International Journal of Sport, Exercise and Health Research 2026; 10(1): 18-26 ;   DOI:10.31254/sportmed.10104

Research Article

Characterisation of Calf Strain and its healing through Clinical and Functional Assessment and Ultrasonography in the Active Population

Jason Kok Kiong Chia¹ , Nicholas Jiajie Leong¹ , Xiaoe Zhang²

Jason Kok Kiong Chia,Nicholas Jiajie Leong,Xiaoe Zhang

1. Department of Orthopaedic Surgery, Tan Tock Seng Hospital, Tan Tock Seng, Singapore
2. Clinical Research & Innovation Office, Tan Tock Seng Hospital, Tan Tock Seng, Singapore

*Author to whom correspondence should be addressed.

Received: 28th March, 2026 / Revised: 1st January, 1970 / Accepted: 8th August, 2024 / Published : 24th August, 2026

Abstract

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Background: Calf muscle strain, particularly at the distal musculotendinous junction of the medial gastrocnemius and soleus aponeurosis (“tennis leg”), is a common sports injury associated with pain, disability, and risk of recurrence. Despite its high incidence, prospective data describing its clinical course and correlation with functional and ultrasonographic recovery are limited. This study characterises the clinical features, functional recovery and ultrasonographic healing of calf strain in physically active adults with the single heel raise being a clinically useful test to assess patients’ function. Methods: Thirty physically active patients aged 21–65 years presenting within six weeks of acute calf pain were prospectively recruited from a sports medicine clinic. Diagnosis was confirmed by history, clinical examination, and ultrasonography. Exclusion criteria included chronic calf pain, other lower limb pathologies, or absence of a visible muscle defect. Participants underwent serial clinical and ultrasonographic evaluation at baseline, 3 weeks, 6–12 weeks, and 5–6 months. Pain intensity (visual analogue scale, VAS), swelling, tenderness, induration, and single heel raise ability were assessed at each visit. Functional status was evaluated using the Foot Function Index (FFI) and Lower Extremity Functional Scale (LEFS). Ultrasonographic measurements of defect length, width, and depth were recorded. Statistical analysis employed linear mixed-effects models and Kaplan–Meier estimates to assess associations between functional recovery and imaging findings. Results: Twenty-eight participants (80% male, mean age 48.3 ± 13.1 years) completed the study. Most injuries (93.3%) involved the distal musculotendinous junction between the medial gastrocnemius and soleus aponeurosis. At presentation, all patients reported acute pain (mean VAS 4.4) and a limp, 93.3% had swelling, and 63.3% had bruising. Mean initial ultrasound defect size was 90.2 × 37.2 × 11.3 mm. Reparative tissue was identified in 80% of cases at the first follow-up. Median time to symptom recovery (VAS < 3) was 5 weeks, while median time to primary union on ultrasound was 10 weeks (p = 0.01). Functional scores improved significantly during follow-up: mean FFI decreased from 45.6 to 7.0, and LEFS increased from 41.3 to 73.3. Patients achieving symmetrical single heel raise on clinical examination demonstrated superior function (LEFS 68.2 vs 50.7, p = 0.002; FFI 10.0 vs 35.2, p = 0.0005). No significant association was observed between functional outcomes and calf circumference or induration length. Conclusion: Calf strain primarily affects the medial gastrocnemius–soleus junction and demonstrates good recovery with conservative management. Clinical symptoms resolve before complete ultrasonographic healing, with median recovery times of five and ten weeks, respectively. The single heel raise test is a useful, simple indicator of functional improvement. While clinical improvement supports safe return to daily activities, ultrasonography remains valuable in confirming primary union prior to resuming high-intensity or explosive sports. This study provides prospective evidence correlating clinical, functional, and imaging recovery patterns to guide rehabilitation and return-to-play decisions.

Keywords

Tennis leg, Gastrocnemius, Single heel raise, Ultrasonography, Muscle strains, Return to sport

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