Knees are something of a hot topic in the studio at the moment. I thought you might benefit from understanding their anatomy, typical problems, why they occur and tips for maintaining knee health.
The knee is one of the largest and most complex joints in the body. It is a synovial joint which connects the femur (thigh bone) and the tibia (shin bone) in the lower leg (tibiofemoral joint). The fibula (calf bone), the other bone in the lower leg is connected to the joint but is not directly affected by the joint action. There is a second joint where the knee cap meets the femur ( patellofemoral joint). These two joints work together to form a modified hinge joint that allows the knee to bend and extend, but also rotate slightly from side to side.
Within the knee joint, the two knobbly ends of the femur are covered in articular cartilage. Also within the knee joint, the top of the tibia is made up of two plateaus which are covered in articular cartilage. Attached are two concave pads of shock-absorbing cartilage, called menisci, which minimise the friction created at the meeting ends of the tibia and femur. The patellar tendon attaches the knee cap to the tibia, it is a continuation of the quadriceps tendon.
The patella (knee cap) is a semi-flat triangular bone that is able to move as the knee bends. Its main job is to increase the force generated by the quadriceps muscle, which straightens/extends the knee. Its other job is to protect the knee joint from trauma. The knee cap glides within a groove formed between the knobbly ends of the femur.
Four key ligaments connect the bones in the knee, they work together in controlling the stability of the knee:-
- Medial collateral ligament (MCL) – limits the sideways motion of the knee.
- Lateral collateral ligament (LCL) – limits sideways motion of your knee.
- Anterior cruciate ligament (ACL) – limits forward motion of the tibia relative to the femur; also limits some rotation and sideways motion of the knee.
- Posterior cruciate ligament (PCL) – limits backward motion of the tibia relative to the femur; also limits some rotation and sideways motion of the knee.
- The cruciate ligaments criss-cross each other in the centre of the knee, allowing swing without too much forward or backward movement.
- Around the knee joint is a thick, fibrous structure, the joint capsule. Inside the capsule is the synovial membrane which is lined with synovium, a soft tissue structure that secretes synovial fluid, the lubricant of the knee.
Muscles Around the Knee
Two main muscles groups keep the knee stable, well aligned and mobile.
- The quadriceps, a group of 4 muscles on the front of the thigh responsible for straightening the knee.
- The hamstrings, a group of 3 muscles at the back of the thigh responsible for bending the knee.
- The Iliotibial band is a broad tendinous extension of the tensor fascia late and gluteus maximus that also help to stabilise the knee.
Bursae are fluid filled sacs that cushion a joint by reducing friction between muscles, bones, tendons and ligaments. There are around 13 of these, in varying sizes, in and around the knee. Sometimes, whether due to direct trauma, or infection, these can become irritated, swollen and painful, a condition known as bursitis.
Problems in the Knee
Our knees are vulnerable to injury because they bear an enormous amount of pressure whilst providing flexible movement. Consider the load whilst performing these activities:
- Walking = 1.5 x body weight
- Climbing Stairs = 3-4 x body weight
- Performing Squats = 8 x body weight
As you can see, there are many structures associated with the knee where problems can occur. Symptoms can vary depending on whether it is a wear and tear issue or an injury. Ligament injuries tend to lead to instability in the joint, whereas arthritis tends to decrease the range of motion. Swelling, the accumulation of too much synovial fluid, is usually due to irritation or inflammation of structures within the knee. Bleeding in the joint can also cause swelling, such as immediately after an injury. Best dealt with by REST – ICE – COMPRESSION – ELEVATION (R.I.C.E)
Another common condition is Runner’s Knee, but it isn’t only runners that suffer from this. This condition covers a broad range of problems; symptoms include pain in the front of your knee cap, but can also be around or behind it; pain when you bend your knee or walk down stairs or downhill. Clinicians call it Patellofemoral Syndrome and it can be caused by:-
- high stress exercises like lunges
- a direct hit to the knee
- poor alignment of any of the bones from your hips to your ankles
- problems with your feet such as hyper-mobility, fallen arches, over-pronation (foot rolling down and inwards when you step)
- weak or unbalanced thigh muscles, leading to incorrect tracking of the knee cap
- breakdown in the cartilage under the knee cap (Chondromalacia Patella)
Keeping your Knees Healthy
- Maintain a healthy Weight – each additional kg you carry translates into 4 kg of pressure on the knee.
- Review and un-process your diet to lower inflammation; Boost consumption of Omega-3 and green leafy vegetables.
- Be honest about your posture and alignment, then resolve to take action to improve both.
- Move more – this is the golden rule for all joint health, not just knees.
- Pay attention to your flexibility and increase the range of motion if your knees do not fully straighten. Stretch daily or at least 3 times per week.
- If you are hyper-mobile increase core and joint stability, paying attention to how you transfer forces like gravity and body-weight.
- Safety first – warm up and mobilise your joints before exercise.
- Know your limits – Exercise is great, but so is knowing when to stop; injuring your knee is much more likely if you are tired.
- Strengthen the muscles that stabilise the knee joint to help absorb the stress you place on the knee. Not only Quads and Hamstrings, but also the muscles around the hip and your core. This is best done under the guidance of an experienced instructor.
- Don’t self medicate – the shops are full of supplements that promise to relieve joint pain, not all are safe or well researched. Talk to your doctor or visit a qualified nutritionist.
- Don’t ignore injuries – see your doctor or a physical therapist. Taking early action can avoid more damage.
If you suffer from Arthritis avoid standing on hard surfaces for extended period of time. Also avoid deep bending of your knees and high impact sports such as jogging or anything that involves jumping. Instead go for low impact exercise like cycling, swimming or using an elliptical trainer.