5. Recent advances in sports medicine

In the past, hip joint abnormality was attributed solely to osteoarthritis, but magnetic resonance imaging (MRI) and hip arthroscopy have shown that labral injuries, chondral injuries, rim lesions, synovitis and tears of the ligament teres are common causes of hip, groin and low-back pain. Tears of the acetabular labrum (Box 1) occur as a result of trauma, and more commonly in patients with dysplasia, pelvic instability and degeneration.1 Loading of the hip in hyperextension and external rotation is the mechanism most commonly associated with tearing of the anterior acetabular labrum. Dance, golf, hockey and soccer are associated with a higher incidence of hip injuries.2

The history of a patient with a labral tear ranges from a traumatic event to insidious onset. In more than half of injuries, the patient cannot recall a specific incident.2 Falls and twisting injuries are commonly reported, but other mechanisms include running, direct blows and high-energy trauma sustained from motor vehicle accidents or falls from heights.2 The lumbar spine and groin are the most common sites of pain in patients aged 16–56 years with hip disorder. Commonly, the presentation is subtle, characterised by dull, activity-induced or positional pain that typically fails to improve with time.1 The patient may complain of a catching pain or clicking sensation. Examination findings include a limp, an audible or palpable click during passive flexion-extension, and pain on passive flexion and internal rotation of the hip.

X-ray, arthrography and conventional MRI have all been found to be inadequate in diagnosis.3-5 In the last decade, gadolinium-enhanced magnetic resonance arthrography has been widely used to detect labral abnormalities, although more recent studies 6,7 have suggested that the sensitivity of this procedure may be somewhat less than first reported.3,8 More recently, fast spin-echo proton-density weighted MRI sequences taken in the plane of the hip joint have been shown to be more accurate.9

Intra-articular injection of local anaesthetic combined with examination of the hip before and after injection can be useful in determining the hip as the source of pain.6

Hip arthroscopy is both a diagnostic (gold standard) and therapeutic tool, although it is technically more difficult than arthroscopy of other joints. Distraction of the hip of about 10–15 mm is required to access the hip joint, and most complications, such as neuropraxias, are caused by traction.

In a number of case series, arthroscopy has been shown to be of benefit in recent traumatic labral injury,10-12 but gives disappointing results in chronic hip pain, which is probably associated with degenerative change, and chondral lesions of the acetabulum.13

Overuse knee injuries are the most common musculoskeletal conditions presenting to general and sports medical practices.14-16 Overuse knee pain is usually anterior, inferior or retropatellar, and the most common condition responsible for this pain is patellofemoral pain (PFP).

In PFP, the pain may be localised, but is most likely to be generalised around the patella, and non-specific. It may be precipitated by an increase in the frequency or intensity of repetitive loaded activities (eg, running, walking up and down hills or stairs, squatting). Tenderness is usually localised to the retropatellar area and pain reproduced on step-up, step-down or squat.

Researchers have identified that individuals with PFP have a delayed onset in the activity of the vastus medialis obliquus (VMO) muscle, relative to the lateral quadriceps muscle (vastus lateralis).17,18

Patellofemoral pain is not a self-limiting condition, and physiotherapy generally includes several components: retraining the VMO component, stretching, mobilisation, massage, general conditioning, taping/bracing, foot orthoses, balance training, and hip muscle training. This approach, with its emphasis on training the VMO in a weightbearing position in conjunction with taping of the patella (Box 2), and first described by Australian physiotherapist Jenny McConnell,19 has gained widespread acceptance in Australia and increasingly internationally.

Five systematic reviews of randomised controlled trials, three of which were methodologically sound, have found this multimodal physiotherapy program to be of benefit in relieving anterior knee pain.20-24 In another randomised controlled trial, a multimodal intervention resulted in an earlier onset of VMO (relative to the vastus lateralis) and improved knee flexion during stair ambulation.25-27

Patients with PFP often exhibit reduced core stability (strength and control of the lumbo–pelvic–hip region), which may increase the load on the patellofemoral joint through increased femoral internal rotation and knee valgus. This is often assessed in the clinic using the “step-down or single-leg squat test” (Box 3). The limited research in this area suggests that hip muscle strength is reduced in PFP,28 and most multimodal interventions include a component of hip strengthening and control exercises.

The causes of ACL injury have been extensively studied. In AFL football, ground hardness, grass type (couch) and boot studs have been shown to be associated with ACL injury. Efforts to rectify this include watering grounds, avoiding couch grass and having less foot fixation.29 It is too early to assess their effectiveness.

Women are about three times more likely than men to have ACL injury, possibly because of factors including the effect of differences in hormone levels on ligament strength and stiffness, neuromuscular control, lower limb biomechanics, ligament strength and fatigue.30,31 Differences in neuromuscular control, especially in reduced activation of hamstring muscles32,33 and landing from a jump with less hip and knee flexion than men,32 have been shown to be important factors in the differences between the sexes.

