Proximal gastrocnemius tendon pathology – radsource gas estimator


The sagittal proton density-weighted fat-suppressed MRI images through the medial aspect of the knee demonstrate intramuscular edema at the anteromedial aspect of the medial gastrocnemius (arrow), without intramuscular tear or hematoma. gas constant for air In addition, there is abnormality of the medial gastrocnemius tendon, with intratendinous high signal (short arrow, 2b), and focal surface fraying and contour abnormality (arrowheads). There is also femoral bone marrow edema deep to the tendon insertion (asterisk). Fluid is present in the gastrocnemius bursa (curved arrow, 2a), located anterior to the myotendinous region.

Abnormalities involving the medial and lateral gastrocnemius tendons are often not considered among the many possible causes of knee pain. The medial gastrocnemius is rarely affected in traumatic injuries to the knee, and symptomatic chronic degenerative changes are also relatively uncommon. However, case reports in the literature 1,2, describe gastrocnemius tendon degenerative interstitial, longitudinal or partial-thickness tearing, and note that such abnormalities may cause clinical symptoms mimicking symptoms from more common lesions such as meniscal tears or collateral ligament strains. The medial and lateral gastrocnemius tendons proximal myotendinous regions are included in the field-of-view of knee MRI exams. Familiarity with the normal gastrocnemius tendon MRI features, as well as the spectrum of MRI findings with different types of pathology that may involve these structures is relevant for accurate interpretation of knee MRI. Anatomy and Function

The medial and lateral gastrocnemius tendons together with the soleus muscle form the calf. The gastrocnemius muscles extend half-way down the lower leg, distally contributing to the Achilles tendon. The gastrocnemius muscles but not the soleus cross the knee joint, and they all distally cross the tibiotalar joint (and the subtalar joint as well). electricity facts history Innervation is by the tibial nerve. Vascular supply to the gastrocnemius muscles is by stout short branches from the adjacent popliteal artery and vein; detailed studies of the venous vascular configuration has demonstrated 4 main patterns, with 2 to 12 branches per muscle head 3. electricity n and l The proximal tendons of the gastrocnemius muscles originate at the medial and lateral femoral epicondylar regions; the medial tendon is thicker along its medial margin and closer to midline contain small amounts of interspersed fat.

A 3D representation of the popliteal fossa with partial resection of the semimembranosus (SM), gracilis (G), and semitendinosus (ST) musculotendinous junctions demonstrates the origin of the medial head of the gastrocnemius muscle (MH) with medial tendinous and muscular lateral portions, arising just posterior to the adductor magnus tendon (AM) insertion. The plantaris (P), lateral head of the gastrocnemius muscle (LH), and biceps femoris (BF), and sartorius (S) muscles are also labeled. The medial gastrocnemius bursa and semimembranosus bursa are indicated by asterisks.

The gastrocnemius bursa is located deep to the tendon in the proximal myotendinous region, and usually communicates with the semimembranosus bursa. Fluid in the bursa is frequent when there is gastrocnemius tendinopathy, but is non-specific as it also occurs with internal derangement of the knee joint and multiple other pathologies. When the gastrocnemius-semimembranosus bursa is distended, this is termed a Baker’s cyst, frequently communicating with the knee joint through a 15-20 mm slit between the two, thought to occur at a region of frequent capsular insufficiency, and sometimes with a one-way valve function leading to continuous filling of the cyst 4.

The main gastrocnemius muscle function is plantar flexion of the foot, but it also provides flexion of the non-weight-bearing knee, and acts as an agonist for the PCL. The gastrocnemius muscles have a higher proportion of fast twitch fibers than the soleus, reflecting their function in jumping and running, while the soleus, with a higher proportion of slow twitch fibers, mainly functions in walking and postural control. In addition, all the calf muscles have a role as a venous pump for the lower limb (the “calf muscle pump” function) 5.

Gastrocnemius tendon degeneration may result from prior gastrocnemius injury, chronic overuse, or underlying posteromedial or posterolateral knee joint instability. electricity will not generally cause Gastrocnemius tendinosis may progress to an interstitial tear, longitudinal split tear, partial tear, or very rarely a complete tear. Clinical symptoms usually develop gradually and may include local pain and tenderness, as well as swelling at the posteromedial or posterolateral knee and proximal lower leg, weakness, and limited range of motion. MRI evaluation Normal MRI anatomy

The proximal tendons of the gastrocnemius muscles are flat, and originate at the medial and lateral femoral epicondylar regions in a linear fashion towards midline, slightly proximal to the condylar articular margin. At the medial gastrocnemius tendon origin, there are 2 features of importance for MRI evaluation: (1) the origin extends from the epicondyle (about 1 cm distal to the adductor magnus tendon insertion) and runs obliquely so that it is more proximal near the femoral posterior midline, and (2) the tendon is thicker and more defined medially, and more attenuated closer to femoral midline (4a,4b).

