Symptoms of Posterior Knee Semimembranosus Bursitis
Semimembranosus bursitis presents with posteromedial knee pain that is typically located more superior and posterior than pes anserinus bursitis, often mimicking internal derangement of the knee. 1, 2
Primary Clinical Presentation
- Posteromedial knee pain is the hallmark symptom, with pain localized to the area around the central tendon of the semimembranosus muscle 1
- Pain location is characteristically superior and posterior to the typical location of pes anserinus bursitis, which helps differentiate these two conditions 2
- Tenderness to palpation over the posteromedial aspect of the knee, specifically around the semimembranosus tendon insertion 3, 4
Key Diagnostic Features
The semimembranosus bursa has a distinctive anatomical location and morphology around the central tendon of the semimembranosus muscle, which creates a characteristic clinical presentation 1. This bursa is also known as the semimembranosus-tibial collateral ligament (SMTCL) bursa due to its relationship with these structures 2.
Clinical Mimicry and Differential Considerations
- Can clinically mimic internal derangement of the knee, leading to potential misdiagnosis and unnecessary arthroscopy if imaging is not performed 2
- Symptoms may be confused with other causes of posterior knee pain including Baker cysts, hamstring tendinitis, meniscal pathology, or bursitis of other knee bursae 5
- The pain pattern differs from pes anserinus bursitis, which typically causes pain more inferior and anterior on the medial knee 2
Imaging Characteristics That Correlate With Symptoms
- On MRI, the bursa appears as fluid draped over the semimembranosus tendon in the shape of an inverted U, which corresponds to the anatomical distribution of pain 2
- The typical location and morphology around the central tendon of the semimembranosus muscle can be demonstrated on imaging and correlates with the clinical pain pattern 1
Common Clinical Pitfalls
- Do not confuse this with pes anserinus bursitis, as the pain location is distinctly more superior and posterior 2
- Avoid unnecessary arthroscopy by obtaining appropriate imaging when posteromedial knee pain is present, as this condition can mimic internal derangement 2
- The condition may be under-recognized in clinical practice, as many knee bursae remain underdiagnosed 4