Vastus Micromedialis Essay

Vastus Medialis
Gross Morphology
The vastus medialis (VM) is a muscle situated in anteromedial aspect of the thigh. It forms quadriceps femoris muscle by the three distinctive portion, the rectus femoris, vastus lateralis and vastus intermedius (Palastanga and Soames 2012). The Vastus medialis has been termed as being composed of two separate division: the vastus medialis longus proximally, and the vastus medialis oblique distally (Hubbard et al 1997).
The vastus medialis (VM) origin form a line starting at the inferior medial end of the intertrochanteric line, running inferior around the medial aspect of the upper end of the shaft on the spiral line, the linea aspera, located on the posterior surface of the femur, and extends on to the uppor third of the supracondylar line, the medial intrermuscular septum. The vastus medialis fibres orientated differently upper fibres pass primarly downwards and lower fibres tend to pass almost horizontally and laterally (Palastanga and Soames 2012). It goes from back to front covering femur and it shows widespread development of fivers that sub divide into two “heads” the superior head forms the longitudinal portion of the muscle called VM longus and the inferior head originate from
the adductor magnus and adductor longus tendon and form the oblique part of the muscle called VM obliquus (Peeler et al 2005). The VM obliquus inserts more on to medial border of the patella which causes medially pull to the patella (Tenan et al 2013). The vastus medialis muscle attaches to the tendon of rectus femoris then inserts on to medial border of the patella, front of the medial condyle of the tibia, and to the tibial tuberosity (Palastanga and Soames 2012).
The innervation supply to vastus medialis (VM) is musculature branches of femoral nerve (L2, L3, L4). The pathway of the femoral nerve from lumbar root to the muscle, drive along with femoral vein, artery and saphenous nerve and enter to the adductor canal also called Hunter’s Canal. It divide into branches that supply vastus medialis and the knee joint after passing to adductor canal (Ozer et al 2004). The artery supply for the vastus medialis (VM) is femoral artery, profunda femoris artery, and superior medial genicular branch or popliteal artery (Palastanga and Soames 2012)
As noted by Peeler et al (2005), the vastus medialis consist of two “head”, the oblique and long head both have different muscle fiber orientation, but his study through dissection of 32 limbs from 24 intact cadaver with normal patellar alignment has shown that there was only few anatomical evidence that supports that the oblique and long head of the vastus medialis have structural architecture designed to support specifically different function. Another study done by Willis et al (2005), indicated that the vastus medialis oblique activation could be appropriate and beneficial treatment of patelofemoral knee pain and postoperative patellofemoral rehabilitation.
According to Tenan et al (2013), there is higher incidence of patellofemaoral pain in women due to motor units of the VM and VMO are differentially recruited, and initial motor unit firing rate significant lower in the VMO than that in the VM in women but not in men. Motor units activation differs between the VM and the VMO and across the menstrual cycle. This could influence higher incidence of patellar pathologies in women (Tenan et al 2013).
Function and Clinical relevance
The vastus medialis function is extension of the lower limb at the knee joint, it is the key muscle to the knee joint for the final 15 degrees of the knee extension (Nozic et al 1997).
As noted by Sheehan et at (2012), previous cadaver and EMG studies shown VM plays significant role in medial stabilizing the patella. The two head of the VM provided different stability of the patella. The VM longus contributes to knee extension, and VM oblique provide medial stabilization of patella during knee extension (Hubbard et al 1997). VMO provide greater stability of the patella compare to VML in knee extension in the particular individual, due to the angular orientation of the VMO muscle fibre (Nozic et al
1997).
The patellofemoral joint is frequently affected due to several factor such as instability, incongruence, subluxaton, or excessive presser around the knee, the balance of the quadriceps muscle is important factor in patellofemaoral joint stability. The variations in the attachment of the VL and VM cause for patellar instability (Sakai et al 2000). According to Farahmand et all (1998), the function of the different heads of the quadriceps has important role in the stability of the patella throughout the knee movement. This applies particularly to the magnitude and directions of action of the VM with the interaction of the patella, and their transverse and posterior orientations. The weakening of the vastus medialis oblique causes patellar shift 0 and 15 degree of knee flexion (Sakai et al 2000).
Patellofemoral pain mostly affects young adults and physically active adolescents. The imbalance between vastus medialis and vastus lateralis strength, and altered neuromuscular timing have all been described as patellofemoral pain syndrome. Also, an individual variability in anatomical risk factor has also been described in patient cohort (Balcarek et al 2014). Patellofemoral pain syndrome (PFPS) is mostly caused anterior knee pain due to aberrant motion of the patella in the trochlear groove, this results into physical changes within the patellofemoral joint. The sign and symptom of PFPS are crepitus, anterior knee pain exacerbated during running, squatting, jumping or waking down stairs. Pain may experience during full flexion of the knee, feeling of catching or locking at the knee joint. Stiffness and swelling sensation at the knee joint, and “bucking” feeling in the knee while walking. Despite this, it is common for patients to give an unclear description of the site of their pain (Green, 2003).