This is a review of literature surrounding hamstring strain injuries. Hamstring strain injuries are common and are a major cause of time lost from sports, it is most common in sports that involve jumping and sprinting (Woods et al. 2004).
Anatomy
There are three muscles that make up the hamstring muscle group. Semitendinosus originates on the lower medical facet of the ischial tuberosity and inserting at the medial condyle of tibia. (Banks, 2010)
Semimembranosus originates on the lateral facet of ischial tuberosity and inserts on the posteriomedial part of the medial tibial condyle. (Banks, 2010)
Biceps femoris (BF) originates on the ischial tuberosity and inserts on the head of fibula (Banks, 2010).The BF has two heads both with separate nerve supplies (Williams, 1980), because of this dual innervation, this could lead to asynchronous stimulation of the two separate heads, causing mistimed contractions between the muscle group, leading to reduced capability to create effective tension within the muscle to control the imposed loads (Zuluaga,1995). There are anatomical variations in the attachment sites of BF, which may predispose some people to injury more than others (Burkett, 1975), found that an extensive femoral attachment of the short head of BF, with a strength deficit increased the risk of a HSI.
The insertion of the long head of the BF is thought to also have an affect of the hamstrings, a previous knee or ankle injury which has caused a alteration in the movement of the superior tibiofibular joint would alter the biomechanics of the BF (Woods et al 2004). Zuluga et al (1995) found that incomplete knee excursion caused by a menisci injury, may lead to excessive loading on the BF.
Because BF also acts as a lateral rotator when the knee is semi-flexed and extended hip (Williams 1980), this is also a possible cause of a HSI.
The high incidence of injury to the hamstring muscle group is partly because the group function over the hip joint and the knee joint (Orchard 2002; Hawkins 2000; Cibulka 1986). Orchard (2002) and Devlin (2000) state that the hamstrings have a greater proportion of fast twitch fibres, compared to any other muscles within the leg, this means they are capable of the greatest force production.
Mechanism of Injury
HSI are described as acute pain in the posterior thigh with disruption of the hamstring muscle fibres. Ekstrand and Gillquist (1983) stated that the three types of grades were:
Grade I is a mild strain or contusion, which is a tear of a few muscle fibres with minimum swelling and discomfort with minimal or no loss of restriction or function. Grade II as a moderate strain or contusion, with greater damage to the muscle fibres with a clear loss of strength. Grade III as a severe strain or contusion, with a tear that extends across the whole cross section of the muscle, causing a total lack of function.
According to Koulouris et al (2003, 2007) and Verrall (2003), the biceps femoris is the most commonly injured muscle from the hamstring muscle group. Sherry et al (2011) found that HSI occur while running, Garret (1996) and Orchard (2002) expanded on this and found that strains occur during the terminal swing phase of the gait cycle while running. Verrall (2001) confirmed this and analysed the biomechanics of running, and found that hamstring strains occur during the end of the swing phase; this is when the hamstrings are working to decelerate the limb, while also controlling the knee extension. During this the hamstrings must change from eccentric contraction, to decelerate the knee extension in the lat swing to concentric contraction and becoming an active extensor of the hip joint. This rapid changeover from eccentric to concentric is when the hamstrings are most vulnerable to an injury (Verrall 2001).
Pinniger et al (2000) found that fatigue during sprinting caused an earlier activation of the BF and semitendinosus muscles, predisposing the muscle to injury.
Immediate Treatment
Remove the player from play in order to prevent further injury. Then follow the RICE principles, the aim of this is to control haemorrhaging and reduce the inflammation in the area, and also reduce pain (Petersen and Holmich 2005)
Special Tests
The main purpose of the physical examination is to determine the location and severity of the injury (Heiderscheit et al. 2010).
The strength of the muscles are tested using isometric muscle tests, in mid range as this is the safest and strongest point (REFERENCE).
The range of motion is assessed by using the hamstring tightness test to see how much range of movement the patient has before it is too painful or restricted. To do this the patient lies supine, and the examiner performs a straight leg raise test it should reach at least 80 degrees (Banks, 2010), if this is not reached then this is a positive sign of tight hamstrings.
At the end of the physical assessment, palpation can be used to confirm the prognosis, by using palpation a therapist can identify the specific point of pain through provocation, and there may also be a palpable adhesion present (Heiderscheit et al 2010). Heiderscheit (2010) stated that only the location of the point of maximum pain relative to the ischial tuberosity, while in full extension is associated with the recovery period. The more proximal the site of pain is from the ischial tuberosity, the greater period of time needed to return to the pre-injury level.
Rehabilitation
The hamstrings must become functionally strong in the phase of injury before they are able to return back to play. Garrett et al (1984) suggests that rehabilitation and training should be performed at a high intensity and in high speed situations, as this is often when most hamstrings are injured. Jonhagen et al (1994) supported this as the reason for recurrent injury is down to poor eccentric strength of the hamstrings, at high angular velocities.
A study by Sherry and Best (2010) performed rehabilitations with 11 athletes on a programme of static stretching isolated progressive hamstring resistance and icing (STST) and 13 on a programme of progressive agility and trunk stabilisation exercises and icing (PATS). This study found no significant difference between the groups regarding the time taken to return to sport, however there was a significant difference in the rate of re-injury. Six of the eleven subjects from the STST group has a reoccurrence of a HSI within six weeks, and only one of the subjects from the PATS group. Within one year of the rehabilitation, seven of the STST suffered a reoccurrence and only one of the PATS group. However this is only one randomised controlled study within the literature and further research is needed to say which is most beneficial.
The main goal at the end of rehabilitation is to maintain the stretching and strengthening plan in order to reduce the risk of re-injury (Petersen and Holmich 2005).
