Anatomy
Lower Limb
A 23 year old tennis player sustains an injury to her leg and is complaining of weakness of dorsiflexion and inversion of her foot. Which of the following muscles is most likely affected:
Answer:
The tibialis anterior acts to produce dorsiflexion and inversion of the foot. The tibialis posterior assists in inversion, but acts to produce plantarflexion. The fibularis tertius assists in dorsiflexion but also assists with eversion of the foot. The fibularis longus and fibularis brevis predominantly act to produce eversion of the foot.Anterior Leg Muscles
Anatomy / Lower Limb / Anterior Leg
Last Updated: 11th April 2019
The anterior compartment of the leg is made up of four muscles: the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus and the fibularis tertius which collectively dorsiflex the foot at the ankle joint.
Table: Function and Innervation of the Anterior Leg Muscles
| Muscle | Function | Innervation |
|---|---|---|
| Tibialis anterior | Dorsiflexion and inversion of foot, support of medial arch of foot | Deep fibular nerve |
| Extensor hallucis longus | Extension of great toe and dorsiflexion of foot | Deep fibular nerve |
| Extensor digitorum longus | Extension of lateral four toes and dorsiflexion of foot | Deep fibular nerve |
| Fibularis tertius | Dorsiflexion and eversion of foot | Deep fibular nerve |
Innervation
These muscles are all innervated by the deep fibular nerve.
Function
The tibialis anterior dorsiflexes the foot at the ankle, inverts the foot at the intertarsal joints and provides dynamic support of the medial arch of the foot while walking.
The extensor hallucis longus extends the great toe and dorsiflexes the foot at the ankle joint.
The extensor digitorum longus extends the lateral four toes and dorsiflexes the foot at the ankle.
The fibularis tertius, sometimes considered part of the extensor digitorum longus, assists in dorsiflexion and eversion of the foot.
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2017/01/Anterior-Leg.jpg)
Anterior Leg Muscles: Tibialis anterior (red), Extensor hallucis longus (green), Extensor digitorum longus (blue), Fibularis tertius (yellow). (Image modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
