1
Background
Microtraumatic quadriceps tendon injuries usually include conditions ranging from tendinosis to partial thickness tears to complete tendon rupture and less commonly recalcitrant tendinitis.
These lesions are relatively uncommon in painful knee conditions [ ]. In fact, in sports medicine practice, quadriceps tendinopathy is less common than the patellar one [ ]. Quadriceps tendinopathy and especially rupture should be kept in mind when investigating acute symptoms associated with the extensor mechanism of the knee [ ].
The quadriceps is a strong part of the extensor system of the knee, but it can be affected by degenerative changes, under the influence of local and systemic factors leading to tendinopathy and in some cases to spontaneous, partial, or complete rupture. For this reason, prevention and treatment of predisposing factors and early recognition can be helpful in identifying patients susceptible to rupture [ ].
Practicing regular sport activity in advanced ages and weight lifting sports are considered risk factors for quadriceps tendinopathy. Quadriceps tendon is biomechanically exposed to heavy loads stress and microtrauma resulting from deep squat exercises and sudden acceleration forces [ ].
Patients usually report an insidious onset of knee pain especially located at the superior pole of the patella. On examination of the knee, tenderness in the tendon insertion, painful resisted contraction and stretching allow to establish the diagnosis of tendinopathy.
All grades of quadriceps tendinopathy are usually treated conservatively. Conservative treatments include extracorporeal shock waves as well as autologous growth factors injection which are particularly effective [ ].
2
Synonym
Quadriceps tendinosis.
3
Clinical Study
3.1
Symptoms
Quadriceps tendinopathy may interfere with daily activities. Pain is usually felt when climbing the stairs, kneeling, and rising from a chair. Athletes may be unable to participate in running and jumping activities [ ].
Patients usually report an insidious onset of knee pain and may notice painful clicking. A burning sensation at the bone-tendon junction may be experienced [ ].
The pain is aggravated by activities resulting in load stress of the extensor mechanism, including bending, stair climbing, running, and jumping.
Reports of severe weakness are alarm features suggesting the possibility of a quadriceps tendon partial or complete rupture.
The quadriceps tendon rupture is more common in older subjects (>50 years) with associated systemic factors, such as obesity, gout, and local degenerative changes such as knee osteoarthritis [ ]. Patients with tendon ruptures are unable to walk without assistance and usually hold their leg as straight as possible.
The investigator should look for a history of renal insufficiency, primary or secondary hyperparathyroidism, diabetes, rheumatoid arthritis, gout, use of quinolones, corticosteroid injections, and anabolic steroids and obesity which impair and weaken the osteotendinous junction [ ]. Furthermore, a genetical predisposition is incriminated in case of bilateral rupture of the quadriceps tendon [ ].
3.2
Physical Examination
On examination of the knee, tenderness is localized along the superior pole of the patella and the quadriceps tendon.
Pain in the quadriceps tendon area may be reproduced by extreme knee flexion and by resisted knee extension ( Fig. 3.1 ).
The clinician should also look for a palpable defect, suggesting partial or complete rupture of the quadriceps tendon.
Neurologic examination findings are usually normal. Painful weakness is related to complete or partial tendon rupture. Stability of the knee is typically not affected.
Usually, a localized tenderness and thickening along the course of the tendon are clinically present.
Jolles et al. proposed a minimally invasive test that can clinically determine the integrity of the quadriceps tendon in its five distal centimeters, which was inspired by the O’Brien test for complete rupture of the Achilles tendon [ ]. With the patient lying in the supine position, in aseptic condition, a 25-gauge needle is inserted in a right angle through the skin of the thigh, at a midline point, 5 cm proximal to the superior pole of the patella. The needle is inserted gently through the skin until greater resistance is felt, so that the needle’s tip is just within the substance of the quadriceps tendon but without transfixing it.
A passive knee flexion and extension movement is then performed, and the movement of the needle is observed. Two distinct types of response may occur. If the needle pivots about its penetration point in the skin, the tendon is intact throughout its distal 5 cm. If the needle does not pivot (positive test), this indicates loss of continuity of the quadriceps tendon between its insertion and the position of the needle [ ].
