Anatomy
Lower Limb
A 17 year old man has dislocated his left patella during a rugby match. Which of the following muscles should the physiotherapist focus on in rehabilitation to prevent recurrent dislocations:
Answer:
The patella typically dislocates in a lateral direction. The lower portion of the vastus medialis muscle on the medial thigh inserts upon the medial aspect of the patella and acts to draw the patella in a medial direction (especially in terminal extension). If the vastus medialis muscle is not strong enough, the patella is much more susceptible to dislocation.Patella
Anatomy / Lower Limb / Patellar Region
Last Updated: 10th April 2019
The patella is a sesamoid bone embedded in the quadriceps femoris tendon which sits in the trochlear groove of the anterior femur. The patella acts to magnify the force exerted by the quadriceps femoris and to redirect the quadriceps force as it undergoes normal lateral tracking during flexion.
The medial and lateral patellar retinaculum are formed primarily from fibres of the vastus medialis muscle, and the vastus lateralis muscle and iliotibial tract respectively, and attach the patella margins to surrounding fascia.
The quadriceps femoris tendon is continuous distally with the patellar ligament which is attached to the tibial tuberosity distally.
Patella. (Image by OpenStax College [CC BY 3.0 , via Wikimedia Commons)
Factors Preventing Lateral Patellar Draw
There are several structures that work together to keep the patella aligned and stabilised on the femur to prevent excessive lateral movement of the patella:
- The lateral femoral condyle on the lateral aspect of the trochlear groove is normally slightly higher than the medial aspect, providing a buttress to the patella on the lateral side.
- The vastus medialis muscle on the medial thigh acts to draw the patella in a medial direction. If the vastus medialis muscle is not strong enough, the patella is much more susceptible to dislocation.
- The medial patellofemoral ligament, extending from the medial aspect of the patella to the medial femoral condyle, provides a significant force (about 60%) against lateral displacement.
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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 |
