Weight bearing

In standing, each hip takes roughly 0.3 times bodyweight, increased to 2.4 times body weight when standing on one leg. Weight-bearing forces of up to 4.5 times bodyweight may be taken on the hip in running (Magee, 2002). In order to take weight most effectively, bony trabeculae line up in the direction of imposed stress. Two major systems exist within the femur (Fig. 8.2). The medial trabecular system travels from the medial cortex of the upper femoral shaft to the superior aspect of the head. This system takes vertically aligned forces created by weight bearing, and is aligned with the superior aspect of the acetabulum, the main weight-bearing region. The lateral trabecular system begins from the lateral cortex of the upper femoral shaft, crosses the medial system, and terminates in the cortical bone on the inferior aspect of the head. The lateral system is aligned to take oblique forces created by contraction of the hip abductors during gait.

Figure 8.2 Bony trabeculae of the upper femur.

After Norkin, C.C. and Levangie, P.K. (1992) Joint Structure and Function, 2nd edn. FA Davis, Philadelphia. With permission of the publisher FA Davis.

In addition to the medial and lateral trabecular systems, the upper femur is reinforced by medial and lateral accessory systems which take forces created about the trochanters. A zone of weakness is left within the femoral neck which is susceptible to bending forces and is the site of femoral neck fracture (Norkin and Levangie, 1992).

Hip ligaments

The hip joint is strengthened by three capsular ligaments: the iliofemoral ligament and the pubofemoral ligament are on the anterior aspect of the joint, while the ischiofemoral ligament is on the posterior aspect (Fig. 8.3). As the hip is flexed, all three ligaments relax. However, in extension all three ligaments are tight, with the inferior band of the iliofemoral ligament being placed under greatest tension as it runs almost vertically. It is this ligamentous band which limits posterior tilt of the pelvis (Palastanga, Field and Soames, 1994).

Figure 8.3 Capsular ligaments of the hip joint.

After Palastanga, Field and Soames (1994), with permission.

During adduction, it is the turn of the superior band of the iliofemoral ligament to become tighter while the pubofemoral ligament and ischiofemoral ligament relax. In abduction the opposite occurs. In lateral rotation both the iliofemoral ligament and pubofemoral ligament are taut, while in medial rotation the ischiofemoral ligament tightens.

Muscle imbalance around the hip

The concept of muscle imbalance was covered in Chapter 5. In the hip region, the Thomas test and the Ober manoeuvre are used to assess for muscle tightness of the hip flexors (rectus femoris and iliopsoas) and hip abductors (tensor fascia lata and iliotibial band – TFL/ITB). Inner range holding ability of the gluteus medius is assessed with side-lying hip abduction and of the gluteus maximus with the prone-lying hip extension movement described below. Segmental control tests include standing hip flexion, standing hip abduction and the hip hinge (Table 8.1). All tests are described in Chapter 5.

Table 8.1 Muscle imbalance around the hip

Quadriceps

On the whole, strains occur mostly in two-joint muscles, due to the more complex coordination involved in controlling movement of two body segments simultaneously. Direct trauma, however, can be imposed on any muscle. In the hip region, this means that the rectus femoris, hamstrings and gracilis muscles tend to suffer strain. The more anterior position of the quadriceps, however, exposes these muscles to risk during contact sports, and to blunt trauma through collision with sports apparatus. A quadriceps contusion is often referred to colloquially as a ‘dead leg’ or ‘charley horse’.

Initially, there is local swelling over the front of the thigh, with some superficial bruising appearing later, often tracking down to the knee. The main danger with this injury is the development of myositis ossificans traumatica (MOT). Thigh contusions may be rated as grade 1 (mild), in which knee flexion beyond 90° is possible, grade 2 (moderate), in which motion is restricted to 45–90°, or grade 3 (severe), in which swelling and pain limit movement to less than 45°. This grading system can be an accurate predictor of the likelihood of MOT development. Jackson and Feagin (1973) assessed quadriceps contusions in 65 subjects, and found that none of the subjects with grade 1 injuries had developed MOT. However, 13 out of 18 subjects who had been graded 2 or 3 later went on to develop the condition, so the amount of movement present in the initial stages is an important indicator of the severity of the lesion, and the prognosis.

It is important to limit movement in grade 1 and 2 injuries and to discourage the use of massage, vigorous stretching or exercise and ultrasound, as these are contraindicated in the early post-injury stage. The RICE protocol is used to limit the tissue damage. Ice is applied with compression with the knee and hip flexed as far as is comfortable. Internal compression is therefore applied by fascial tightening (Reid, 1992), while external compression comes from the elastic bandage.

The athlete resuming contact sports should wear padding over the damaged area, to reduce the risk of secondary injury. It is important that full broadening of the muscle belly be obtained during rehabilitation. This will involve resisted quadriceps exercises, beginning with low intensity and building eventually to maximum voluntary contractions (MVC). This is equally important to endurance athletes as to power athletes. Often, distance runners, for example, do not use weight training, focusing instead on stretching. For this injury, however, longitudinal movement of the muscle is less important than lateral movement (broadening). This is because the rectus femoris, being a two-joint muscle, may limit movement, but the vasti, being single-joint muscles, do not. As the vasti form the bulk of the injured tissue, stretching, although important with this injury, is secondary to strength training.

