“Patellofemoral” Pain (PFP) is a term often used to describe “non specific” pain or soreness under and/or around the kneecap and is one of the more common sources of knee pain among active and non-active people in all age groups; females experience patellofemoral pain approximately twice as often as males. PFP is often called “Runner’s Knee” because of the prevalence among joggers.
Anatomy and Function
The knee is a large and complex joint that includes the thigh bone (femur), shin bone (tibia) and knee cap (patella). The patella is a large sesamoid bone within the tendon of the thigh muscle (quadriceps femoris muscle group) as it crosses over and in front of the knee joint to attach onto the upper front portion of the tibia. The knee cap sits within a “groove” (the trochlea) at the bottom end of the femur and forms its own joint that is referred to as the “patellofemoral joint”. When the knee bends (flexes) and straightens (extends), the kneecap glides up and down this groove. The function of the patella is to provide leverage and increase the mechanical advantage of the quadriceps muscle; without it we would lose 50% of our knee extension strength. The patella also helps protect the front of the knee from trauma.
Symptoms of patellofemoral pain are typically described as a ‘dull’ or ‘sharp’ ache or pain ‘under’ or ‘around’ the kneecap. Activities most commonly associated with PFP include squatting, walking up or down stairs, running, and sitting for long periods of time. Localized pain above or below the kneecap is often tendonitis or tendonosis and instability of the knee may be symptoms of a cartilage or ligament injury. Other diagnoses that need to be considered and ruled out include chondromalacia patellae (a “softening” or degeneration of the cartilage under the knee cap), arthritis, and plica among others so it is important to see a qualified medical professional for accurate diagnosis.
Patellofemoral pain is believed to be caused by abnormal tracking of the kneecap and can be the result of a number of factors including muscle tightness, weakness and “overuse”. Individual anatomical factors and improper equipment fit also contribute to PFP.
Muscle tightness and/or weakness can alter the line of pull directly or by promoting excessive adduction and internal rotation of the femur. The muscle group affecting patellar tracking most directly is the quadriceps (femoris), but the iIiotibial band, hip extensors, abductors, adductors, hamstrings, and calf muscles also influence patellar tracking. Tight and weak musculature of the lower leg muscles and/or excessive foot pronation can also stress the patella via excessive internal rotation of the tibia.
“Overuse” simply refers to “doing too much too soon” or continually performing a movement or activity the body or body part isn’t prepared for. When the physical demand is greater than tissue tolerance without adequate recovery, inflammation, pain and injury often results. This applies to any repetitive activity as well as sports and training.
“Training errors” are probably the number one cause of overuse injury among athletes or anyone participating in a regular training program. The more common “errors” that lead to injury involve the mismanagement of the frequency, volume, intensity and recovery within a training program. These variables are a part of every training program and need to be manipulated individually and as a group in a way that allows the body to develop a “tolerance” to the activity so progression can occur without injury.
Other training errors commonly seen with patellofemoral pain are lower extremity workouts that don’t utilize proper warm up, flexibility, strength, and technique. For example, if you are new to strength training start light, not heavy; if you perform squats, start with partial squats, not full. If you’re a beginning runner, start with a walk/jog program and progress mileage slowly. Don’t start with sprint workouts or hill repeats until you have built a solid foundation of strength and endurance. If you miss more than a few workouts, don’t start where you left off, but instead reduce the volume and intensity appropriately and work your way back into shape. Learn proper technique with all exercises and be consistent with your training program.
Anatomical risk factors that contribute to PFP include leg length discrepancies, flat feet (pes planus), high arches (pes cavus), and a knee cap that sits either too high or too low in relation to its optimal position in the femoral groove. A wide pelvic girdle can create a patellar alignment problem by pulling the kneecap too far to the outside and “off track”. This is known as the Q-angle effect and is more common in females than males. Improper equipment fit such as footwear and bike fit also contribute to excessive stress on the patellofemoral joint.
As with any injury, effective treatment starts with proper diagnosis. Treatment of patellofemoral pain starts with activity modification or total rest and ice, depending on the severity of the injury. Ice is an effective, inexpensive natural anti-inflammatory and analgesic and can be used whenever there is pain, no matter if it’s a day or few months after the injury.
