A popliteal cyst (Baker’s cyst) is a synovial outpouching that arises from the posteromedial aspect of the knee joint. The synovial membrane of the knee joint outpouches between the medial head of the gastrocnemius and the semimembranosus tendon to lie medially within the popliteal fossa. Occasionally it tracks inferiorly to lie in and around the tendons that form the pes anserinus (sartorius, gracilis, and semitendinosus).
An arterial adventitial cyst is an uncommon cystic structure that arises from the wall of the artery.
An ultrasound investigation was carried out.
Using real-time ultrasound the dimensions of the popliteal aneurysm were characterized and the flow in the vessels was demonstrated. Furthermore, a popliteal cyst and adventitial cyst were completely excluded.
The patient underwent a surgical excision and graft interposition and has made an uneventful recovery.
A young long-distance runner came to her physician with acute swelling around the lateral aspect of her ankle. This injury occurred directly after accidentally running into a pothole in the pavement.
A fractured ankle was suspected.
Plain anteroposterior and lateral radiographs of the ankle revealed no evidence of any bone injury to account for the patient’s soft tissue swelling.
The patient was given a pair of crutches and analgesics and told to rest. A diagnosis of a simple sprain was made.
Over the ensuing weeks the swelling and edema within the soft tissue of the ankle decreased and the patient began to run, but noted that the ankle kept “giving way.” She went to an orthopedic surgeon for further assessment.
There was a positive anterior drawer test of the ankle joint.
At this stage it is important to review the mechanism of injury. Typically when running on a hard surface the final phase of push-off involves supination of the foot. If the foot is caught in a pothole or divot, this supinating maneuver continues and inverts the ankle joint in plantarflexion. This puts significant strain on the lateral ligament complex and, given the appropriate circumstances, disruption (in order) of the ligament structures occurs from anterior to posterior. First, the anterior talofibular ligament is disrupted, followed by the calcaneofibular ligament, and then the posterior talofibular ligament. As each of these ligaments is disrupted, the severity of the soft tissue injury is significantly enhanced and the chance of permanent ankle instability is increased.
On examination any positive anterior drawer test of the ankle (4–5 mm compared to the opposite side) suggests an injury to the anterior talofibular ligament.
The anterior talofibular ligament can be assessed by placing the foot in marked plantarflexion. If there is over 10° of difference between the affected foot and nonaffected foot, an anterior talofibular ligament disruption is suspected.
It is extremely rare for all three ligaments to be disrupted, and if so there are usually other significant ankle injuries.
Magnetic resonance imaging (MRI) was carried out to assess ligament damage.
MRI is excellent for demonstrating the medial and lateral ligament complexes of the ankle as well as the soft tissues that support the bones of the posterior foot.
Unfortunately for this patient there was a tear of the anterior talofibular ligament (eFig. 6.145), which had to be repaired surgically.
670.e2 670.e1
In the clinic—cont’d
Table 6.1 Branches of the lumbosacral plexus associated with the lower limb—cont’d
Regional Anatomy • Deep Fascia and the Saphenous Opening
Fig. 6.73, cont’d
Surface Anatomy • Avoiding the Sciatic Nerve
Surface Anatomy • Identifying Structures Around the Knee
Surface Anatomy • Finding the Tarsal Tunnel—the Gateway to the Foot