Which tendons on the posterior knee that extend to the posterior thigh and calf can cause pain, a popping sensation, and palpable divots?

Posterior Knee Tendons with Pain, Pop, and Palpable Divots

Based on your clinical description of pain, popping sensation, and palpable divots in the posterior knee extending to the thigh and calf, you are most likely dealing with either medial hamstring tendons (semitendinosus and gracilis) or the lateral biceps femoris tendon, with gastrocnemius and semimembranosus tendons also being anatomically relevant structures in this region.

Key Anatomical Structures

The posterior knee contains several tendons that extend between the thigh and calf:

Medial Side:

• Semitendinosus tendon - extends from posterior thigh to medial tibia
• Gracilis tendon - extends from medial thigh to medial tibia
• Semimembranosus tendon - extends from posterior thigh to posterior medial tibia
• Medial gastrocnemius tendon - originates from posterior medial femoral condyle, extends to calf

Lateral Side:

• Biceps femoris tendon - extends from posterior thigh to fibular head
• Lateral gastrocnemius tendon - originates from posterior lateral femoral condyle, extends to calf
• Popliteus tendon - runs along posterolateral knee

Clinical Presentation and Diagnosis

Snapping Medial Hamstrings (Pes Anserinus)

The most common presentation involves the semitendinosus and gracilis tendons snapping over the medial tibial condyle 1, 2. These patients present with:

• Pain and audible/palpable snapping on the posteromedial aspect of the knee
• Snapping occurs when tendons pass over the medial tibial condyle during knee flexion-extension
• Palpable divot or defect may represent the tendon displacement
• Can involve one or both tendons (semitendinosus more frequently involved) 2

Snapping Lateral Biceps Femoris

The biceps femoris tendon can snap laterally, presenting with 1, 3:

• Pain and popping on the direct lateral aspect of the knee
• Snapping more prominent with varus stress during passive flexion-extension
• Easily palpated midway between lateral epicondyle and lateral joint line 3

Snapping Popliteus Tendon

Though less common, the popliteus tendon can snap over the lateral femoral condyle 4, 3, 5:

• Lateral knee pain with snapping sensation
• Positive Cabot sign (consistent clinical finding) 4
• Snapping occurs as tendon moves over the incisura poplitea extensoria 5
• Can be confused with IT band syndrome 5

Baker's Cyst Considerations

While not a tendon, popliteal cysts (Baker's cysts) are relevant in the differential 6:

• Fluid accumulation in bursa of gastrocnemius or semimembranosus muscles
• Can extend far into thigh and calf muscles 6
• Rupture can create palpable defect and mimic deep vein thrombosis 6
• Located between medial head of gastrocnemius and semimembranosus tendon 6

Diagnostic Approach

Clinical examination is paramount:

1. Location specificity: Medial vs. lateral vs. posterior midline

2. Provocative maneuvers:

   • Varus stress during flexion-extension for lateral pathology 3
   • Passive stretch tests for specific tendons
   • Palpation during active movement to reproduce snapping

3. Imaging:

   • Ultrasound can identify tendon pathology, Baker's cysts, and ruptures 6, 7
   • MRI is gold standard but ultrasound is cost-effective alternative 7
   • Arthroscopy remains criterion standard for popliteus pathology 4, 8

Treatment Algorithm

Conservative Management (First-line for all):

• Rest and activity modification
• Physical therapy with eccentric exercises
• NSAIDs for pain control
• Immobilization in acute phase if needed

Surgical Intervention (if conservative fails after 3-6 months):

For medial snapping hamstrings 1, 2:

• Semitendinosus and gracilis tenotomy/release
• Alternative: tendon harvest
• Outcomes: Improvement in Lysholm scores, median satisfaction 7/10 1
• 4/6 patients returned to full activities 1

For lateral snapping biceps femoris 1:

• Isolated biceps femoris repair
• Outcomes: Improvement across all WOMAC domains and Lysholm scores 1
• 5/7 patients returned to full activities 1

For snapping popliteus tendon 4, 3:

• Tendon release or tenodesis to fibular collateral ligament
• Both procedures curative without complications 3
• Arthroscopic securing of tendon to sulcus on lateral femoral condyle 4

Critical Pitfalls to Avoid

1. Don't confuse with more common pathology: Snapping tendons are easily mistaken for meniscal tears, IT band syndrome, or lateral ankle sprains 3, 5

2. Don't perform unnecessary arthroscopy: Accurate clinical diagnosis prevents diagnostic arthroscopy for what may be an extra-articular problem 3

3. Don't ignore the "pop": An audible/palpable pop with a divot strongly suggests tendon pathology or rupture requiring specific evaluation

4. Consider Baker's cyst rupture: If there's a palpable divot with calf extension, rule out ruptured popliteal cyst which can mimic DVT 6

5. Age matters: These snapping syndromes typically occur in patients under 40 without arthritis 3