An 22 yo athlete changes their training regiment from cardio intensive to strength intensive training. They are lifting heavy weights before and after training. On the 10th day of weight intensive training, they feel a pull in their left anterior thigh. There is no pain with walking.
On exam, there is no obvious deformity. Point tenderness at the left distal myotendinous junction. Pain with passive stretching. Some fluid around the injury.
Figure 1: A sagittal T2-weighted MRI of the left leg. Note the diffuse intramuscular fluid at the myotendinous junction of the rectus femoris (arrows).
Figure 2: Two axial T2-weighted MRI of the left leg. Bull’s eye sign: note the intramuscular edema of the inner bipennate muscles surrounding the central tendon of the rectus femoris (arrows).
Diagnosis: Grade 2 myotendinous junction (central tendon) strain of the left rectus femoris.
The quadriceps muscle group is comprised of four muscles: the rectus femoris, the vastus medialis, vastus intermedius and the vastus lateralis. Distally, the tendons of these muscles merge to form the quadriceps tendon.
Of these muscles, the rectus femoris is the most commonly strained and has the most complex anatomy. It acts to extend the lower leg at the knee and flex the thigh at the hip. The rectus femurs has two tendinous origins: the direct head, which arises from the anterior inferior iliac spine (AIIS), and the indirect head, which arises from the superior acetabular ridge and the posterolateral aspect of the hip joint capsule. The direct head extends along the proximal 1/3 of the muscle and gives rise to unipennate muscle and blends with the anterior fascia. The indirect head courses through the proximal 2/3 and contributes to the deep, central intramuscular tendon and gives rise to a bipinnate muscle which is surrounded by unipennate muscle (see figures 3 and 4).
The rectus femoris is prone to injury because it crosses two joint, has a high proportion of type 2, fast twitch muscle fibres and because in sports like soccer, football and martial arts it undergoes powerful eccentric contraction (during kicking motion) while being passively stretched during the onset of forward swing phase.
Acute rectus femoris injuries present as the feeling of tearing which stops the athlete from activity. Examination reveals that stretching, palpation at the site of injury, and resisted knee extension are painful. Burning or stinging sensations may be felt on the anterior thigh in the case of femoral nerve tension.
The most common site of rectus femoris injury is the myotendinous junction near the knee joint. Other locations of injury are centred around the indirect and direct heads at the myotendinous junctions, or, less commonly, the myofascial junction at the periphery of the muscle. Proximal tendon injuries can be associated from avulsion fractures of the AIIS. Other injuries to the quadriceps mechanism include muscle contusion, vastus muscle strain, and quadriceps tendon tear.
To diagnose and monitor the resolution of rectus femoris injuries, ultrasonography and MRI can be used. Myotendinous strains can be graded by MRI. Grade 1 tears show an intact myotendinous junction and is defined by the presence of focal or diffuse high-intensity signal at the myotendinous junction. Grade 2 tears show partial disruption of the myotendinous junction with interstitial high-intensity signal. Chronic injuries may present with low signal representing either fibrosis or haemosiderin. Grade 3 tears show complete myotendinous disruption with or without retraction.
In a case series of rectus femoris central tendon injuries published in 2009 by Balius et al. (4) – a difference was noted between proximal injuries and distal injuries in time absent from sporting participation. Proximal injuries of 4.0 cm length resulted in an absence time of 45.1 days compared to 32.9 days in distal injuries measuring 3.9 cm. Return to unrestricted activity prognosis for this cases would be 4-6 weeks. Initial treatment includes rest, ice, compression and elevation for the first 24-48hrs. Crutches in cases of severe strains that are unable to weight bear. Pain and inflammation can be controlled with NSAIDS. Progressive rehabilitation exercises, including ROM, gentle stretching and isometric muscle contraction are recommended.
Figure 3: A cross-sectional illustration of the rectus femurs tendinous anatomy.
Figure 4: Illustration in the transverse plane of the concept of inner bipennate and outer unipennate muscles originating from the indirect and direct heads, respectively.
Lucas Nguyen (Dec 16, 2018 PR ND)
1) Mendiguchia J, Alentorn-Geli E, Idoate F, et al. Rectus femoris muscle injuries in football: a clinically relevant review of mechanisms of injury, risk factors and preventive strategies. Br J Sports Med 2013;47:359-366.
2) Von Fange TJ. (Last updated: 2017, Dec. 6th). Quadriceps muscle and tendon injuries. Retrieved from https://www-uptodate-com.
3) Kerr RM. (Last updated: 2014, May). MRI of Rectus Femoris / Quadriceps Injury. Retrieved from http://radsource.us.
4) Balius R1, Maestro A, Pedret C, Estruch A, Mota J, Rodríguez L, García P, Mauri E. Central aponeurosis tears of the rectus femoris: practical sonographic prognosis. Br J Sports Med. 2009 Oct;43(11):818-24. doi: 10.1136/bjsm.2008.052332. Epub 2009 Jan 27.