Anatomy of the lateral retinaculum of the knee.
The authors of this paper studied 35 cadaver specimens to determine the anatomy of the 'lateral retinaculum' - the fibrous area extending from the patella to the lateral part of the knee. They determined that there is no discrete structure making up the lateral retinaculum, but that it is composed of ill-defined anatomical elements from several different structures.
They identified three layers making up this region -
1. The most superficial layer
The first layer deep to the skin and subcutaneous tissue is the deep fascia from the muscles of the thigh. The fascia extends over the patella but is easily separated from it. Laterally the fascia becomes thickened to form part of the iliotibial band (ITB), which band is anchored to the femur just under a centimetre higher than the widest part of the patella when the leg is straight. Thus this layer is not adherent to the patella but is anchored to deeper tissues at the side of the patella, acting like a brace.
2. The intermediate layer
The intermediate layer is the most substantial of the three layers and consists of -
- fibres from the aponeurosis of the quadriceps muscle. The quadriceps muscle and tendon lie deep to the deep fascia layer. Where the quadriceps muscle becomes the quadriceps tendon a little way above the patella, a thin aponeurotic sheet leaves the tendon and anchors laterally to the deep fascia layer.
- fibres from the iliotibial band. The bulk of the iliotibial band runs longitudinally down the lateral part of the thigh to attach to Gerdy's tubercle on the side of the tibia, but bands of fibres sweep obliquely from the iliotibial band to converge with those of the quadriceps aponeurosis above and to the side of the patella.
- the transverse retinaculum. This includes deeper dense transverse fibres that anchor the lateral edge of the patella and the tendon of vastus lateralis obliquus (VLO) to the iliotibial band (but not to the femur).
So this layer only attaches to bone indirectly via the bony attachments of the iliotibial band.
3. The deeper layer
Key points from this article
- The lateral retinaculum has complex anatomy which is difficult to delineate because of converging and interdigitating structures.
- The superficial fascia layer acts like a brace and is not attached directly to the patella, but rather to the structures to the side of it.
- The middle layer is a tensioning layer - both the vastus lateralis (via its aponeurosis) and the iliotibial band affect the function of the lateral retinaculum. A tight iliotibial band is likely to play a role in aggravating lateral patellar tracking.
- The deepest capsular layer is the only one attaching the patella directly to the femur.