The Royal Guardians of Knee Health

Surfing - World Surf League - France’s Vahine Fierro in action during the women’s quarter-finals heat 3 REUTERS/Thomas Bevilacqua

Knee joint health is crucial for athletes, significantly affecting their performance and overall mobility. Protecting knee health is essential to prevent long-term complications such as osteoarthritis (OA) and to maintain the quality of life and function. Clinicians must prioritize joint protection during rehabilitation, focus on resolving effusions, and emphasize quadriceps strength to safeguard athletes’ knee health.

Athletes often struggle with the idea of life beyond their sport, particularly when knee injuries impact their ability to participate. Comments like "I don’t run anymore, my knees are ruined" highlight the long-term consequences of knee injuries. These statements underscore the importance of protecting knee health to ensure athletes enjoy an active lifestyle even after their sports careers end.

Does Playing Sports Increase the Knee OA Risk?

Physical activity is essential for overall health. However, sports also carry risks of injury. These injuries may impact long-term quality of life; clinicians must manage them carefully. For example, football players who sustain knee injuries are at an increased risk of developing knee osteoarthritis compared to non-athletes⁽¹⁾. This risk is primarily driven by previous knee injuries rather than football participation⁽¹⁾. However, these results can probably be extended beyond football to all sports and knee injuries. Therefore, previous injury is the most significant risk factor for long-term sequelae.

Non-Time Loss Injuries

It is common for athletes to play with pain and niggles. Researchers at the University of Wollongong in Australia found that more than 25% of semi-professional footballers reported a physical complaint each week that did not prevent them from training or playing in matches⁽²⁾. However, these non-time loss injuries increase an athlete’s risk of subsequent time-loss injuries 3-7 times within seven days of participating with the niggle⁽²⁾. This highlights the importance of addressing all injuries, regardless of severity, to prevent further complications and ensure optimal recovery.

Arthrogenic Muscle Inhibition

Arthrogenic muscle inhibition is a complex neurological process that limits muscle activation following joint injury⁽³⁾. It is a critical factor in rehabilitation, impairing recovery and affecting long-term joint health. Furthermore, AMI involves a sequence of changes, including altered somatosensation, reflexive muscle inhibition, brain activity changes, and reduced muscle motor output⁽³⁾. This is evident in the typical quadriceps wasting following moderate to severe knee injuries. However, clinicians should be cautious with mild injuries as well. They must objectively assess and manage any effusions when managing all knee injuries, whether mild or severe. Importantly, the effusion grade is not correlated to the degree of inhibition⁽⁴⁾. Arthrogenic muscle inhibition is exacerbated by joint effusion, pain, and inflammation. Therefore, addressing these factors early in the rehabilitation process can mitigate the effects of AMI and promote effective recovery.

The quadriceps muscle is vital for protecting knee joint health. Higher quadriceps and vastus medialis muscle volumes are associated with less severe knee cartilage abnormalities and lower bone marrow edema-like lesions⁽⁵⁾. A higher quadriceps ratio to total muscle volume correlates with lower WOMAC (Osteoarthritis Index) pain scores⁽⁵⁾. Therefore, enhancing quadriceps strength is crucial for preventing knee-related issues and maintaining overall knee function, particularly following injury. Any deficits enhance the risk of quality of life deterioration later in life.

Quadriceps muscle mass, strength, and power are critical for overall physical performance and quality of life. Age-associated declines in these areas can increase the fear of falling and reduce functional independence in older adults⁽⁶⁾. Improving quadriceps strength can significantly lower the risk of becoming dependent on activities of daily living (ADL). For example, researchers at the University of Maastricht in the Netherlands found that enhancing quadriceps strength by just 1 kg can reduce the risk of ADL dependency by 65%⁽⁷⁾. Therefore, focusing on muscle strength and power is essential for maintaining independence. Clinicians should focus on improving quadriceps strength when designing rehabilitation programs, as minor improvements have exponential gains. Furthermore, when working with athletes with performance outcomes, maintaining quadriceps strength is vital for preserving joint health during competition.

Varied training methods, such as blood flow restriction and rest-pause training, are available to aid recovery. Researchers in Belgium conducted a systematic review and meta-analysis to examine the effects of low-load resistance training combined with blood flow restriction (LL-BFR) versus conventional quadriceps strengthening on knee symptoms, function, strength, and muscle thickness in adults with knee conditions. They concluded that LL-BFR is potentially more beneficial for quadriceps strength and muscle thickness and equally effective for improving function with less knee pain than conventional high-load training, suggesting its utility in rehabilitation where conventional methods exacerbate symptoms⁽⁸⁾. Rest-pause training is a strength training technique that involves breaking a set into multiple mini-sets with short rest intervals in between. Depending on the training objective, it can be used for strength (intensity) and hypertrophy (volume).