What is the role of the knee pes anserinus in knee stability and function?

Role of the Pes Anserinus in Knee Stability and Function

The pes anserinus plays a critical role in providing medial knee stability, controlling rotational movements, and supporting overall knee function through its unique anatomical position and biomechanical properties.

Anatomical Structure

• The pes anserinus ("goose foot") is a common tendon formed by the conjoined insertions of three muscles: sartorius, gracilis, and semitendinosus, which attach at the anteromedial aspect of the proximal tibia 1, 2
• This structure inserts below the medial tibial plateau and plays a significant role in stabilizing the medial side of the knee joint 1
• The insertion site serves as an important anatomical landmark and functional unit for knee biomechanics 2

Primary Functions in Knee Stability

• The pes anserinus serves as a primary dynamic stabilizer against valgus stress and external rotation forces applied to the knee 3
• It provides crucial medial knee stability, particularly during the stance phase of gait in patients with knee instability 3
• Electromyographic studies show that the pes anserinus muscles demonstrate increased activity during stance phase in patients with knee instability, suggesting their role in controlling instability 3
• The structure helps prevent excessive anterior translation of the tibia, working synergistically with the anterior cruciate ligament 3

Role in Knee Biomechanics

• The pes anserinus muscles contribute to controlling rotational movements of the knee, particularly internal rotation of the tibia 3
• These muscles work harder in patients with knee instability compared to individuals with normal knees, as demonstrated by quantitative electromyography 3
• The pes anserinus helps maintain proper knee alignment during weight-bearing activities, particularly in individuals with malalignment issues 4
• It assists in distributing load across the knee joint, which is particularly important since approximately 70-80% of joint load passes through the medial compartment during mid-stance phase of gait 4

Clinical Significance

• Dysfunction or injury to the pes anserinus can lead to medial knee instability and altered gait mechanics 3
• Pes anserinus pain syndrome is common in overweight and obese women over 50 years of age and often accompanies knee osteoarthritis 5, 6
• The severity of pain in the pes anserinus area correlates with the intensity of degenerative changes in the knee joint 5
• Avulsion injuries of the pes anserinus tendon are rare but can occur with recurrent lateral patellar dislocations 1

Therapeutic Considerations

• For patients with knee osteoarthritis experiencing pes anserinus pain, treatments like platelet-rich plasma injections have shown effectiveness in providing pain relief 5
• Strengthening exercises targeting the pes anserinus muscles are important for knee rehabilitation programs, particularly for patients with medial knee instability 4
• In cases of severe medial knee instability, the pes anserinus transfer (Slocum and Larson procedure) has been shown to be kinetically sound for controlling anteromedial rotatory instability 3
• Bracing may help support the function of the pes anserinus in patients with medial knee instability, with tibiofemoral knee braces strongly recommended for patients with knee OA experiencing joint instability 4

Relationship to Knee Osteoarthritis

• Weakness in the muscles that form the pes anserinus can contribute to the development and progression of knee osteoarthritis 4
• Quadriceps weakness, which often accompanies pes anserinus dysfunction, is associated with decreased joint stability and shock-absorbing capacity, contributing to disability in knee OA 4
• Strengthening exercises designed to improve muscle strength and joint proprioception, including the pes anserinus muscles, can reduce pain and improve mobility in patients with OA 4
• The pes anserinus may be subject to enthesopathy and bursitis in patients with knee OA, contributing to medial knee pain 5, 6