Introduction:
Semimembranosus tendinopathy is an inflammation of the semimembranosus tendon's insertion. This could be causing activity-related posteromedial knee pain. One of the hamstring muscles in the posteromedial (at the back, towards the middle of the body) aspect is the semimembranosus. The semimembranosus muscle's primary role is in the flexion (bending) and internal rotation (twisting movement) of the knee joint. Moreover, it stabilizes the pelvis and helps the hip joint extend. The incidence is higher in the population of athletes and older patients.
What Is the Anatomy of the Semimembranosus Tendon?
The semimembranosus muscle has its origin at the lateral aspect of the ischial tuberosity (sit bones), and it travels posteromedially down the thigh before inserting at the posteromedial face of the knee. Just above the knee joint, the muscle belly forms a large, rounded tendon that travels medially to the medial head of the gastrocnemius (calf muscle) but laterally to the shorter semitendinosus tendon. The semimembranosus muscle is primarily responsible for the flexion and internal rotation of the knee joint. Moreover, it causes the hip joint to extend and stabilizes the pelvis. The medial tibial plateau (bony surface in the lower leg), the MCL (medial collateral ligament, - ligament of the knee), and the semitendinosus (thigh muscle) are all separated from the distal parts of the distal SM tendon by a U-shaped bursa (a fluid-filled sac). Friction and repetitive eccentric tendon loading can cause bursitis and degenerative alterations to the tendon and its insertions.
What Is the Mechanism of Injury of the Semimembranosus Tendon?
The muscle belly creates a thick, rounded tendon distally that passes medially to the medial head of the gastrocnemius (calf muscle) but laterally to the smaller semitendinosus tendon just above the knee joint. The muscle belly ends just above the knee joint. Semimembranosus tendinopathy typically appears in the distal tendon, at mirrored insertions, or in the main (direct) head. The semimembranosus tendon is exposed to increased friction from the nearby joint capsule, medial femoral condyle (a bony eminence present in the knee), medial tibial plateau, and semitendinosus tendon during repetitive knee flexion. In addition to irritating the bursa, friction and repeated eccentric tendon loading can cause degenerative changes in the tendon and its insertions. Typical mechanisms of injury include:
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Stress imposed on the tendon as a result of an abrupt increase in training volume, frequency, or duration and the body compensating for other lower extremity problems (meniscus tear). Activities that require repetitive and demanding use of the knee and hip. Activities such as distance running, triathlons, race walking, weightlifting, or climbing, as well as running down hills, increase risk.
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Inadequate flexibility and strength.
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Incorrect warm-up before activity, flat feet, and unnatural knee alignment (knock knees or bow-legged).
What Are the Causes of Semimembranosus Tendinopathy?
Semimembranosus tendinopathy is usually brought on by:
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An underlying problem in long-distance runners or a secondary overuse injury resulting from an underlying knee deformity.
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Chondromalacia patellae (the deterioration and softening of the cartilage on the underside of the kneecap) and degenerative medial meniscal tears are two examples of additional knee pathology that frequently coexists and may mislead the clinical presentation or perhaps be the cause.
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Due to nearby osteophytes (bony growth) on the joint line, elderly people with osteoarthritis (joint disease) may experience semimembranosus tendinopathy at the insertion of the anterior reflected tendon.
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Concomitant pes anserine tendonitis (inflammation of the bursa, a fluid-filled sac in the knee) is another common condition affecting these patients. Components of total knee replacements may also contribute to secondary semimembranosus tendinopathy.
A strong preference for women has been reported by some authors. This might be explained by higher valgus stress and the Q angle (the angle formed between the thigh muscle and kneecap) that women have. Similar to this, increased valgus tension may result from excessive foot pronation (the manner in which the foot rolls inward to distribute impact while landing). Both circumstances could lead to more friction between the SM tendon and the medial femoral condyle, but no studies have looked at any of these aspects as potential risk factors for semimembranosus tendinopathy.
What Are the Clinical Characteristics of Semimembranosus Tendinopathy?
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A subtle, developing knee soreness in the posteromedial region.
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Palpable tenderness.
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During the direct implantation, pain is typically restricted to the posteromedial knee. Pain may travel proximally up the posteromedial thigh or distantly to the medial calf.
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Activities that significantly activate the hamstrings, such as running, cycling, descending stairs, or abrupt deep knee flexion, cause symptoms to worsen.
What Are the Methods Used to Diagnose Semimembranosus Tendinopathy?
The diagnosis of tendinopathy, a syndrome characterized by tendon pain and thickness, is mostly based on the patient's medical history and physical examination.
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Imaging Methods: The preferred techniques for seeing the hamstring tendon complex are magnetic resonance imaging (MRI) and ultrasonography (US). Better contrast between soft tissue is an advantage of MRI. It is more sensitive than the US in identifying proximal hamstring tendon tendinopathy and peritendinous edema. Imaging is used to determine the severity of the injury and establish the existence of hamstring tendon pathology. A bone scan can support a diagnosis as well. The proximal tibia's posteromedial portion exhibits higher tracer uptake there.
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Physical Examination: When the semimembranosus tendon is palpated near or slightly more proximally to its tibial insertion site (or sites), there is soreness. The semimembranosus tendon can become more visible for easier probing when the knee is flexed against resistance at 90 degrees. The discomfort might be localized through passive internal tibial rotation of a knee bent at 90 degrees. Due to nearby structures impinging on the afflicted tendon and insertion during passive deep flexion of the knee, this may also make the discomfort worse. The anatomy of the hip, ankle, and foot should be examined for biomechanical traits that might be associated with semimembranosus tendon overuse.
How Is Semimembranosus Tendinopathy Managed?
Due to the scant scientific evidence supporting the efficacy of therapies being employed, there is still no widespread agreement on the optimal conservative care of semimembranosus tendinopathy.
The majority of conservative treatment options for semimembranosus tendinopathy are similar to those used for other tendinopathies, including relative rest, ice, and nonsteroidal anti-inflammatory drugs (NSAIDs), reduction or suspension of sports participation, soft tissue mobilization, physiotherapy, ongoing home exercise programs with a progressive hamstring strengthening focus. Normal healing times range from one to three months. Patients with chronic tendinopathy can benefit from shockwave therapy as it is secure and reliable.
Conclusion:
Because most practitioners are unaware of SMT, it may be more widespread than what is suggested by the medical literature. In ideal circumstances, early successful conservative therapy or surgical management of concurrent underlying pathology will follow a detailed history, thorough examination, and imaging scans that identify the condition early.
