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We present a case of medial head of gastrocnemius tendon tear. The type of injury widely reported in the literature is tear of the medial head of gastrocnemius muscle or ‘tennis leg’. We previously reported an isolated partial tear and longitudinal split of the tendon to the medial head of gastrocnemius at its musculotendinous junction. The case we now present has notable differences; the tear was interstitial and at the proximal (femoral attachment) part of the tendon, the patient’s symptoms and clinical examination suggested a medial meniscus tear, and magnetic resonance imaging demonstrated bone oedema at the tendon insertion site indicating a traction injury. Both cases suggest that isolated tear of the medial head of the gastrocnemius tendon may have a variety of presentations and appearances and should be considered in the differential diagnosis of tennis leg as well as medial meniscus tear.
Tear of the gastrocnemius muscle is the injury most reported in the literature and referred to as ‘tennis leg’.1–4 We previously reported a case of medial head of gastrocnemius tendon tear where the patient presented with an asymptomatic lump in the calf, and imaging demonstrated a longitudinal split in the distal portion of the tendon.5 The case we present here is also of isolated partial tear of the medial head of gastrocnemius tendon, but with several notable differences. The patient presented with a history of pain and swelling posterior medial to the knee joint and was suspected of having a medial meniscus tear. Magnetic resonance imaging (MRI) demonstrated a partial interstitial tear of the proximal portion (close to the femoral attachment) of the tendon. There was focal marrow oedema within the posterior superior aspect of the medial femoral condyle, indicating a traction injury of the tendon at the insertion site. The differences between the two cases suggests that tears of the medial head of the gastrocnemius tendon can vary in terms of site of tear, clinical presentation and findings at imaging.
A 46-year-old female massage therapist was reviewed in the orthopaedic outpatients’ clinic complaining of 3–4 months of left knee pain and medial side discomfort on flexion. The pain came on after she had been kneeling for long periods of time or sitting in a chair. She could not recall any previous injury, although she had been on a skiing trip 3 months before the onset of symptoms. The knee did not lock or give way. She had no other clinical complaints or illnesses and was not on any medication. On examination the patient had a normal gait. There was no effusion of the knee but there was restricted flexion of the affected left knee compared to the right. The range of movement of the left knee was 0–120°. There was posterior medial joint line tenderness. There was no instability.
Plain radiographs were normal (fig 1). MRI scans (figs 2–12) demonstrated oedema and swelling of the proximal portion of the tendon to the medial head of gastrocnemius, with poorly defined tendon morphology, indicating a partial interstitial tear of the tendon. There was also partial avulsion of the tendon from the femoral insertion site and oedema within the surrounding soft tissues. In addition, a small focus of subcortical bone oedema was present in the posterior medial aspect of the medial femoral condyle at the tendinous insertion. This indicated a traction injury. Ultrasound (figs 13–17) demonstrated a proximal interstitial partial tear of the tendon to the medial head of gastrocnemius and partial avulsion from its insertion into the femur. Assessment of the tendon, however, was more difficult with ultrasound due to anisotropy. Anisotropy in ultrasound occurs when the structure being imaged is at an angle other than 90° to the incident ultrasound beam emitted from the probe. The tendon to the medial head of the gastrocnemius takes a curvilinear direction as it courses from the muscle to the medial femoral condylar attachment (site of tear in this case). The appearance of anechoic sections of the tendon as a result of anisotropy were an artefact that suggested complete tendon disruption. It therefore relies on the skill of the ultrasound operator to be aware of this pitfall and take corrective measures such as angling the probe to be able to see the tendon.
The patient was managed conservatively with no deterioration of symptoms at 4 months follow-up.
At 4 months there has been no deterioration in symptoms.
Injuries reported in the literature, often referred to as ‘tennis leg’, involve tears of the gastrocnemius muscle rather than the tendon.1–4 The case we now present demonstrated an interstitial partial tear of the tendon and partial avulsion form its insertion site. This case shows a different type and appearance of a partial tear of the medial head of gastrocnemius tendon compared to the case we previously reported,5 which showed a longitudinal split in the distal gastrocnemius tendon at the musculotendinous junction. It had presented as a painless lump with no clear history of trauma. The current case also had an unclear history of trauma and presented with symptoms suggestive of medial meniscus tear. It was shown at imaging to be a proximal tear of the tendon close to the insertion site into the posterior aspect of the femoral condyle. The tear was interstitial rather than a discreet split in the tendon. The two different patterns of tear and different sites suggest therefore that isolated tears of the medial head of the gastrocnemius tendon may take on various forms and are likely to be underreported. Other injuries to consider in the differential of posterior medial knee pathology include avulsion fractures of the medial head of gastrocnemius muscle.
Machara et al reported the first recorded case of avulsion fracture of the medial head of gastrocnemius muscle.6 This followed an acute skiing injury. Plain radiographs revealed a bone fragment in the popliteal fossa. MRI revealed no tear to the gastrocnemius muscle, but it had avulsed from its insertion along with a bone fracture avulsion fragment.6 Unlike the case reported by Machara et al, the abnormality in our case was confined only to the tendon which demonstrated partial tear proximally. The muscle was normal. As the patient did not present with a clear history of trauma, the other differential diagnosis we should have considered is calcifying tendonitis of the gastrocnemius tendon. Iguchi et al7 reported three cases of isolated non-traumatic calcifying tendonitis of the medial head of gastrocnemius tendon presenting with pain in the posterior medial aspect of the knee.
Of important consideration also, and highlighted by our two cases, is the role of imaging. During assessment of the tendon with ultrasound in the case we present here, we encountered difficulties due to anisotropy. Anisotropy in ultrasound happens when the structure being imaged is at an angle other than 90° to the incident ultrasound beam emitted from the probe. Anisotropy occurred because the tendon to the medial head of the gastrocnemius takes a curvilinear direction as it courses from the muscle to the medial femoral condylar attachment. It therefore depends on the skill of the ultrasound operator to be aware of this and take corrective measures such as angling the probe to be able to see the tendon. The appearance of anechoic sections of the tendon as a result of anisotropy were an artefact that suggested complete tendon disruption. MRI did not suffer from this artefact and was therefore the imaging modality of choice in this case. In the previous case,5 however, the tear being in the straight (distal, musculotendinous) portion of the tendon, anisotropic artefact did not occur and was therefore not an issue. Hence ultrasound was an excellent imaging tool for the assessment of that portion of the tendon. The case we present here also had bone abnormalities which would not have been seen if ultrasound alone had been done. MRI demonstrated the subchondral bone oedema.
To conclude, isolated medial head of gastrocnemius tendon tears may present in various forms and are likely to be under-reported. In order to identify these injuries, diagnostic imaging modalities should be carefully considered and appropriately selected in order to show all relevant abnormalities. Both MRI and ultrasound have advantages and disadvantages depending on the specific abnormalities to be demonstrated.
Competing interests: None.
Patient consent: Patient/guardian consent was obtained for publication.