In cases of MOT, calcification is slow, with fibroblasts beginning to differentiate into osteoblasts about 1 week after injury. Radiographic evidence of bone formation is usually visible after 3 weeks (Fig. 8.4). By 6–7 weeks after injury, the calcified mass generally stops growing. Total reabsorption may occur with minor lesions, but more major conditions may continue to show remnants of the mass. The mass rarely interferes with muscle contraction, so excision is not normally required (Estwanik and McAlister, 1990).

Figure 8.4 X-ray showing myositis ossificans traumatica (MOT).

From Magee (2002) with permission.

Rectus femoris

The rectus femoris is frequently injured by a mistimed kicking action. On examination, pain is usually apparent to resisted knee extension and hip flexion. Passive stretch into knee flexion coupled with hip extension and adduction is also painful. Injury is usually to either the upper insertion or the mid-belly. Upper insertion injuries are palpated with the patient half-lying to relax the muscle. The area of injury is usually the musculotendinous junction approximately four finger widths below the anterior superior iliac spine.

Tenderness to the reflected head attaching to the anterior inferior iliac spine in a youth should raise the question of avulsion injury and may require x-ray confirmation.

Mid-belly tears are less common and are usually sited within the middle third of the thigh. Here, the muscle is subcutaneous and any swelling is immediately apparent. The athlete should flex the hip and knee to 45° against resistance, and as the muscle stands out any abnormality will become apparent.

The rectus femoris can be worked concentrically by flexing the hip against a resistance supplied by a weight bag attached to the knee. Two-joint action of the muscle can be worked with the athlete in supine with the injured leg over the couch side, flexed at both the knee and hip. Manual resistance is applied to the foot of the athlete as he or she extends the knee and flexes the hip simultaneously (Fig. 8.5A).

Figure 8.5 (A) Rectus femoris strengthening combining hip flexion and knee extension against elastic band resistance. (B) Rectus stretch. (i) Correct with pelvis fixed. (ii) Incorrect, anterior pelvic tilt throws stress on lumbar spine. (C) Alternate leg lunge. Front leg stresses quadriceps and gluteals, rear leg stresses hip flexors and knee extensors.

Stretching must involve both knee flexion and hip extension and can be carried out in a side-lying position by the athlete, or by the therapist. When performing a rectus femoris stretch in standing (Fig. 8.5B), the abdominal muscles must be tightened to stabilize the pelvis before the hip stretch is applied. Failure to do so will increase the apparent range of motion by anterior tilt of the pelvis with stress thrown on the lumbar spine. Lunging actions are also useful, for both general flexibility and eccentric control (Fig. 8.5C).

Results are generally very good, even with complete tears (Fig. 8.6), where full function may be regained even though a marked muscle deformity is present.

Figure 8.6 Rectus femoris tear.

From Reid (1992) with permission.

Sartorius

Injury to the sartorius is usually an avulsion from the anterior superior iliac spine. There is usually immediate pain, often radiating into the anterior thigh. Swelling and bruising is seen over the iliac crest, often tracking down the thigh. Flexion/adduction of the hip with flexion of the knee causes pain. Displacement of the bone fragment may be from a few mm to 3 cm, but although surgical reattachment of the bone fragment has been described (Veselko and Smrkolj, 1994), conservative treatment normally suffices. The athlete should be non-weight bearing initially, followed by partial weight bearing ambulation for 3–6 weeks, depending on the intensity of pain. Full strength and flexibility must be regained before competitive sport is resumed.

The hamstrings

The hamstrings may be injured either at their attachment to the ischial tuberosity or within their mid-bellies and, less commonly, at the knee (see below). The hamstring pull is the classic sprinting injury, with the athlete spectacularly pulling up in mid-flight with obvious pain.

Pain is apparent on straight leg raising and resisted knee flexion. Resisted flexion and tibial rotation will determine whether the biceps femoris or semimembranosus and semitendinosus is affected.

To palpation, the structure of the muscles differentiates them. The semitendinosus and long head of biceps have a combined attachment on the lower medial facet of the ischial tuberosity, the two muscles travelling together for a short distance until they form fusiform muscle bellies. The semitendinosus almost instantly forms into a long slender tendon, and travels around the medial condyle of the tibia to attach to the medial surface of the tibia below gracilis. The biceps has two proximal attachments; the long head, as described, and the short head from the lower linea aspera. The muscle swings downwards and laterally across the posterior aspect of the thigh and around the lateral ligament to insert into the head of the fibula. The biceps has a dual innervation, and asynchronous stimulation of the two heads has been described as a factor in injury (Burkett, 1975). The semimembranosus comes from the lateral facet of the ischial tuberosity and travels down and medially, becoming flattened and broader as it does so. The semimembranosus is deep to both the semitendinosus and biceps, and divides into five components when it reaches the knee. The principal insertion is to the posterior aspect of the medial tibial tubercle.