A series of sagittal proton density-weighted images with fat saturation proceeding from medial to lateral and an axial proton density-weighted image with fat suppression (10a) demonstrate a partial insertional tear of the medial gastrocnemius tendon (arrows), with a longitudinal interstitial tendon tear seen as increased signal within the diffusely thickened tendon (arrowheads). Edema within fat deep to the attenuated fibers towards the midline (asterisk) is apparent. Associated medial pericapsular edema is also seen (short arrows, 10b).

A complete gastrocnemius tendon tear is quite rare in the setting of chronic tendinosis, and is also rare in cases of acute knee trauma. youtube gas monkey Fluid in the gastrocnemius bursa, located deep to the proximal tendon and immediately superficial to the posteromedial joint capsule, is associated with medial gastrocnemius tendon pathology but is non-specific as it is commonly found with many types of knee joint pathology.

It is important to consider the “magic angle” MRI artifact as a common cause of intratendinous intermediate signal within especially the medial gastrocnemius tendon. This artifact can be seen on short TE images (such as T1s) in regions where a tendon is oriented at 55 degrees to the main magnetic field, such as the medial gastrocnemius tendon about 2 cm distal to the femoral origin; correlation with T2 weighted images will help to exclude focal pathology (11a).

In calcium pyrophosphate crystal deposition disease (CPPD), in addition to chondrocalcinosis there is often calcification involving tendons. gas 4 weeks pregnant Around the knee, calcification of the medial gastrocnemius tendon has been reported 15. Acute gastrocnemius avulsion fracture has rarely been described in the literature, and would result from an acute injury; if there is significant displacement, surgery may be indicated.

The fabella is a small sesamoid located within the lateral gastrocnemius at the level of the lateral femoral condyle. It is present in 10-20% of the population, and is usually ossified with a small facet of hyaline cartilage towards the joint, or may be fully cartilaginous (13a). It might show participation in osteoarthritis of the knee joint, with cartilage loss, subarticular marrow edema, and marginal osteophytes causing overall enlargement of the fabella which occasionally leads to localized pain related to impingement during knee flexion. grade 6 science electricity unit test Fabellar fracture 9 or displacement 10 are rare causes of acute posterolateral knee pain, while localized discomfort labeled “fabellar syndrome” has been described as a cause of insidious chronic symptoms, accessible to manual fabellar mobilization therapy 16.

A dissecting Baker’s cyst 11 may present with tender fullness at the posteromedial aspect of the knee just below the joint; these lesions represent rare instances where a Baker’s cyst enters through the muscle fascia and is present often both outside and within a muscle compartment. Normally a Baker’s cyst enlarges in the direction of least resistance, most commonly along the medial gastrocnemius muscle belly distally. If a focal fascial defect occurs, or at a pre-existing weak region, the Baker’s cyst can enter the muscle compartment. As with other Baker’s cysts, treatment of the underlying cause of the joint effusion is indicated, as the cysts are manifestations of fluid decompressing out of the joint due to higher intra-articular pressure.

Venous thrombosis of the lower leg most commonly involves the deep vessels and often also the calf muscle veins, and is often thought to originate at these muscle veins. A small percentage of cases demonstrate thrombosis limited to the calf muscle veins; these cases may present with symptoms similar to post-exertion calf muscle pain, and may be clinically mistaken for a muscle strain 13.

Other abnormalities involving the gastrocnemius tendons or proximal myotendinous region include an accessory gastrocnemius muscle belly, post-surgical changes related to the use of the gastrocnemius for a vascular flap at a soft tissue defect around the knee, the rare use of a gastrocnemius silicone implant for cosmetic procedures, and soft tissue masses such as a lipoma.

Accessory gastrocnemius muscle bellies (“third head of the gastrocnemius”) have been associated with vascular claudication due to extrinsic vascular functional compression or entrapment 17, though the majority of these congenital lesions are asymptomatic (Figure 14). MR angiography has proven useful for evaluation of suspected popliteal artery entrapment syndrome 18.

Sagittal T1-weighted (16a) and axial proton density-weighted fat-suppressed (16b) images demonstrate an asymptomatic posteromedial intermuscular lipoma (asterisk) ventral to the medial gastrocnemius muscle and tendon (MG) in a 25 year-old male runner who underwent MR imaging after a running injury. The semimembranosus tendon (SM) is also indicated.

Degenerative proximal tendinosis at the medial or lateral gastrocnemius may develop into interstitial or partial-thickness tendon tearing. These abnormalities may co-exist with the more common causes of knee pain such as meniscal tear or osteoarthritis, or may be the only abnormality demonstrated on an MRI examination of the knee. Gastrocnemius tendons may demonstrate MRI signal changes attributed to magic angle artifact, but when there is high T2 signal within the tendon, contour change or defect, and associated edema at bone marrow and soft tissues, gastrocnemius tendinopathy can be diagnosed on knee MRI exams, and may well be contributing to the patient’s clinical symptoms. References