Popliteal (Baker’s) Cyst

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

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.

Normal Anatomy The Gastrocnemius-Semimembranosus Bursa:

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

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

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°

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.

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

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.

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

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.

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.

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

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.

Surgical - Management Cyst aspiration Cyst drainage and injection of corticosteroid into the cyst space Arthroscopy: resection of the valvular opening, debridement http://www.youtube.com/watch?v=nCcQ-U3ajfQ