Anatomy
Lower Limb
A 67 year old man presents to the ED complaining of pain and swelling to the posterior knee. On examination you note a tender swelling in the popliteal fossa. The popliteal fossa is bordered superiorly by which of the following muscles:
Answer:
The popliteal fossa is bordered superomedially by the semimembranosus and superolaterally by the biceps femoris.Popliteal Fossa
Anatomy / Lower Limb / Popliteal Fossa and Knee
Last Updated: 10th April 2019
The popliteal fossa is a diamond-shaped space behind the knee joint.
Table: Anatomical Boundaries and Contents of the Popliteal Fossa
| Popliteal fossa | Structure(s) |
|---|---|
| Superomedial border | Semimembranosus |
| Superolateral border | Biceps femoris |
| Inferomedial border | Medial head of gastrocnemius |
| Inferolateral border | Lateral head of gastrocnemius and plantaris |
| Floor | Knee joint capsule and adjacent surfaces of femur and tibia and popliteus muscle |
| Roof | Deep fascia |
| Contents | Popliteal artery, popliteal vein, tibial nerve, common fibular nerve |
Anatomical boundaries
The popliteal fossa is bordered:
- superomedially by the semimembranosus
- superolaterally by the biceps femoris
- inferomedially by the medial head of the gastrocnemius
- inferolaterally by the lateral head of the gastrocnemius and plantaris
The floor of the fossa is formed by the capsule of the knee joint and adjacent surfaces of the femur and tibia, and more inferiorly by the popliteus muscle.
The roof is formed by deep fascia.
![Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2017/01/Popliteal-Fossa-3.png)
Anatomical Boundaries of Popliteal Fossa. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Contents
The major structures contained within the popliteal fossa are (from medial to lateral):
- the popliteal artery
- the popliteal vein
- the tibial nerve
- the common fibular nerve
The small saphenous vein ascends in the superficial fascia on the back of the leg to the knee where it penetrates the deep fascia and enters the popliteal fossa to drain into the popliteal vein. One other structure that passes through the roof of the fossa is the posterior cutaneous nerve of the thigh which descends through the thigh superficial to the hamstring muscles, passes through the roof of the popliteal fossa, and then continues inferiorly with the small saphenous vein to supply skin on the upper half of the posterior leg.
![Modified by FRCEM Success. Original by Henry Vandyke Carter [Public domain], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2017/01/Popliteal-Fossa.jpg)
Contents of Popliteal Fossa. (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 |
