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.