1. Popliteal (Baker’s) Cyst

2. Normal Anatomy
The popliteal fossa is diamond shaped with four borders, formed by the muscles of the posterior compartment of the leg and thigh.

3. Normal Anatomy
The popliteal fossa is the main channel for neurovascular structures entering and leaving the leg.
The tibial nerve and common fibular nerve are the most superifical structures and the popliteal artery is the deepest.

4. Normal Anatomy
The Gastrocnemius-Semimembranosus Bursa:

5. Pathophysiology
“A benign swelling of the semimembranous bursa found behind the knee joint” O’Sullivan 2014.
Knee joint effusion communicates with posterior bursa through a valvular opening
Valve allows movement in one directions only – out of knee
Fluid collects in the bursa causing enlargement and bursitis
Often referred to as a popliteal cyst

6. Mechanism of Injury
Bakers’ cysts can be form by virtually any cause of joint swelling: arthritis, rheumatoid arthritis, joint effusion, meniscal tears, joint capsule herniation into the popliteal region

7. Classification Lindgren and Rauschning Criteria:
Grade 0, absence of swelling and pain, no limitation of range of motion;
Grade 1, light swelling and/or a sense of posterior tension after intense activity, minimal limitation of range of motion;
Grade 2, swelling and pain after normal activity, range of motion limitation less than 20°
Grade 3, swelling and pain even when resting, range of motion limitation more than 20°

8. Classification
Primary: No communication between the distension of the bursa and the knee joint with no associated knee derangement, majority seen in children.
Secondary: communicates freely with the bursa and the knee joint. Majority are secondary.

9. Associated Pathologies
Rheumatoid arthritis
Osteoarthritis
Gout
Meniscal injury.
DVT
Popliteal artery aneurysm

10. Subjective Age: Adult (if symptomatic), (50+ are more likely.)
Local pain at back of knee
Pain when extending knee
Posterior knee tightness on walking or activity
Reports Knee giving way or locking
Clicking of the knee
Knee stiffness
History of meniscal injury, ACL injury OA or RA
Rupture: intense knee/calf pain, swelling and redness.

11. Objective Palpable mass/swelling at the posterior knee joint line.
Reduced knee ROM
Pain at back of knee when squatting.

12. Special Tests
Fouchers’ sign: Knee in full extension and in 90 degrees flexion. Examiner places thumbs around anterior knee joint line and fingers into the fossa posteriorly. Mass may be palpated at extension and disappear on flexion to 45 degrees, whereas other masses may stay firm.

13. Further Investigation
Ultrasound or MRI
Ultrasound has been found to be a reliable, rapid, and highly sensitive technique of diagnosis.
5-18% prevalence rate by MRI
40-42% prevalence rate by ultrasound.
Useful for differential diagnosis.

14. Management Dependent on the cause
Surgical intervention may be required if intra articular pathology co-exists
Conservative intervention manages symptoms only

15. Conservative - Management
Swelling management
Massage
Ice
NSAID’s
Rest
For restricted ROM: Manual therapy such as joint mobilisations and home exercise programme of quadriceps and hamstring stretches.
For reduced strength: isometric knee strengthening exercises
Avoid high impact activities: substitute swimming or cycling.

16. Surgical - Management Cyst aspiration
Cyst drainage and injection of corticosteroid into the cyst space
Arthroscopy: resection of the valvular opening, debridement