Discussion:
The anatomy of the biceps femoris tendon is complex and crucial to the biomechanical function of the knee. The muscle, composed of the short and long heads, is involved with hip extension, lateral rotation of the leg, and knee flexion. In addition, the biceps femoris plays an important role as a dynamic stabilizer of the knee and injury has been associated with rotatory instability of the knee.25 A cadaveric study of 56 knees by Salter et al. 2005 found that the biceps femoris tendon is composed of medial and lateral slips and was found to attach to the lateral condyle of the femur, popliteus, and the arcuate popliteal ligament.26
The long head of the biceps femoris originates at the ischial tuberosity and has two tendinous insertions. The first is a direct arm that attaches to the posterolateral fibular head and the second is an anterior arm that attaches to the lateral aspect of the fibular head or the lateral tibial plateau.16, 26 In our case, an anomalous attachment of the biceps femoris to the anterolateral tibia was repositioned to the direct arm insertion to resolve painful snapping of the tendon over the fibular head.
Due to the unremarkable findings on imaging, the diagnosis of a snapping knee due to an accessory tendon is difficult. There is some evidence to suggest that use of dynamic ultrasound may aid in making the diagnosis of a snapping biceps femoris tendon.27 Various surgical approaches have been used to treat snapping of the biceps femoris tendon. One approach is resection of the fibular head.19,20 McNulty et al. successfully resolved symptoms by removing the prominent ridge on the posterior aspect of the fibular head, which caused snapping.19 Fung et al. reported a 17-year-old soccer player with bilateral exostoses at the fibular head treated surgically with exostosis excision, biceps tendon debridement, and fibular prominence smoothening with success.20
In other case reports, the anomalous tendon insertions may be resected.5,13,16 Fritsch et al., reported an enlarged anterior arm of the biceps femoris tendon which elicited snapping. The thickened anterior arm was then detached and shuttled through a fibular tunnel, which resolved the snapping.5 Further, Reid et al. reported painful snapping in a 15 year-old athlete, which was resolved through resection of the accessory biceps femoris attachment and reinsertion into the fibular head with suture anchors and a Krackow suture.16 In Ernat et al., the anterolateral tibial and thickened fibular accessory bands were released without reattachment, which resolved snapping at the lateral knee.13
In Date et al. 2011, an anomalous insertion of the biceps femoris at the anterolateral proximal tibia as well as the anterior arm at the lateral edge of the fibular head were sutured to the direct arm on the posterolateral fibular head using three stitches10. Similar to Date’s case, the accessory band of our patient’s biceps femoris tendon was sutured against the direct arm and periosteum with only stitches without the use of suture anchors. In addition, given the crucial role of the biceps femoris to knee function, we felt that re-attachment of the accessory biceps femoris tendon insertion was more appropriate than a tenotomy alone.
Our patient exhausted all conservative treatment options including anti-inflammatory medications and >2 months of physical therapy, which ultimately exacerbated his symptoms. Past cases of snapping biceps femoris tendons at the lateral knee have been treated uniquely depending on their pathophysiological root. In our case, an accessory anterolateral tibial insertion of the biceps femoris tendon was snapping over the fibular head. Symptoms were successfully resolved by the tenodesis of the accessory band to the direct arm insertion at the posterolateral edge of the fibular head. The patient was able to return to an active lifestyle at 2 months follow-up without recurrence of symptoms.