Semimembranosus tendinopathy: one cause of chronic posteromedial knee pain

Is Dextrose Prolotherapy More Effective Than Steroids in the Treatment of Distal Semimembranous Tendinopathy?

OBJECTIVE

Distal semimembranous (SM) tendinopathy is one of the rare causes of posteromedial knee pain. Steroid injections are included in the treatment of resistant cases. The effectiveness of dextrose prolotherapy is not fully known. This study aimed to investigate the effectiveness of dextrose prolotherapy in distal SM tendinopathy and to compare it with the effectiveness of steroid injections.

METHODOLOGY

 The study included 12 patients who received ultrasound-guided steroid injections and 13 patients who received dextrose prolotherapy treatment with the diagnosis of distal SM tendinopathy. The patient's visual analog scale (VAS) and International Knee Documentation Committee Subjective Knee Assessment (IKDC) scores were analyzed before the procedure, as well as one week and four weeks afterward.

RESULTS

 Pre-procedure VAS scores were similar in the dextrose and steroid groups (4.00 ± 0.70, 4.33 ± 0.88 P = 0.308), while they were significantly lower in the steroid group at week 1 (1.84 ± 0.55, 1.16 ± 0.93, P = 0.036). Fourth-week VAS scores were significantly lower in the dextrose group (0.61 ± 0.65, 1.33 ± 0.65, P = 0.011). IKDC scores were similar in the dextrose and steroid groups before the procedure (48.34 ± 6.01, 46.66 ± 3.34, P = 0.402). In the first week, it was observed to be similar in the dextrose and steroid groups (55.03 ± 8.52, 53.30 ± 1.56, P = 0.496) and higher in the dextrose group in the fourth week (62.50 ± 14.46, 53.13 ± 1.60, P = 0.036).

CONCLUSIONS

It was observed that both dextrose prolotherapy and steroid injections were effective in reducing pain and improving functionality in the treatment of distal SM tendinopathy. Steroid injections showed better results in the first week, while dextrose prolotherapy yielded better outcomes by the fourth week.

What Is New about the Semimembranosus Distal Tendon? Ultrasound, Anatomical, and Histological Study with Clinical and Therapeutic Application

The semimembranosus muscle inserts into several tendons that are associated with some pathologies. Although ultrasound is useful for studying, diagnosing, and managing these pathologies, the correct interpretation of any images requires a clear knowledge of the related anatomical structures and the inter-related functions. We studied 38 cryopreserved non-paired knees from adult anatomical specimens and 4 non-paired knees from 29 to 38-week-old fetuses. The semimembranosus muscle and its tendons were located, observed, and injected under ultrasound guidance. The macroscopic anatomy was studied using dissection and anatomical cuts and the tendons were analyzed histologically. Measurements of muscle were taken 10 cm from the medial epicondyle and just before the tendon divided. The ultrasound facilitated the identification of the different divisions of the tendon of semimembranosus muscle and the rotation of the muscle and tendon from medial to posterior. An anatomical study confirmed this rotation and revealed an average width, thickness, and diameter of 38.29 mm, 14.36 mm, and 112.64 mm, respectively. Important relationships were observed between the divisions of the main tendons and the medial collateral ligament, the posterior side of the knee and popliteus muscle. This information can help to explain knee pathologies and facilitate rehabilitation after surgery.

Distal semimembranosus tendinopathy: A narrative review

Distal semimembranosus tendinopathy is a relatively uncommon diagnosis that can be responsible for medial knee pain. The semimembranosus tendon inserts on the posteromedial knee and is surrounded by the semimembranosus bursa, with both the bursa and tendon potential sources of pain. Similar to other tendinopathies, semimembranosus tendinopathy often occurs with overuse of the musculotendinous unit and is commonly seen in runners. Diagnosis can be made clinically and may be substantiated with use of ultrasound or magnetic resonance imaging. Scant literature exists evaluating the efficacy of treatments for this condition. Consequently, best practice for treatment is inferred from other similar tendinopathies, clinical expertise, and smaller studies on semimembranosus tendinopathy. Extrapolating from other tendinopathies, rehabilitation should be the cornerstone of initial treatment, with focus on kinetic chain and gait abnormalities, hamstring strength and neuromuscular control, and progressive tendon loading. Recalcitrant cases with a coexisting bursopathy can be treated with an ultrasound-guided bursal corticosteroid injection. Future studies may help delineate the optimal treatment regimen for this relatively uncommon diagnosis.

A Rare Case of Juvenile Idiopathic Arthritis following a Ruptured Baker’s Cyst in a Toddler

A Baker's cyst is usually an incidental finding in adults being investigated for a joint arthropathy, and its rupture preceding the diagnosis of juvenile idiopathic arthritis (JIA) is rare in children. Here, we describe a case of a 4-year-old girl who presented to the Emergency Department with right calf pain, swelling, and no preceding history of trauma. MRI confirmed a ruptured Baker's cyst with inflammatory arthropathy alongside an extensive synovial proliferation throughout the knee joint with large joint effusions and associated soft tissue oedema tracking superiorly and inferiorly along the medial head of gastrocnemius and anteriorly along the tibia. Further investigations revealed bilateral uveitis consistent with a diagnosis of juvenile idiopathic arthritis.

Popeye sign of the semimembranosus

A 23-year-old amateur football player presented 9 months after acute onset of severe pain and a lump in the posterior right knee whilst lifting a heavy box. He had been unable to return to playing football or climbing the stairs. Clinically, a Baker's cyst was suspected. MRI scan, the imaging modality of choice, was essentially normal. A subsequent ultrasound (US) scan demonstrated abnormal dynamic bunching of the muscle fibres at the distal semimembranosus myotendinous junction on resisted isometric contraction, most likely due to a previous tear isolated to the distal myotendinous junction. The proximal biceps femoris tendon is the most commonly injured part of the hamstring. Distal semimembranosus tears are far less common. Semimembranosus tendinopathy is an uncommon cause of chronic knee pain that is probably underdiagnosed and inadequately treated. In this case, the distal semimembranosus injury was occult on MRI because the features were only apparent with dynamic imaging, something that is not routinely part of musculoskeletal MRI protocols, whereas real-time imaging is easily performed with US. MRI is thought to be more sensitive than US for follow-up imaging of healing hamstring injuries; however, this case highlights the usefulness of dynamic imaging of muscle injuries with US. We propose that the abnormal dynamic muscle bulge on the US image would be aptly described as a "Popeye sign," which, to our knowledge, has not previously been reported in any other anatomical location than the long head of the biceps brachii in the published literature.