Given the apparent importance of neuromuscular factors in the aetiology of ACL injuries, particularly in women, programs to improve neuromuscular control have been implemented. They aim to improve awareness and knee control during standing, cutting, jumping and landing.34 They have focused on proprioceptive balance-board exercises,35 plyometric training,36 avoidance of high risk behaviour and positioning,37 landing techniques38 or a combination of these.34,38,39 A number of these studies have shown a reduction in ACL injuries of up to 89%.

An ACL-deficient knee is not compatible with moderate-to-high-level sporting activity, especially in sports that involve sudden changes of direction. Arthroscopic-assisted reconstruction of the anterior cruciate ligament after rupture is a common procedure performed by sports orthopaedic surgeons in Australia. Current topics of debate include choice of graft, graft positioning, graft fixation and postoperative rehabilitation. Available ACL grafts include hamstring tendons (semitendinosis and gracilis), patellar tendon, quadriceps tendon, allograft and synthetics. Hamstring and patellar tendon grafts are by far the most common grafts used, and there appears to be no difference in outcomes.40,41 An excellent Australian study comparing the two techniques showed little or no difference in terms of functional outcome, despite greater laxity measurements in patients in the hamstring tendon group. The principal differences between the two graft types in this study, as in others, were increased pain on kneeling and increased extension deficits in patients in the patellar tendon group.42 Allografts appear to be as effective as autografts,43 but problems with availability and cost, as well as theoretical concerns about disease transmission, make this a less popular choice of graft. Synthetic ligaments have been shown to be unsuccessful in the long term.44,45

Microfracture (mesenchymal stem cell stimulation): 1 mm holes are punched into exposed subchondral bone, gaining access to the underlying marrow. Pluripotential stem cells then form a “superclot” and differentiate into fibrous and chondral-like cells. This will result in formation of type 1 collagen with characteristics akin to hyaline cartilage. Advantages include the ability to perform this as an arthroscopic rather than open procedure, rapid rehabilitation and low cost. The main disadvantage is the inferior performance of type I collagen over 2 years.46-48

Autologous chondrocyte implantation (ACI): Autologous chondrocytes are harvested from an area of healthy cartilage and cultured with the use of growth factors to promote chondrocyte growth and differentiation; they are then reimplanted to the chondral defect and held in place beneath a periosteal patch to synthesise and maintain normal chondral matrix. The advantage is the higher degree of hyaline-like (rather than fibrous) cartilage, with possible long-term prevention of osteoarthritis. Disadvantages include high cost, the open procedure involved (with higher morbidity), technically difficult surgery and availability.49 A recent systematic review concluded that the completed clinical trials did not yield any evidence that ACI was superior to other therapeutic alternatives, although the follow-up periods were very short.50

Currently, tissue engineering techniques are being investigated in a number of areas in orthopaedics. Chondral regeneration and osteoarthritis, meniscal regeneration, fracture non-union, prosthetic bioimplantation and ACL reconstruction create the most interest. Most research is directed towards achieving the “holy grail” of a single arthroscopic procedure that reproduces hyaline cartilage with an intact layered architecture.

The mainstream popularity of orthoses was tied to the running boom in the United States in the late 1970s and early 1980s, and the explosion of overuse injuries, attributed to inadequate footwear, or, the new catch phrase, “faulty biomechanics”. However, many of the studies linking foot mechanics directly to musculoskeletal pain are based on conjecture, expert opinion, or case series.51 Although orthotic therapy is reported as successful, such reports are often based on subjective or empirical data,52 and are surprising, given the variability in properties and placement of the orthotic inserts used.

While the mode of action of orthotic therapy is not fully understood, it should not be discounted. By far the most credible theory for orthotic function today is that orthoses provide altered sensorimotor or proprioceptive feedback to the brain, which then produces protective reactions through muscular and neurological responses.53,54 This may explain why the success of orthotic therapy is very operator dependent, so that physicians should refer to podiatrists who are knowledgeable, ethical, and not locked into “standard” orthotic treatment protocols for complex problems.

The sport biomechanist has also become embroiled in the technological advances of sports like cricket, where a bowler’s action may now be placed under the scientific microscope (Box 4). This research has been aided by advances such as the optoreflective motion analysis system (replacing the high speed camera) and computers and models with ever more storage and processing speed. Optoreflective analysis can record movement to within 1°, compared with high speed video systems with error levels of more than 3°.

Motion analysis systems include a wide range of camera and software alternatives that capture and track marker movement, create an anatomically-based image, then determine, for example, the angles, velocities, moments and powers for the movement analysed.

These data may then be linked with data from other exercise scientists, sport physicians and physiotherapists for research or therapeutic purposes. A team approach to research is essential if performance is to be optimised while keeping athletes relatively free of injury.