphenous Nerve
The patient usually complains of pain in the anteromedial aspect of the knee. The physical examination reveals a positive Tinel’s sign on the medial aspect of the knee and pressure over this area reproduces the patient’s pain.
5
Imaging
5.1
Standard X-rays
The use of radiographs during initial evaluation is limited since radiographic changes are rarely present during the first six months of PT evolution [ ].
When radiography is performed, the examination generally includes anteroposterior, lateral, and sunrise patellar views [ ].
Possible findings include radiolucency at the tip of the patella and an elongation of the involved pole. On occasions, calcification of the involved tendon and irregularity or avulsion of the patellar pole may be seen in the late stages [ ].
5.2
Ultrasound
Ultrasound (US) provides an available, quick, and inexpensive method of imaging for the patellar tendon.
In suspected PT cases, US can be used to confirm the existence and location of intratendinous lesions. These lesions are reflected by decreased echogenicity, typically in the deep posterior portion of the tendon adjacent to the lower pole of the patella [ ].
Other common findings on US include tendon thickening, irregularity of the tendinous envelope, intratendinous calcification, and erosion of the patellar tip [ ].
It has been shown that there is no correlation between the severity of tendinopathy symptoms on clinical grading systems and tendon appearance on US [ ].
5.3
Magnetic Resonance Imaging
On magnetic resonance imaging (MRI), PT is characterized by a focal increase in signal within the tendon as well as an alteration in its size [ ].
Increased thickening of the patellar tendon on MRI is present in all patients resistant to conservative therapy. An anteroposterior diameter of 7 mm has been suggested as a limit between symptomatic and asymptomatic tendons ( Fig. 2.4 ).