If you spend most of the day sitting, try to frequently change the position of your knees from straight to no more than 90 degrees of bend. Any one position for a prolonged length of time can aggravate PFP. During acute periods of pain, try to avoid stairs and unnecessary squatting. Whether or not you’re a runner, replace worn shoes. Consider a replacement insole in all shoes as improved shock absorption and support has been shown to reduce PFP. If you’re a cyclist a bike fit will help reduce unnecessary patellofemoral stress while maximizing efficiency and power.
Gentle stretching and mobility exercises should be started as soon as tolerated and include most muscles of the hip, thigh and calf. Stretching improves patellar alignment and reduces compression forces on the kneecap. Follow this with appropriate strengthening of the same muscle groups and a gradual return to training. Strength promotes proper alignment and improved ability of all muscles and joints to absorb and distribute forces.
Before you resume training, analyze your program and identify and address any mobility and strength imbalances that might contribute to dysfunctional movement patterns and poor mechanics and be sure to include muscles of the core, hip and lower leg as well as the thigh. Evaluate and address the variables of frequency, volume, intensity and recovery within your program to avoid any training errors that might have contributed to the injury.
When you start training again, be careful not to resume training where you left off. Depending on how much time you missed, you may need to start at 25% – 50% or more of your usual program and increase 10% or so a week from there or as instructed by your physical therapist, doctor or coach. Be sure to include adequate warm up and recovery within and between workouts.
As with most injuries, the best preventive advice can be summed up in what I refer to as the PETR Principles© which includes proper Preparation, Equipment, Technique and Recovery.
Preparation: the goal of preparation is to increase the bodies’ physiological tolerance so the demand of any particular sport or activity does not break it down to the point of injury. The better prepared the body is, the more resistant it is to stress and injury. Preparation includes appropriate warm up, flexibility, strength, endurance and balance training and is a must for those that participate in any sport. Adequate flexibility and strength of the hip, thigh and calf muscles are important because these help control patellar alignment and reduce excessive adduction and internal rotation of the thigh (femur) and internal rotation of the shin (tibia). The hip adductors, abductors and external rotators are important because they control adduction and internal rotation of the thigh and lower leg, which can also influence pronation of the foot.
Equipment specific to patellofemoral pain includes footwear and bike fit. Activity specific footwear is important for appropriate support, shock absorption and fit. For example, don’t jog in a shoe designed for tennis or basketball because ‘court’ shoes are not engineered for the mileage and steady state impact of jogging. If you’re on your feet all day be sure to wear a shoe that offers good support, shock absorption and fits well.
Cycling involves repetitive movement of the legs through a relatively large range of motion, against a resistance, and takes place while sitting on a fixed seat leaning forward. This posture creates a specific geometry between the body and the bike and if not fit correctly can cause excessive stress on the knees, hips and back. On the other hand, when fit correctly, this geometry can be optimized to produce the least amount of stress while maximizing force production.
Technique refers to movement patterns required to perform an activity or sport efficiently and successfully. Generally speaking, the better the technique, the less the risk is of injury and the more successful the result.
For runners, a good example of technique is cadence. Simply stated, cadence is the number of steps taken per unit of time, usually one minute. Runners with a higher cadence (~180 steps per minute and higher) have a shorter stride and a foot-strike that that is more beneath their hips. This creates less impact forces and improves efficiency compared to those with a lower cadence (~160 to 170 steps per minute). Beginner and less experienced runners tend to over-stride which produces more impact force and stress on the knees as well as the feet, hips and back. Proper technique is important and can be learned with any movement or sport.
Recovery is necessary for physiologic adaptation to occur. Adaptation is how the body develops strength and endurance and it is during rest and recovery the body repairs and regenerates. Recovery can include easy training days, complete days off and sleep. As the volume and intensity of the workouts increases, so do our sleep and recovery needs. Without adequate rest and sleep we lose fitness. Recovery is the key to getting stronger and faster. Strength is gained during recovery periods, not during the actual work out.
Bottom line: the principles of proper preparation, equipment, technique and recovery will help prevent overuse and potential injury of the patellofemoral joint.
Partial list of references
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