Lower back, shoulder and knee are the big three "injury"' joints for active people. Even the inactive will inevitably have mild or serious injury to one or more of these joints over a lifetime. Knee injuries, especially to the knee ligaments, are exceedingly common in sporting communities. Knee injuries can result in pain, swelling and immobility from minor to severe in effect.
For weight trainers and physically active men and women, the knee joints endure a wide range of stresses and strains. For the most part, in younger years, the knee joints serve us well. However, in sports with twisting movements -- such as football, basketball, hockey and many others -- ligaments that bind the complex bones of the knee joint together can be damaged, often severely. In addition, as we age, normal wear and tear can result in osteoarthritis of the knee joints. In this condition, cartilage that provides cushioning between bones deteriorates and causes bones to rub together resulting in pain and stiffness.
Weight Training and Knee Injuries
While it may seem like weight training could contribute to knee injuries, this is not the case. Lifts like deadlifts and squats do place high forces on the knee joints, but these forces are applied mostly vertically and not horizontally or rotationally (twisting). The knees cope with vertical forces much better than high-impact horizontal and twisting forces. Even so, knee injuries do occur in weight training and in the very high forces of Olympic weightlifting, and if you have an existing knee injury from another activity, inappropriate weight training exercises could make it worse. In each of the knee ligament injures below, the damage can range from a sprain to a slight tear or a complete tear in the most serious cases. Here's what you need to know.
Common Types of Knee Injuries
Anterior Cruciate Ligament (ACL). This ligament ties the femur bone of the thigh to the tibia or shin bone of the lower leg and controls excessive rotation or extension of the knee joint. Anterior means at the front. A rear (posterior) ligament is also present. ACL injuries are seen mostly in athletes. Severe damage to the ACL usually means surgical reconstruction and up to 12 months rehabilitation. In the gym, be careful not to allow twisting knee movements under excessive load, intentionally or accidentally.
Posterior Cruciate Ligament (PCL). The PCL connects the femur and tibia at different point to the ACL and control any rearward motion of the tibia at the joint. The PCL is mostly injured with high-impact forces as a result of accidents, and sometimes in sports activities where a sharp blow to the knee occurs.
Medial Collateral Ligament (MCL). This ligament keeps the knee from bending too far to the inside (medially). Damaged MCLs mostly occur from an impact to the outside of the knee, or even from an accidental bodyweight force when the leg reaches an unusual angle.
Lateral Collateral Ligament (LCL). This is the opposite ligament to the MCL. It's on the outside of the knee and controls excessive movement outward. This ligament connects the fibula (the smaller bone of the lower leg) to the femur. Similarly, the LCL is injured when a force pushes the knee outward.
Cartilage Injury. Cartilage prevents bones rubbing together and cushions impacts. The two knee menisci (meniscus single) are cartilages that cushion the inside and outside of the knee joint. Other types of cartilage protect the ends of the thigh and shin bones. When cartilage is torn or damaged, surgery with an arthroscope may be necessary. (An arthroscope is an implement that allows a surgeon to see and fix cartilage injuries with a small incision.)
Tendonitis. Aggravated and overused tendons of the knee can cause disabling knee injuries. A related injury called "illiotibial band syndrome" (ITB) causes pain to the outside of the knee, often in runners, but it can occur in any overuse situation. Rest and stretching and anti-inflammatory medication is often recommended for these types of injures.
Weight Training Exercises to Avoid
If you have an existing knee injury, take the advice of your doctor or physical therapist in the first instance. Gym exercises that may be best avoided are the isolation exercises like the leg extension machine, and the leg curl exercises, either standing or on a bench. In addition, heavy loads or deep squats should mostly be avoided.