By Robert Barker Physiotherapist.
What is a Rectus Femoris Strain
The rectus femoris muscle is your largest quadricep muscle, which runs down the front of your thigh. The muscle originates at the front of pelvis and inserts via the quadriceps and patella tendon, just below your knee. It is a very powerful muscle which acts to extend the knee joint and flex the hip. Actions such as kicking, jumping and sprinting which all require very large force production rely heavily on the rectus femoris muscle.
There are two types of rectus femoral strains, the more common being a proximal strain at the muscle-tendon junction just below the hip, and the less common being a distal strain at the muscle-tendon junction just above the knee.
Proximal strains occur where the powerful rectus femoris muscle starts to lead into the tendon. Explosive contraction of the muscle creates a very high force production at the muscle-tendon junction creating the muscle to tear or even completely rupture. The muscle can also tear gradually over a long period of time due to micro-tears and chronic tendon inflammation. This occurs through overuse, overtraining, and overloading the muscle (too much or too hard to soon). If the tendon is inflamed, this is diagnosed as a tendinopathy, which can be harder to treat and recover from.
Symptoms / characteristics
In an acute tear of the rectus femoris muscle, symptoms will include:
- Sharp pain at the front of the hip or thigh.
- The will become swollen and substantial bruising may occur if it’s a high-grade tear.
- The area will be tender to touch, and a palpable and visible deformity (cavity) may be present.
- A feeling of weakness and/or heaviness when trying to extend your knee or lift your leg up.
- If it’s a complete rupture of the tendon/muscle then you will not be able to contract the muscle. You may have a deep sensation of ripping or tearing and the muscle may recoil and ‘bunch’ in the middle of your thigh. There also may be very little pain with a full rupture.
Acute tears are graded from 1 to 3 depending on severity:
Grade 1 is categorised as mild pain and a feeling of tightness. There is normally no swelling, only an area of increase muscle tension. Usually you will be able to continue with activity/exercise with a grade 1 strain and recovery will take 1-2 weeks.
Grade 2 strains involve a sudden strong pain, which stops you from continuing activity. Bruising and swelling will appear in your upper thigh, with increased pain when straitening the leg and walking. Recovery will take approximately 4-6 weeks.
Grade 3 tears involve severe pain and tearing sensation. Usually you will not be able to walk, and severe swelling and wide spread dark bruising will appear. Contraction of the quadriceps muscles will be difficult and very painful, and a noticeable muscle deformity will be visible. If it is a complete rupture, then following the initial injury, very little pain may be felt. Recovery will take approximately 9-12 weeks.
In a chronic tear or tendinopathy, symptoms may include:
- gradual onset of pain and tenderness in the upper thigh.
- Pain with sudden movements, such as lifting the knee up, kicking, jumping, and performing a strait leg raise.
- Pain and muscle stiffness is usually delayed, and worse after periods of activity, sitting for long periods, and first thing in the morning.
Recovery from a rectus femoris tendinopathy is very variable as there are many extrinsic and intrinsic factors at play. Also, it depends on how long and what stage of tendinopathy you have. For example, a reactive tendon can take 2-3 months to rehabilitate whereas a degenerative tendon can take years to fully recovery from.
The main causes and mechanisms of rectus femoris strains are:
- A rapid deceleration of the muscle following a powerful contraction such as kicking.
- A very fast and powerful contraction of the muscle such as jumping.
- A sudden and powerful eccentric contraction (lengthening) of the muscle, such as landing, fast changes direction on an already flexed knee and the back-swing phase of sprinting.
Studies have shown that muscle groups that cross two or more joints, have a large amount of powerful fast twitch (type II) fibres, and muscles with large musculotendon junctions are at a greater risk of strains. The rectus femoris muscle has all of these attributes.
Muscle fatigue also plays a role in acute muscle tears and strains, and given the heavy workload of the quadriceps muscles in running and kicking based sports it is easy to see why it is a very common injury.