Exercise therapy following hamstring injury

Strength

Exercise therapy aims to progressively increase the function of all the fitness components relevant to hamstring function. Strength restoration begins with isometric contractions within the pain-free range to facilitate muscle broadening and reduce adhesion formation. Concentric strength is later introduced against limb resistance initially, followed by therapist resistance and later light-weight resistance. Knee flexion may be used in both lying and standing. Hip extension (from outer to inner range) is used in prone lying and also standing. The two may be worked in PNF patterns using hip extension, abduction and external rotation combined with knee extension, and the reverse using hip flexion, adduction and internal rotation combined with knee flexion. Both patterns are used initially against controlled therapist resistance but may be later usefully modified against elastic band or pulley resistance.

Where isokinetics are available, a variation of speeds is important. Slow speeds of 60° and 120°/s may be used to begin with, progressing to 240° and 300°/s as pain allows. Hamstring isolation exercises, such as leg curls in lying and standing (Fig. 8.7), have their place in initial rehabilitation to ensure maximal muscle broadening, but have distinct limitations which must be recognized. First, these exercises work only the knee flexion function of the hamstrings, with little activity over the hip. Second, the action is open chain only, when the predominant function of the hamstrings occurs in closed chain format. Third, the exercises are often performed with the emphasis placed on inner-range contraction, which may tend to shorten the muscle. The hamstrings are unlikely to be posturally lengthened so that they require shortening. It is more likely that the muscles will already lack flexibility, so full range resisted work is preferable.

Figure 8.7 Hamstring isolation exercises. (A) Standing leg curl. (B) Lying leg curl. These are non-functional movements which must be used with caution.

Keypoint

Weight training machines often work the hamstrings only in open chain format. This type of action often shortens the hamstrings and works them at the knee only. Closed chain actions involving simultaneous knee and hip movement are more functional.

Eccentric training

Eccentric training of the hamstrings is an important component of rehabilitation. At the end of the swing phase of gait, the hamstrings decelerate the limb by eccentric action, and so preparing the athlete for this action is essential. Eccentric training has been shown to favourably affect the length−tension curve of the hamstrings measured on an isokinetic dynamometer (Clark et al., 2005). Subjects showed a 19.4% change in the position of peak force creation towards the extended knee which may protect against eccentric overload at the end of the swing phase. Eccentric hamstring training of this type has been shown to reduce the incidence of injury in elite soccer (Arnason et al., 2008), and to successfully rehabilitate Australian rules football players (Brughelli, Nosaka and Cronin, 2009). Eccentric exercises include box drops, negative lunges and eccentric leg extension from high kneeling (Nordic hamstring exercise) (Fig. 8.8).

Figure 8.8 Eccentric hamstring exercise.

Closed chain actions

Closed chain exercises may be performed by modifying many common exercises. Leg rowing (Fig. 8.9A) is a useful exercise. The athlete sits on a towel (on a wooden floor) or plastic tray (on a carpeted floor) with the feet fixed. The action is to pull the body forwards by hamstring action, mimicking a rowing position. Sitting astride a gym bench or ‘form’ (Fig. 8.9B), the athlete digs the heels into the ground and again pulls the body forwards using leg strength alone. Both of these actions may be performed unilaterally or bilaterally. The slide trainer may also be used for sagittal leg pumping actions with the knees straight or bent (Fig. 8.9C). The sitting leg press weight training apparatus may be used for the sprint kick exercise (Fig. 8.9D). Instead of sitting on the bench, the athlete turns around and places the shoulder against the chair back, and the ball of the foot on the machine pedal. The action is to press the machine pedal with a combined hip and knee extension action.

Figure 8.9 Hamstring exercises in closed kinetic chain. (A) Athlete sits on a towel on a wooden floor with feet fixed. Pull body forwards by flexing the knees and hips. (B) Sitting astride a gym bench, grip the feet against the floor and pull the body forwards. (C) Using a commercial slide trainer, straight leg hip flexion and extension is performed. (D) Kneeling on a seated leg press machine, hip and knee extension is performed.

Speed, power and flexibility

Speed and power are worked using plyometric activity. Stepping, jumping, lunging and hopping actions are all useful and are progressed for range and speed against body weight resistance and for power against weight resistance. For this later aspect, a weighted jacket is easier (and safer) than holding weights.

Flexibility exercises for the hamstrings must take account of pelvic action and the action of the two-joint muscle. In addition, relative flexibility may dictate that the majority of the stretching force is imposed on the lumbar spine in toe-touching type movements (Fig. 8.10A).

Figure 8.10 Hamstring flexibility exercises. (A) Tight hamstrings limit anterior pelvic tilt, throwing stress onto the less flexible thoracolumbar junction. (B) Active knee extension. (C) Tripod stretch.

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