Popliteus Tendinopathy
The popliteus may be affected by tenosynovitis, acute calcific tendonitis, rupture, and avulsion. Popliteus tendinopathy is rare but often misdiagnosed. Pain may arise from the muscle belly, its tendon, or the popliteus-arcuate ligament complex. Popliteus injuries are commonly seen in combination with injuries to the lateral meniscus and posterior cruciate ligament. Isolated popliteus pathology is less common. Posterior lateral instability may be present.
Anatomy
- Main article: Popliteus
The popliteus muscle has up to three origins - the lateral femoral condyle (just anterior and inferior to the lateral collateral ligament), the fibula head, and in some people also the posterior horn of the lateral meniscus. It inserts into the posterior surface of the proximal tibia proximal to the soleal line.
The muscle is unusual is that its proximal attachment (origin) is tendinous and the muscle belly lies distally. The function of popliteus is internal rotation of the tibia on the femur if the femur is fixed (sitting down) or external rotation of the femur on the tibia if the tibia is fixed (standing up). Along with popliteus, the popliteo-fibular ligament is also important for preventing external tibial rotation. When the knee is in full extension, the femur slightly medially rotates on the tibia to lock the knee joint in place. It unlocks the knee with medial tibial rotation to allow flexion. It also helps to prevent anterior dislocation of the femur / posterior dislocation of the tibia while crouching.
It is supplied by the tibial nerve (L5 and S1) and popliteal artery.
Risk Factors
- Downhill running or other deceleration activities
- Twisting activities
- Sequelae or knee rotational instability for example in posterior capsule-arcuate ligament strain
Clinical Features
History
Pain is usually felt posterolaterally, typically with exercise. The patient may report some instability and comment that it difficult to bend their knee.
Examination
For palpation position the patient prone with the knee flexed. There is generally localised tenderness over the popliteus tendon. Palpate over the course of the popliteus and its tendon. Also palpate over the hamstring tendons and gastrocnemius origin. Asking the patient to contract their muscles can aid in palpation. There may be limitations in knee flexion and extension range of motion. End range may cause pain.
There are two special tests
- Garrick test: patient supine, hip and knee flexed to 90 degrees, leg internally rotated, patient asked to "hold it there" while the examiner passively externally rotates the tibia.
- Passive external rotation: In the same position as above apply passive external force.
Also perform a standard knee exam including assessment of knee alignment and lower limb biomechanics.
Imaging
Calcific changes may be apparent on plan x-ray. MRI may show tendinopathic changes and tenosynovitis.
Treatment
Physical Therapy
Physical therapy is targeted at eccentric strengthening of the quadriceps to reduce strain on the popliteus. The rehabilitation program should also include strengthening of the tibial rotators and hamstring muscles.
Injections
Anecdotally the condition responds well to corticosteroid injection. A typical dose is 10mg triamcinolone injected into the area of maximal tenderness. Ultrasound can be used for increased accuracy.
References
- Brukner, Peter, and Karim Khan. Brukner & Khan's clinical sports medicine. Sydney New York: McGraw-Hill, 2012.
Literature Review
- Reviews from the last 7 years: review articles, free review articles, systematic reviews, meta-analyses, NCBI Bookshelf
- Articles from all years: PubMed search, Google Scholar search.
- TRIP Database: clinical publications about evidence-based medicine.
- Other Wikis: Radiopaedia, Wikipedia Search, Wikipedia I Feel Lucky, Orthobullets,