Despite these clinical signs, misdiagnosis is frequent, ranging from 39% to 67% [ ].
4
Differential Diagnosis
4.1
Patellar Tendinopathy
Pain and tenderness are located next to the distal pole of the patella.
4.2
Patellar Fracture
A history of a direct trauma on the kneecap is usually found. Radiographic findings confirm the diagnosis.
4.3
Patellofemoral Syndrome and Chondromalacia Patellae
Pain is felt as retropatellar or peripatellar. It typically occurs with activity and often worsens when descending the stairs or hills or by prolonged sitting. Dull, aching pain, and/or a feeling of grinding when the knee is flexed are typically present in case of chondromalacia patellae.
4.4
Prepatellar Bursitis
Swelling in the peripatellar region alongside with pain in the anterior aspect of the knee are suggestive of prepatellar bursitis.
5
Imaging
5.1
Standard X-rays
Standard radiographs may have some diagnostic value for quadriceps tendinopathy and tendon tears. In the chronic stage of tendinopathy, they may show calcifications suggesting a recalcitrant tendinopathy. The abolition of the quadriceps shadow, the presence of a mass in the suprapatellar soft tissues secondary to tendon retraction, and the avulsion of a bony segment from the proximal pole of the patella are all typical radiographic features of tendon rupture. The low-riding patella or patella baja is another feature suggestive of quadriceps tendon rupture.
5.2
Ultrasound
The ultrasound (US) examination is a more effective method for diagnosing tendinopathy and rupture of the quadriceps tendon compared to traditional radiography [ ].
Thickening of the different layers and loosening of the fibrillar structure are pathognomonic signs of degenerative tendon disease [ ].
The US images of quadriceps tendinopathy can be extremely heterogeneous, from some degenerative alterations limited to a single layer of the tendon, to larger ones involving the whole tendon. In the first case, tendinopathy can be recognized as a hypoechogenic oval image while in the second one, a wider hypoechogenicity of the different collagen layers will be described.
Calcifications may be present in some cases and a pathologic hypervascularization phenomenon is seen in the acute stage.
The previous US findings are sometimes present in asymptomatic individuals and are considered as risk factor for the occurrence of painful symptoms in the future [ ].
5.3
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is an important instrumental method for quadriceps tendon evaluation. It is recommended before any surgical treatment [ ].
In case of partial rupture, at least one of the layers is still intact. The superficial layer is the most common site of injury, followed by the intermediate one [ ] ( Fig. 3.2 ).
When a total rupture occurs, there is an interruption of all the tendon layers, with a possible hematoma in the area of the lesion. In this case, MRI demonstrates a retracted proximal stump and a wavy look of the patellar tendon [ ].
In dynamic MRI, by the traction of the patella, it is possible to observe an increase in the interval between the two tendon stumps.
6
Treatment
6.1
Conservative Treatment
The RICE protocol should be followed for the initial management of this tendinopathy especially in the acute phase.
6.1.1
Activity modification
A conservative management of this condition should include relative rest with modification of pain-provoking activities and a reduction in total training hours to limit progression of the pathology. Complete stoppage of sports activity should be avoided given its negative effects.
Lower limb biomechanical correction can reduce quadriceps tendon loading by improving its energy-absorbing capacity.
6.1.2
Medical treatment
Analgesics such as paracetamol may be useful to reduce painful symptoms especially in the acute stage. Antiinflammatory medications are among the most common pharmacological treatments used in quadriceps tendinopathy, especially oral nonsteroidal antiinflammatory drugs (NSAIDs) and corticosteroids. The use of both has been debated considering that tendinopathy has a noninflammatory mechanism.
6.1.3
Rehabilitation
Quadriceps tendinopathy is responsive to the same physiotherapy treatments of patellar tendinopathy (PT) [ ].
Deep friction massage, US, and extracorporeal shock wave therapy (especially in case of calcifications) represent valid physical modalities for treating quadriceps tendinopathy [ ].
Eccentric exercises play a key role in the conservative treatment of this tendinopathy. Dimitrios et al. [ ] demonstrated that the combination of eccentric training and quadriceps stretching exercises would be superior to eccentric training alone, in order to reduce pain and improve function ( Fig. 3.2 ).
