Popliteus tendonitis is an uncommon pathology that which often occurs in athletes and people with a history of other knee ligament injuries. The pathology involves popliteus muscle which is present on the posterolateral aspect of the knee region.
Popliteus muscle is a key stabilizer of the knee, and plays an important role in maintaining proper mechanics at the knee during walking, running, and climbing stairs.
Relevant Anatomy
Popliteus muscle is unique in that muscle belly is distal and the insertion is proximal.
Popliteus muscle originates from lateral femoral condyle [strongest origin], just anterior and inferior to the lateral collateral ligament origin, from fibula and from the posterior horn of the lateral meniscus.
The muscle inserts on the posterior surface of the tibia above soleal or popliteal line occupying about 10 to 12 cms of the tibia.
The popliteus tendon runs deep to lateral collateral ligament and passes through a hiatus in the coronary ligament to attach to the femur.
It is supplied by Tibial nerve (L4, L5, S1). Blood supply of popliteus muscle is from the medial inferior genicular branch of the popliteal artery and muscular branch of the posterior tibial artery.
Popliteus is an internal rotator of the knee. It assists in initiating knee flexion and early rotational unlocking from the tibia. Unlocking is accomplished contour of articulation & retraction of the posterior aspect of the lateral meniscus.
It rotates the tibia medially on the femur or femur laterally on the tibia depending on which one is fixed. It also works to withdraw the meniscus during flexion in some persons and provides rotatory stability to the femur on the tibia
In addition, popliteus also acts as secondary restraint in preventing posterior tibial translation on the femur.
It prevents posterior translation of the tibia on the femur.
Apart from these, popliteus prevents excessive external rotation of the tibia.
Presentation of Popliteus Tendonitis
Pain is of insidious onset and present along with a posterolateral portion of the knee. The occurrence of the pain is mainly during weight bearing when the knee is between 15-30 degree of flexion [during early swing phase].
History might further reveal a recent activity like downhill running, running on banked surface or backpacking downhill.
The pain is aggravated by running and relieved by rest.
There is tenderness at tendinous insertion at lateral femoral condyle. For palpating the popliteus the lower limb is kept in “fig of 4”.
Findings may absent during rest period and having patient run downhill prior to examination may be helpful.
Joint effusion absent unless concomitant problem.
Lab Studies
Lab studies are generally not required in popliteus tendonitis.
Imaging
Imaging is routinely not required.
Xrays are mostly normal but may show radiodensities in chronic cases.
MRI may be done to rule out intraarticular pathology or tendon avulsion.
Differential Diagnoses
- Lateral meniscal pathology e.g cyst
- Osteochondritis dissecans
- Iliotibial band syndrome
- Lateral collateral ligament injury
- Degenerative joint disease
- Proximal tibiofibular instability.
Treatment of Popliteus Tendonitis
During acute symptoms rest, activity restriction, ice application, compression and elevation of the part should be done.
NSAIDs may be used for relieving pain and decreasing inflammation.
The patients with chronic popliteus tendonitis need activity restriction for a prolonged period. Steroid injections help to alleviate the symptoms.
The acute period is followed by rehabilitation which consists of flexibility exercises and strengthening exercises.
Retraining the functional movement pattern should be undertaken before return to play is allowed. When the patient returns to play, downhill running should be avoided.
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