1
Background
Biceps femoris (BF) muscle injuries are common sports injuries that can affect both recreational and elite athletes [ ].
These injuries have gained considerable attention because of the time lost from sports and the burden on both athletes and their teams. Although fairly common, these types of injuries are considered a difficult entity to treat. The first step in treating these injuries is an accurate and rapid diagnosis.
The majority of these injuries are limited to tendon strains, but if diagnosis is not made early, the treatment results and the outcome will be badly affected [ ]. These injuries have a tendency to recur, especially in elite athletes, and some patients may develop chronic symptoms.
The exact rate of BF injuries varies as a result of different definitions of what qualifies as an injury and the diversity of populations studied [ ]. In general, the prevalence of all hamstring injuries ranges from 8% to 25% of all athletes’ injuries [ , ]. Epidemiological data regarding BF injuries are currently lacking.
The prevalence of BF tendinopathy is higher in sports associated with running and fast acceleration which result in increased stress on the BF muscle-tendon junction unit. These injuries are frequently seen in sports such as soccer, American football, gymnastics, and water skiing [ ]. Tendon strains are considered the most common form of injury, while complete ruptures occur less frequently [ ].
Multiple risk factors have been described [ ]. Modifiable factors include muscular fatigue, low muscular strength, lack of warm-up, higher level of competition, and low hamstring to quadriceps strength ratio. Nonmodifiable factors include age, previous injury, and black race [ ]. A previous hamstring injury is considered the greatest risk factor and is associated with an increase in the rate of reinjury [ ]. Age was reported to be an important independent predictor of hamstring injury [ ]. In elite athletes, speed and kicking positions have been found to increase the risk of injury [ ].
Distal BF tendon injuries are less frequent than proximal ones, even though they share the same mechanism, which includes both eccentric muscular contraction during the stance phase of running and overstretching the leg [ ].
2
Synonyms
BF Strain.
BF partial rupture.
BF tendinosis
3
Clinical Study
3.1
Symptoms
History is characterized by the absence of acute trauma. Usually there is an insidious onset of posterior knee pain, and a difficulty in weight-bearing activities. Patients may rarely have difficulty sitting as a result of pain. In the early phase of the injury, walking can be hard and running is often impossible [ ]. Some patients can also present with neuropathic pain in the posterior thigh. This clinical presentation called gluteal sciatica is related to compression of the sciatic nerve resulting from scarring and typically involves mainly the posterior cutaneous branch of the sciatic nerve ( Fig. 6.1 ).
Patients often report weakness in knee flexion associated with pain and stiffness. Depending on the severity of the condition, patients may have a loss of active flexion and in some cases may have difficulty with active extension. In addition, cramps and spasms in the posterior aspect of the thigh are possible.
Patients with chronic injuries usually present with profound weakness rather than pain. In addition, gluteal sciatica symptoms are more frequent in the chronic phase due to excessive scarring in the area of injury and subsequent nerve irritation [ ].
3.2
Physical Examination
Identifying a BF injury during physical examination can be difficult because of the deep location of the muscle within the thigh. However, there are some signs that may guide the examiner toward the diagnosis. In case of a rupture, a palpable defect can be occasionally felt along the course of the tendon.
An important part of the physical examination is testing knee range of motion (ROM) and the strength of the affected muscle and comparing these findings with those on the contralateral side.
Ideally, the patient should be lying prone with the hip positioned in 0 degree of extension. Knee flexion is then examined with resistance applied at the heel with the knee in 15 degrees and 90 degrees of flexion ( Fig. 6.2 ).
Pain provoked by the examination or weakness is considered a positive finding [ ].
Hip flexion and knee extension should be examined to test BF flexibility which can be limited by pain [ ] ( Fig. 6.3 ).
4
Differential Diagnosis
4.1
Lateral Osteoarthritis of the Knee or Osteochondral Defects
Pain is rather felt as intraarticular and patients present with a swelling of variable amounts.
4.2
Injury to the Lateral Collateral Ligament or Posterolateral Corner of the Knee
A history of acute trauma is usually found and signs of instability may be present.
4.3
Lateral Meniscal Tears
Locking sensations are frequently present and meniscal tests are positive.
4.4
Iliotibial Band Syndrome
Lateral knee pain and a snapping sensation of the knee in runners and cyclists is suggestive of this syndrome. Specific clinical tests allow to confirm the diagnosis.
5
Imaging
5.1
Standard X-rays
All young athletes complaining from an acute onset of pain should be evaluated with radiographs to identify avulsion fractures [ ].
Other findings include soft tissue swelling, but it is usually difficult to appreciate radiographically. At the chronic stage, calcifications may appear in the tendon area, but they are quite uncommon.
5.2
Ultrasound
Ultrasound (US) has been reported to be an excellent tool for diagnosing BF tendinopathy.
It is easily accessible and is less expensive than magnetic resonance imaging (MRI). However, it is highly operator-dependent, and diagnosing small injuries is sometimes challenging.
Furthermore, in some cases, it can be difficult to differentiate scar tissue of an old injury from an acute injury [ ].
5.3
CT Scan
Computed tomography (CT) scan has been used by some authors to evaluate BF tendinopathies in their acute stages. In fact, it allowed to accurately localize and determine the extent of the lesions. The affected area appeared as a zone of low density suggesting the presence of edema [ ].
5.4
Magnetic Resonance Imaging
MRI is considered as the standard modality for the diagnosis of distal BF injuries [ ]. This is particularly true in cases of recurrent injuries [ ].
It is also crucial for determining the extent of the injury and differentiating between partial and complete tears and the amount of retraction in case of tendon rupture [ , ].
Findings include high signal intensity areas in acute injuries on T2-weighted sequences as a result of surrounding edema.
The same areas appear as intermediate signal zones on T1-weighted sequences [ ]. MRI aspects of chronic lesions are very diverse, but it is important to mention that axial sequences are the most helpful in their diagnosis.
MRI findings have also been shown to be helpful in predicting the duration of the postinjury rehabilitation period by correlation to the length and cross-sectional area of the injury [ ]. Cohen et al. found that MRI predictors for increased time away from sports included muscle retraction, and a long high signal on sagittal plane on T2-weighted sequences [ ].
6
Treatment
6.1
Conservative Treatment
RICE protocol should be followed in the initial management of this tendinopathy.
6.1.1
Activity modification
The use of compressive clothing, incorporation of warm-up and cool-down exercises before and after sports activities, and joint proprioception training have been reported as factors that can decrease the risk of BF tendinopathy and their recurrence [ ].
6.1.2
Medical treatment
Nonsteroidal antiinflammatory drugs (NSAIDs) have been suggested as an option for reducing the inflammation and pain perception, but the effect of such drugs on reducing the intensity of symptomatic aspects of BF muscle injuries has not been studied [ ].
6.1.3
Rehabilitation
The main purpose of any rehabilitation program included in the operative or nonoperative treatment of BF injury is to restore the patient’s functional capacities.
Multiple studies have shown the effectiveness of eccentric strengthening in reducing the risk of sustaining this type of injury, both as a preventive measure and in patients with established strains, especially when preceded by an adequate duration of warm-up stretching [ ].
Exercises directed at trunk stabilization and core strengthening have also been shown to reduce the risk of injuries in this muscle (134). Neuromuscular control and eccentric strengthening exercises, such as Nordic hamstring exercises are recommended in rehabilitation programs for patients with acute injuries [ ] ( Fig. 6.4 ).
