The rectus femoris muscle is one of the four quadriceps muscles located within the knee joint, acting to flex (bend) the hip while simultaneously extending (straightening) it.
It arises from the anterior inferior iliac spine and ilium above the acetabulum and attaches via quadriceps tendon to the patella. The rectus femoris is divided into direct head and indirect head sections; mild lesions on axial T1-weighted images typically display as bands of edema at their interface.
Direct Head
The rectus femoris is one of the quadriceps muscle group that extends the knee joint. Originating at the anterior inferior iliac spine and ilium of the pelvis, this muscle attaches onto the patella via its quadriceps femoris tendon which in turn connects with patella ligament. Innervated by posterior femoral nerve and supplied with water by branch from lateral circumflex femoral artery; innervated by posterior femoral nerve.
Since it consists of multiple muscles within itself, quadriceps muscle injuries are numerous and varied. One such type is known as “degloving,” in which muscular bellies dissociate from one direct head (Fig 2). Although rare but recurrent injuries occur from time to time, degloving tears are associated with functional limitations to quadriceps flexed hip position, as well as loss of function on one extending knee joint (Fig 3).
Anterior inferior iliac spine (AIIS) avulsion fractures with proximal displacement are relatively rare injuries to the rectus femoris due to the fact that its direct head tendons are attached to both the ilium and superior acetabular ridge, thus limiting how much displacement may occur at an AIIS avulsion site. When dealing with such cases, MRI may help identify swelling around an AIIS fracture site as well as determine whether bone fragments have dislocated.
Indirect head avulsions are less frequently experienced but still a significant source of quadriceps muscle injuries, typically occurring during sports that involve hip and knee extension, such as football and rugby. Due to its high percentage of fast-twitch fibers subjected to strong eccentric contractions during these activities, this injury type poses particular danger.
Indirect head avulsions should only be diagnosed by an experienced clinician. Common symptoms of indirect head avulsions include quadriceps tendon pain and restricted range of motion in the knee joint. Muscle strain injuries require prompt and aggressive rehabilitation to prevent future recurrence, which could result in functional limitations in both hips and knees. An MRI scan is used to confirm its diagnosis. MRI provides the optimal evaluation of injury severity, location and extent. Furthermore, it helps determine the degree of tensor fascia lata thickness as well as any fat pad enlargement present. MRI imaging can also assist in the assessment of potential musculotendinous junction (MTC) tears or tendon sheath tethering injuries at the site of an avulsion injury, and evaluate the presence of hip flexion contractures or osteophyte formation at this location. MRI can detect an enlargement in the quadriceps fat-pad on the prepatellar surface, while imaging of the rectus femoris typically uses T1-weighted sequence. A T2-weighted gradient echo sequence may also be added in order to distinguish it more clearly from surrounding soft tissues.
FAQs about Rectus Femoris Muscle and Injuries
Q1: What is the rectus femoris muscle, and what is its primary function?
A1: The rectus femoris is one of the quadriceps muscles situated within the knee joint. It acts to flex the hip while simultaneously extending it.
Q2: Where does the rectus femoris muscle originate and attach?
A2: It arises from the anterior inferior iliac spine and ilium above the acetabulum and attaches to the patella via the quadriceps tendon.
Q3: What are the components of the rectus femoris muscle, and how are they identified?
A3: The rectus femoris is divided into direct head and indirect head sections. Mild lesions on axial T1-weighted images typically display as bands of edema at their interface.
Q4: What is the function of the Direct Head of the rectus femoris?
A4: The direct head extends the knee joint and originates at the anterior inferior iliac spine and ilium. It attaches to the patella via the quadriceps femoris tendon.
Q5: What is “degloving” in the context of rectus femoris muscle injuries?
A5: “Degloving” is a type of quadriceps muscle injury where muscular bellies dissociate from one direct head, leading to functional limitations in hip flexion and loss of function in extending the knee joint.
Q6: How rare are anterior inferior iliac spine (AIIS) avulsion fractures, and what role does MRI play in their diagnosis?
A6: AIIS avulsion fractures with proximal displacement are relatively rare due to the tendon attachments. MRI can help identify swelling and determine if bone fragments have dislocated.
Q7: What are indirect head avulsions, and how are they typically experienced?
A7: Indirect head avulsions are less frequent but significant quadriceps muscle injuries, often occurring during sports involving hip and knee extension, such as football and rugby.
Q8: How are indirect head avulsions diagnosed, and what are common symptoms?
A8: Indirect head avulsions should be diagnosed by an experienced clinician. Common symptoms include quadriceps tendon pain and restricted knee joint motion.
Q9: Why is prompt rehabilitation essential for muscle strain injuries, and how is it done?
A9: Quick and aggressive rehabilitation is crucial to prevent future recurrence, which could result in functional limitations. MRI scans are used for diagnosis and evaluation of injury severity.
Q10: What role does MRI play in diagnosing and evaluating rectus femoris injuries?
A10: MRI provides optimal evaluation of injury severity, location, and extent. It helps determine tensor fascia lata thickness, musculotendinous junction tears, and assesses the presence of hip flexion contractures or osteophyte formation.
