Hamstring Strains:
What causes a hamstring strain?
Hamstring strains are often caused by a rapid extensive contraction or a violent stretch of the hamstring muscle group which causes high mechanical stress. This results in varying degrees of rupture within the fibres of the musculotendinous unit. The hamstrings are at higher risk of injury during the second half of swing phase, when the hamstrings are lengthened and generate high levels of tension. At this stage, hamstrings contract eccentrically to decelerate flexion of the hip and extension of the lower leg. Because a peak is reached in the activity of the muscle spindles in the hamstrings, strong contraction of the hamstring and relaxation of the quadriceps is required (Klafs & Arnheim, 1968). Breakdown in the coordination between these opposite muscles can be a cause for the hamstring to tear. Of all of the hamstring muscles, the biceps femoris is the most common culprit in hamstring strains during high speed running (Heiderscheit et al, 2010).
Common signs and symptoms:
When hamstring strains occur, a feeling of tearing +/- popping may be felt and the clinical presentation will depend on the grade/severity of the injury.
• Grade 1 (mild) strains result in only a few fibres being disrupted and muscle power and endurance are thus less likely to be impacted. Pain and stiffness are usually experienced the day following injury. Expected recovery time is 1-3 weeks.
• Grade 2 (medium) strains approximately half the fibres are torn and symptoms include pain, swelling and mild function loss. Gait and walking tolerance are also more likely to be effected. Pain can be reproduced by applying resistance to knee flexion. Expected recovery time is 3-6 weeks.
• Grade 3 (severe) strains range from more than half of the fibres being torn to complete rupture of the hamstring muscle resulting in exacerbated severities of swelling, pain and muscle weakness (Petersen et al, 2005). Recovery time can take between 6 weeks to 6 months.
Risk factors:
Hamstring tears are highly prevalent amongst sporting populations, particularly AFL, soccer and American Football where eccentric hamstring contractions are very common. Other risk factors that make individuals more susceptible to hamstring injuries include older age, previous hamstring injury, limited hamstring flexibility, previous knee injury and excessive anterior pelvic tilt.
Differential diagnosis:
• Muscle cramps
• Referred pain from lumbar spine due to disc prolapse, protrusion or degeneration.
• Compartment syndrome
• DVT
• Proximal hamstring tendinopathy
Treatment:
1) Hamstring strains include pain management and early mobilisation. It is recommended that individuals follow the PEACE and LOVE protocol immediately following injury.
Acute inflammatory phase (in first 3-5 days post injury):
• Protect – unload or restrict movement (especially knee flexion of the affected hamstring). Move only within pain limits.
• Elevate
• Avoid anti-inflammatory modalities – it has been suggested that NSAIDs and ice may hinder important healing effects of the inflammation process
• Compress
• Educate – individuals should be empowered to take an active approach to recovery. Education should include basic information about their condition, how to safely manage load, rehab expectations and recovery timeline.
Rehab commences:
– Stationary bike 3x5min
– Sub-maximal isometric knee-flexion at 90, 60 and 30 degrees. 3×8-15 reps +3second holds.
– Balance board 3x30sec — progress duration as tolerable.
– Pain-free isotonic knee flexion. 3×8-20reps
– Soft tissue massage
– Progressive hip strengthening.
2) Goals of therapy are then focused on regaining pain-free hamstring strength, progressing through full ROM and developing neuromuscular control with a progressive increase in movement and speec in preparation for functional task execution.
• Precautions: Avoid end-range lengthening of hamstring if pain limited.
Rehab modalities:
• Stational bike: Progression of volume, duration and resistance.
• Soft tissue massage.
• Nordic hamstring extension.
• Eccentric knee extension in the non-lengthened state 3×8-15
• Hamstring curls focus of eccentric lengthen with light resistance 3×8-15
• Single leg stance with perturbations.
• Single limb balance windmill touches 3×5 each way.
3) Aim pain-free return to activity and normal concentric and eccentric strength through full ROM and speed.
• 10 metre acceleration and deceleration.
• Eccentric knee extension at end range.
• Single limb balance windmill touches with weight on an unstable surface.
• Sports specific drills that incorporate postural control and progressive speed.
• Jump squats 3×8-15
• Lateral bounding 3×8-15
• Single and double leg deadlifts 3×8-15.
References:
1. Klafs CE, Arnheim DD: Principles of Athletic Training, Ed pp 370-372. St Louis: CV Mosby Co. 1968
2. Heiderscheit BC, Sherry MA, Silder A, Chumanov ES, Thelen DG. Hamstring strain injuries: recommendations for diagnosis, rehabilitation, and injury prevention. journal of orthopaedic & sports physical therapy. 2010 Feb;40(2):67-81.
3. Petersen J, Hölmich P. Preventie van hamstringblessures in de sport. Geneeskunde en Sport 2005; 38: 179-185